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INFO-DIR-SECTION Software development
START-INFO-DIR-ENTRY
* gfortran: (gfortran). The GNU Fortran Compiler.
END-INFO-DIR-ENTRY
This file documents the use and the internals of the GNU Fortran
compiler, (`gfortran').
Published by the Free Software Foundation 51 Franklin Street, Fifth
Floor Boston, MA 02110-1301 USA
Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
2008, 2009, 2010 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
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Invariant Sections being "Funding Free Software", the Front-Cover Texts
being (a) (see below), and with the Back-Cover Texts being (b) (see
below). A copy of the license is included in the section entitled "GNU
Free Documentation License".
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.

File: gfortran.info, Node: Top, Next: Introduction, Up: (dir)
Introduction
************
This manual documents the use of `gfortran', the GNU Fortran compiler.
You can find in this manual how to invoke `gfortran', as well as its
features and incompatibilities.
* Menu:
* Introduction::
Part I: Invoking GNU Fortran
* Invoking GNU Fortran:: Command options supported by `gfortran'.
* Runtime:: Influencing runtime behavior with environment variables.
Part II: Language Reference
* Fortran 2003 and 2008 status:: Fortran 2003 and 2008 features supported by GNU Fortran.
* Compiler Characteristics:: User-visible implementation details.
* Mixed-Language Programming:: Interoperability with C
* Extensions:: Language extensions implemented by GNU Fortran.
* Intrinsic Procedures:: Intrinsic procedures supported by GNU Fortran.
* Intrinsic Modules:: Intrinsic modules supported by GNU Fortran.
* Contributing:: How you can help.
* Copying:: GNU General Public License says
how you can copy and share GNU Fortran.
* GNU Free Documentation License::
How you can copy and share this manual.
* Funding:: How to help assure continued work for free software.
* Option Index:: Index of command line options
* Keyword Index:: Index of concepts

File: gfortran.info, Node: Introduction, Next: Invoking GNU Fortran, Prev: Top, Up: Top
1 Introduction
**************
The GNU Fortran compiler front end was designed initially as a free
replacement for, or alternative to, the unix `f95' command; `gfortran'
is the command you'll use to invoke the compiler.
* Menu:
* About GNU Fortran:: What you should know about the GNU Fortran compiler.
* GNU Fortran and GCC:: You can compile Fortran, C, or other programs.
* Preprocessing and conditional compilation:: The Fortran preprocessor
* GNU Fortran and G77:: Why we chose to start from scratch.
* Project Status:: Status of GNU Fortran, roadmap, proposed extensions.
* Standards:: Standards supported by GNU Fortran.

File: gfortran.info, Node: About GNU Fortran, Next: GNU Fortran and GCC, Up: Introduction
1.1 About GNU Fortran
=====================
The GNU Fortran compiler supports the Fortran 77, 90 and 95 standards
completely, parts of the Fortran 2003 and Fortran 2008 standards, and
several vendor extensions. The development goal is to provide the
following features:
* Read a user's program, stored in a file and containing
instructions written in Fortran 77, Fortran 90, Fortran 95,
Fortran 2003 or Fortran 2008. This file contains "source code".
* Translate the user's program into instructions a computer can
carry out more quickly than it takes to translate the instructions
in the first place. The result after compilation of a program is
"machine code", code designed to be efficiently translated and
processed by a machine such as your computer. Humans usually
aren't as good writing machine code as they are at writing Fortran
(or C++, Ada, or Java), because it is easy to make tiny mistakes
writing machine code.
* Provide the user with information about the reasons why the
compiler is unable to create a binary from the source code.
Usually this will be the case if the source code is flawed. The
Fortran 90 standard requires that the compiler can point out
mistakes to the user. An incorrect usage of the language causes
an "error message".
The compiler will also attempt to diagnose cases where the user's
program contains a correct usage of the language, but instructs
the computer to do something questionable. This kind of
diagnostics message is called a "warning message".
* Provide optional information about the translation passes from the
source code to machine code. This can help a user of the compiler
to find the cause of certain bugs which may not be obvious in the
source code, but may be more easily found at a lower level
compiler output. It also helps developers to find bugs in the
compiler itself.
* Provide information in the generated machine code that can make it
easier to find bugs in the program (using a debugging tool, called
a "debugger", such as the GNU Debugger `gdb').
* Locate and gather machine code already generated to perform
actions requested by statements in the user's program. This
machine code is organized into "modules" and is located and
"linked" to the user program.
The GNU Fortran compiler consists of several components:
* A version of the `gcc' command (which also might be installed as
the system's `cc' command) that also understands and accepts
Fortran source code. The `gcc' command is the "driver" program for
all the languages in the GNU Compiler Collection (GCC); With `gcc',
you can compile the source code of any language for which a front
end is available in GCC.
* The `gfortran' command itself, which also might be installed as the
system's `f95' command. `gfortran' is just another driver program,
but specifically for the Fortran compiler only. The difference
with `gcc' is that `gfortran' will automatically link the correct
libraries to your program.
* A collection of run-time libraries. These libraries contain the
machine code needed to support capabilities of the Fortran
language that are not directly provided by the machine code
generated by the `gfortran' compilation phase, such as intrinsic
functions and subroutines, and routines for interaction with files
and the operating system.
* The Fortran compiler itself, (`f951'). This is the GNU Fortran
parser and code generator, linked to and interfaced with the GCC
backend library. `f951' "translates" the source code to assembler
code. You would typically not use this program directly; instead,
the `gcc' or `gfortran' driver programs will call it for you.

File: gfortran.info, Node: GNU Fortran and GCC, Next: Preprocessing and conditional compilation, Prev: About GNU Fortran, Up: Introduction
1.2 GNU Fortran and GCC
=======================
GNU Fortran is a part of GCC, the "GNU Compiler Collection". GCC
consists of a collection of front ends for various languages, which
translate the source code into a language-independent form called
"GENERIC". This is then processed by a common middle end which
provides optimization, and then passed to one of a collection of back
ends which generate code for different computer architectures and
operating systems.
Functionally, this is implemented with a driver program (`gcc')
which provides the command-line interface for the compiler. It calls
the relevant compiler front-end program (e.g., `f951' for Fortran) for
each file in the source code, and then calls the assembler and linker
as appropriate to produce the compiled output. In a copy of GCC which
has been compiled with Fortran language support enabled, `gcc' will
recognize files with `.f', `.for', `.ftn', `.f90', `.f95', `.f03' and
`.f08' extensions as Fortran source code, and compile it accordingly. A
`gfortran' driver program is also provided, which is identical to `gcc'
except that it automatically links the Fortran runtime libraries into
the compiled program.
Source files with `.f', `.for', `.fpp', `.ftn', `.F', `.FOR',
`.FPP', and `.FTN' extensions are treated as fixed form. Source files
with `.f90', `.f95', `.f03', `.f08', `.F90', `.F95', `.F03' and `.F08'
extensions are treated as free form. The capitalized versions of
either form are run through preprocessing. Source files with the lower
case `.fpp' extension are also run through preprocessing.
This manual specifically documents the Fortran front end, which
handles the programming language's syntax and semantics. The aspects
of GCC which relate to the optimization passes and the back-end code
generation are documented in the GCC manual; see *Note Introduction:
(gcc)Top. The two manuals together provide a complete reference for
the GNU Fortran compiler.

File: gfortran.info, Node: Preprocessing and conditional compilation, Next: GNU Fortran and G77, Prev: GNU Fortran and GCC, Up: Introduction
1.3 Preprocessing and conditional compilation
=============================================
Many Fortran compilers including GNU Fortran allow passing the source
code through a C preprocessor (CPP; sometimes also called the Fortran
preprocessor, FPP) to allow for conditional compilation. In the case of
GNU Fortran, this is the GNU C Preprocessor in the traditional mode. On
systems with case-preserving file names, the preprocessor is
automatically invoked if the filename extension is `.F', `.FOR',
`.FTN', `.fpp', `.FPP', `.F90', `.F95', `.F03' or `.F08'. To manually
invoke the preprocessor on any file, use `-cpp', to disable
preprocessing on files where the preprocessor is run automatically, use
`-nocpp'.
If a preprocessed file includes another file with the Fortran
`INCLUDE' statement, the included file is not preprocessed. To
preprocess included files, use the equivalent preprocessor statement
`#include'.
If GNU Fortran invokes the preprocessor, `__GFORTRAN__' is defined
and `__GNUC__', `__GNUC_MINOR__' and `__GNUC_PATCHLEVEL__' can be used
to determine the version of the compiler. See *Note Overview: (cpp)Top.
for details.
While CPP is the de-facto standard for preprocessing Fortran code,
Part 3 of the Fortran 95 standard (ISO/IEC 1539-3:1998) defines
Conditional Compilation, which is not widely used and not directly
supported by the GNU Fortran compiler. You can use the program coco to
preprocess such files (`http://users.erols.com/dnagle/coco.html').

File: gfortran.info, Node: GNU Fortran and G77, Next: Project Status, Prev: Preprocessing and conditional compilation, Up: Introduction
1.4 GNU Fortran and G77
=======================
The GNU Fortran compiler is the successor to `g77', the Fortran 77
front end included in GCC prior to version 4. It is an entirely new
program that has been designed to provide Fortran 95 support and
extensibility for future Fortran language standards, as well as
providing backwards compatibility for Fortran 77 and nearly all of the
GNU language extensions supported by `g77'.

File: gfortran.info, Node: Project Status, Next: Standards, Prev: GNU Fortran and G77, Up: Introduction
1.5 Project Status
==================
As soon as `gfortran' can parse all of the statements correctly,
it will be in the "larva" state. When we generate code, the
"puppa" state. When `gfortran' is done, we'll see if it will be a
beautiful butterfly, or just a big bug....
-Andy Vaught, April 2000
The start of the GNU Fortran 95 project was announced on the GCC
homepage in March 18, 2000 (even though Andy had already been working
on it for a while, of course).
The GNU Fortran compiler is able to compile nearly all
standard-compliant Fortran 95, Fortran 90, and Fortran 77 programs,
including a number of standard and non-standard extensions, and can be
used on real-world programs. In particular, the supported extensions
include OpenMP, Cray-style pointers, and several Fortran 2003 and
Fortran 2008 features such as enumeration, stream I/O, and some of the
enhancements to allocatable array support from TR 15581. However, it is
still under development and has a few remaining rough edges.
At present, the GNU Fortran compiler passes the NIST Fortran 77 Test
Suite (http://www.fortran-2000.com/ArnaudRecipes/fcvs21_f95.html), and
produces acceptable results on the LAPACK Test Suite
(http://www.netlib.org/lapack/faq.html#1.21). It also provides
respectable performance on the Polyhedron Fortran compiler benchmarks
(http://www.polyhedron.com/pb05.html) and the Livermore Fortran Kernels
test
(http://www.llnl.gov/asci_benchmarks/asci/limited/lfk/README.html). It
has been used to compile a number of large real-world programs,
including the HIRLAM weather-forecasting code
(http://mysite.verizon.net/serveall/moene.pdf) and the Tonto quantum
chemistry package (http://www.theochem.uwa.edu.au/tonto/); see
`http://gcc.gnu.org/wiki/GfortranApps' for an extended list.
Among other things, the GNU Fortran compiler is intended as a
replacement for G77. At this point, nearly all programs that could be
compiled with G77 can be compiled with GNU Fortran, although there are
a few minor known regressions.
The primary work remaining to be done on GNU Fortran falls into three
categories: bug fixing (primarily regarding the treatment of invalid
code and providing useful error messages), improving the compiler
optimizations and the performance of compiled code, and extending the
compiler to support future standards--in particular, Fortran 2003 and
Fortran 2008.

File: gfortran.info, Node: Standards, Prev: Project Status, Up: Introduction
1.6 Standards
=============
* Menu:
* Varying Length Character Strings::
The GNU Fortran compiler implements ISO/IEC 1539:1997 (Fortran 95).
As such, it can also compile essentially all standard-compliant Fortran
90 and Fortran 77 programs. It also supports the ISO/IEC TR-15581
enhancements to allocatable arrays, and the OpenMP Application Program
Interface v2.5 (http://www.openmp.org/drupal/mp-documents/spec25.pdf)
specification.
In the future, the GNU Fortran compiler will also support ISO/IEC
1539-1:2004 (Fortran 2003) and future Fortran standards. Partial support
of that standard is already provided; the current status of Fortran 2003
support is reported in the *Note Fortran 2003 status:: section of the
documentation.
The next version of the Fortran standard (Fortran 2008) is currently
being developed and the GNU Fortran compiler supports some of its new
features. This support is based on the latest draft of the standard
(available from `http://www.nag.co.uk/sc22wg5/') and no guarantee of
future compatibility is made, as the final standard might differ from
the draft. For more information, see the *Note Fortran 2008 status::
section.
Additionally, the GNU Fortran compilers supports the OpenMP
specification (version 3.0,
`http://openmp.org/wp/openmp-specifications/').

File: gfortran.info, Node: Varying Length Character Strings, Up: Standards
1.6.1 Varying Length Character Strings
--------------------------------------
The Fortran 95 standard specifies in Part 2 (ISO/IEC 1539-2:2000)
varying length character strings. While GNU Fortran currently does not
support such strings directly, there exist two Fortran implementations
for them, which work with GNU Fortran. They can be found at
`http://www.fortran.com/iso_varying_string.f95' and at
`ftp://ftp.nag.co.uk/sc22wg5/ISO_VARYING_STRING/'.

File: gfortran.info, Node: Invoking GNU Fortran, Next: Runtime, Prev: Introduction, Up: Top
2 GNU Fortran Command Options
*****************************
The `gfortran' command supports all the options supported by the `gcc'
command. Only options specific to GNU Fortran are documented here.
*Note GCC Command Options: (gcc)Invoking GCC, for information on the
non-Fortran-specific aspects of the `gcc' command (and, therefore, the
`gfortran' command).
All GCC and GNU Fortran options are accepted both by `gfortran' and
by `gcc' (as well as any other drivers built at the same time, such as
`g++'), since adding GNU Fortran to the GCC distribution enables
acceptance of GNU Fortran options by all of the relevant drivers.
In some cases, options have positive and negative forms; the
negative form of `-ffoo' would be `-fno-foo'. This manual documents
only one of these two forms, whichever one is not the default.
* Menu:
* Option Summary:: Brief list of all `gfortran' options,
without explanations.
* Fortran Dialect Options:: Controlling the variant of Fortran language
compiled.
* Preprocessing Options:: Enable and customize preprocessing.
* Error and Warning Options:: How picky should the compiler be?
* Debugging Options:: Symbol tables, measurements, and debugging dumps.
* Directory Options:: Where to find module files
* Link Options :: Influencing the linking step
* Runtime Options:: Influencing runtime behavior
* Code Gen Options:: Specifying conventions for function calls, data layout
and register usage.
* Environment Variables:: Environment variables that affect `gfortran'.

File: gfortran.info, Node: Option Summary, Next: Fortran Dialect Options, Up: Invoking GNU Fortran
2.1 Option summary
==================
Here is a summary of all the options specific to GNU Fortran, grouped
by type. Explanations are in the following sections.
_Fortran Language Options_
*Note Options controlling Fortran dialect: Fortran Dialect Options.
-fall-intrinsics -ffree-form -fno-fixed-form
-fdollar-ok -fimplicit-none -fmax-identifier-length
-std=STD -fd-lines-as-code -fd-lines-as-comments
-ffixed-line-length-N -ffixed-line-length-none
-ffree-line-length-N -ffree-line-length-none
-fdefault-double-8 -fdefault-integer-8 -fdefault-real-8
-fcray-pointer -fopenmp -fno-range-check -fbackslash -fmodule-private
_Preprocessing Options_
*Note Enable and customize preprocessing: Preprocessing Options.
-cpp -dD -dI -dM -dN -dU -fworking-directory
-imultilib DIR -iprefix FILE -isysroot DIR
-iquote -isystem DIR -nocpp -nostdinc -undef
-AQUESTION=ANSWER -A-QUESTION[=ANSWER]
-C -CC -DMACRO[=DEFN] -UMACRO -H -P
_Error and Warning Options_
*Note Options to request or suppress errors and warnings: Error
and Warning Options.
-fmax-errors=N
-fsyntax-only -pedantic -pedantic-errors
-Wall -Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation
-Wconversion -Wimplicit-interface -Wimplicit-procedure -Wline-truncation
-Wintrinsics-std -Wsurprising -Wno-tabs -Wunderflow -Wunused-parameter
-Wintrinsics-shadow -Wno-align-commons
_Debugging Options_
*Note Options for debugging your program or GNU Fortran: Debugging
Options.
-fdump-parse-tree -ffpe-trap=LIST
-fdump-core -fbacktrace
_Directory Options_
*Note Options for directory search: Directory Options.
-IDIR -JDIR -fintrinsic-modules-path DIR
_Link Options_
*Note Options for influencing the linking step: Link Options.
-static-libgfortran
_Runtime Options_
*Note Options for influencing runtime behavior: Runtime Options.
-fconvert=CONVERSION -fno-range-check
-frecord-marker=LENGTH -fmax-subrecord-length=LENGTH
-fsign-zero
_Code Generation Options_
*Note Options for code generation conventions: Code Gen Options.
-fno-automatic -ff2c -fno-underscoring
-fwhole-file -fsecond-underscore
-fbounds-check -fcheck-array-temporaries -fmax-array-constructor =N
-fcheck=<ALL|ARRAY-TEMPS|BOUNDS|DO|MEM|POINTER|RECURSION>
-fmax-stack-var-size=N
-fpack-derived -frepack-arrays -fshort-enums -fexternal-blas
-fblas-matmul-limit=N -frecursive -finit-local-zero
-finit-integer=N -finit-real=<ZERO|INF|-INF|NAN|SNAN>
-finit-logical=<TRUE|FALSE> -finit-character=N
-fno-align-commons -fno-protect-parens
* Menu:
* Fortran Dialect Options:: Controlling the variant of Fortran language
compiled.
* Preprocessing Options:: Enable and customize preprocessing.
* Error and Warning Options:: How picky should the compiler be?
* Debugging Options:: Symbol tables, measurements, and debugging dumps.
* Directory Options:: Where to find module files
* Link Options :: Influencing the linking step
* Runtime Options:: Influencing runtime behavior
* Code Gen Options:: Specifying conventions for function calls, data layout
and register usage.

File: gfortran.info, Node: Fortran Dialect Options, Next: Preprocessing Options, Prev: Option Summary, Up: Invoking GNU Fortran
2.2 Options controlling Fortran dialect
=======================================
The following options control the details of the Fortran dialect
accepted by the compiler:
`-ffree-form'
`-ffixed-form'
Specify the layout used by the source file. The free form layout
was introduced in Fortran 90. Fixed form was traditionally used in
older Fortran programs. When neither option is specified, the
source form is determined by the file extension.
`-fall-intrinsics'
This option causes all intrinsic procedures (including the
GNU-specific extensions) to be accepted. This can be useful with
`-std=f95' to force standard-compliance but get access to the full
range of intrinsics available with `gfortran'. As a consequence,
`-Wintrinsics-std' will be ignored and no user-defined procedure
with the same name as any intrinsic will be called except when it
is explicitly declared `EXTERNAL'.
`-fd-lines-as-code'
`-fd-lines-as-comments'
Enable special treatment for lines beginning with `d' or `D' in
fixed form sources. If the `-fd-lines-as-code' option is given
they are treated as if the first column contained a blank. If the
`-fd-lines-as-comments' option is given, they are treated as
comment lines.
`-fdefault-double-8'
Set the `DOUBLE PRECISION' type to an 8 byte wide type. If
`-fdefault-real-8' is given, `DOUBLE PRECISION' would instead be
promoted to 16 bytes if possible, and `-fdefault-double-8' can be
used to prevent this. The kind of real constants like `1.d0' will
not be changed by `-fdefault-real-8' though, so also
`-fdefault-double-8' does not affect it.
`-fdefault-integer-8'
Set the default integer and logical types to an 8 byte wide type.
Do nothing if this is already the default. This option also
affects the kind of integer constants like `42'.
`-fdefault-real-8'
Set the default real type to an 8 byte wide type. Do nothing if
this is already the default. This option also affects the kind of
non-double real constants like `1.0', and does promote the default
width of `DOUBLE PRECISION' to 16 bytes if possible, unless
`-fdefault-double-8' is given, too.
`-fdollar-ok'
Allow `$' as a valid non-first character in a symbol name. Symbols
that start with `$' are rejected since it is unclear which rules to
apply to implicit typing as different vendors implement different
rules. Using `$' in `IMPLICIT' statements is also rejected.
`-fbackslash'
Change the interpretation of backslashes in string literals from a
single backslash character to "C-style" escape characters. The
following combinations are expanded `\a', `\b', `\f', `\n', `\r',
`\t', `\v', `\\', and `\0' to the ASCII characters alert,
backspace, form feed, newline, carriage return, horizontal tab,
vertical tab, backslash, and NUL, respectively. Additionally,
`\x'NN, `\u'NNNN and `\U'NNNNNNNN (where each N is a hexadecimal
digit) are translated into the Unicode characters corresponding to
the specified code points. All other combinations of a character
preceded by \ are unexpanded.
`-fmodule-private'
Set the default accessibility of module entities to `PRIVATE'.
Use-associated entities will not be accessible unless they are
explicitly declared as `PUBLIC'.
`-ffixed-line-length-N'
Set column after which characters are ignored in typical fixed-form
lines in the source file, and through which spaces are assumed (as
if padded to that length) after the ends of short fixed-form lines.
Popular values for N include 72 (the standard and the default), 80
(card image), and 132 (corresponding to "extended-source" options
in some popular compilers). N may also be `none', meaning that
the entire line is meaningful and that continued character
constants never have implicit spaces appended to them to fill out
the line. `-ffixed-line-length-0' means the same thing as
`-ffixed-line-length-none'.
`-ffree-line-length-N'
Set column after which characters are ignored in typical free-form
lines in the source file. The default value is 132. N may be
`none', meaning that the entire line is meaningful.
`-ffree-line-length-0' means the same thing as
`-ffree-line-length-none'.
`-fmax-identifier-length=N'
Specify the maximum allowed identifier length. Typical values are
31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008).
`-fimplicit-none'
Specify that no implicit typing is allowed, unless overridden by
explicit `IMPLICIT' statements. This is the equivalent of adding
`implicit none' to the start of every procedure.
`-fcray-pointer'
Enable the Cray pointer extension, which provides C-like pointer
functionality.
`-fopenmp'
Enable the OpenMP extensions. This includes OpenMP `!$omp'
directives in free form and `c$omp', `*$omp' and `!$omp'
directives in fixed form, `!$' conditional compilation sentinels
in free form and `c$', `*$' and `!$' sentinels in fixed form, and
when linking arranges for the OpenMP runtime library to be linked
in. The option `-fopenmp' implies `-frecursive'.
`-fno-range-check'
Disable range checking on results of simplification of constant
expressions during compilation. For example, GNU Fortran will give
an error at compile time when simplifying `a = 1. / 0'. With this
option, no error will be given and `a' will be assigned the value
`+Infinity'. If an expression evaluates to a value outside of the
relevant range of [`-HUGE()':`HUGE()'], then the expression will
be replaced by `-Inf' or `+Inf' as appropriate. Similarly, `DATA
i/Z'FFFFFFFF'/' will result in an integer overflow on most
systems, but with `-fno-range-check' the value will "wrap around"
and `i' will be initialized to -1 instead.
`-std=STD'
Specify the standard to which the program is expected to conform,
which may be one of `f95', `f2003', `f2008', `gnu', or `legacy'.
The default value for STD is `gnu', which specifies a superset of
the Fortran 95 standard that includes all of the extensions
supported by GNU Fortran, although warnings will be given for
obsolete extensions not recommended for use in new code. The
`legacy' value is equivalent but without the warnings for obsolete
extensions, and may be useful for old non-standard programs. The
`f95', `f2003' and `f2008' values specify strict conformance to
the Fortran 95, Fortran 2003 and Fortran 2008 standards,
respectively; errors are given for all extensions beyond the
relevant language standard, and warnings are given for the Fortran
77 features that are permitted but obsolescent in later standards.

File: gfortran.info, Node: Preprocessing Options, Next: Error and Warning Options, Prev: Fortran Dialect Options, Up: Invoking GNU Fortran
2.3 Enable and customize preprocessing
======================================
Preprocessor related options. See section *Note Preprocessing and
conditional compilation:: for more detailed information on
preprocessing in `gfortran'.
`-cpp'
`-nocpp'
Enable preprocessing. The preprocessor is automatically invoked if
the file extension is `.fpp', `.FPP', `.F', `.FOR', `.FTN',
`.F90', `.F95', `.F03' or `.F08'. Use this option to manually
enable preprocessing of any kind of Fortran file.
To disable preprocessing of files with any of the above listed
extensions, use the negative form: `-nocpp'.
The preprocessor is run in traditional mode, be aware that any
restrictions of the file-format, e.g. fixed-form line width, apply
for preprocessed output as well.
`-dM'
Instead of the normal output, generate a list of `'#define''
directives for all the macros defined during the execution of the
preprocessor, including predefined macros. This gives you a way of
finding out what is predefined in your version of the preprocessor.
Assuming you have no file `foo.f90', the command
touch foo.f90; gfortran -cpp -dM foo.f90
will show all the predefined macros.
`-dD'
Like `-dM' except in two respects: it does not include the
predefined macros, and it outputs both the `#define' directives
and the result of preprocessing. Both kinds of output go to the
standard output file.
`-dN'
Like `-dD', but emit only the macro names, not their expansions.
`-dU'
Like `dD' except that only macros that are expanded, or whose
definedness is tested in preprocessor directives, are output; the
output is delayed until the use or test of the macro; and
`'#undef'' directives are also output for macros tested but
undefined at the time.
`-dI'
Output `'#include'' directives in addition to the result of
preprocessing.
`-fworking-directory'
Enable generation of linemarkers in the preprocessor output that
will let the compiler know the current working directory at the
time of preprocessing. When this option is enabled, the
preprocessor will emit, after the initial linemarker, a second
linemarker with the current working directory followed by two
slashes. GCC will use this directory, when it's present in the
preprocessed input, as the directory emitted as the current
working directory in some debugging information formats. This
option is implicitly enabled if debugging information is enabled,
but this can be inhibited with the negated form
`-fno-working-directory'. If the `-P' flag is present in the
command line, this option has no effect, since no `#line'
directives are emitted whatsoever.
`-idirafter DIR'
Search DIR for include files, but do it after all directories
specified with `-I' and the standard system directories have been
exhausted. DIR is treated as a system include directory. If dir
begins with `=', then the `=' will be replaced by the sysroot
prefix; see `--sysroot' and `-isysroot'.
`-imultilib DIR'
Use DIR as a subdirectory of the directory containing
target-specific C++ headers.
`-iprefix PREFIX'
Specify PREFIX as the prefix for subsequent `-iwithprefix'
options. If the PREFIX represents a directory, you should include
the final `'/''.
`-isysroot DIR'
This option is like the `--sysroot' option, but applies only to
header files. See the `--sysroot' option for more information.
`-iquote DIR'
Search DIR only for header files requested with `#include "file"';
they are not searched for `#include <file>', before all directories
specified by `-I' and before the standard system directories. If
DIR begins with `=', then the `=' will be replaced by the sysroot
prefix; see `--sysroot' and `-isysroot'.
`-isystem DIR'
Search DIR for header files, after all directories specified by
`-I' but before the standard system directories. Mark it as a
system directory, so that it gets the same special treatment as is
applied to the standard system directories. If DIR begins with
`=', then the `=' will be replaced by the sysroot prefix; see
`--sysroot' and `-isysroot'.
`-nostdinc'
Do not search the standard system directories for header files.
Only the directories you have specified with `-I' options (and the
directory of the current file, if appropriate) are searched.
`-undef'
Do not predefine any system-specific or GCC-specific macros. The
standard predefined macros remain defined.
`-APREDICATE=ANSWER'
Make an assertion with the predicate PREDICATE and answer ANSWER.
This form is preferred to the older form -A predicate(answer),
which is still supported, because it does not use shell special
characters.
`-A-PREDICATE=ANSWER'
Cancel an assertion with the predicate PREDICATE and answer ANSWER.
`-C'
Do not discard comments. All comments are passed through to the
output file, except for comments in processed directives, which
are deleted along with the directive.
You should be prepared for side effects when using `-C'; it causes
the preprocessor to treat comments as tokens in their own right.
For example, comments appearing at the start of what would be a
directive line have the effect of turning that line into an
ordinary source line, since the first token on the line is no
longer a `'#''.
Warning: this currently handles C-Style comments only. The
preprocessor does not yet recognize Fortran-style comments.
`-CC'
Do not discard comments, including during macro expansion. This is
like `-C', except that comments contained within macros are also
passed through to the output file where the macro is expanded.
In addition to the side-effects of the `-C' option, the `-CC'
option causes all C++-style comments inside a macro to be
converted to C-style comments. This is to prevent later use of
that macro from inadvertently commenting out the remainder of the
source line. The `-CC' option is generally used to support lint
comments.
Warning: this currently handles C- and C++-Style comments only. The
preprocessor does not yet recognize Fortran-style comments.
`-DNAME'
Predefine name as a macro, with definition `1'.
`-DNAME=DEFINITION'
The contents of DEFINITION are tokenized and processed as if they
appeared during translation phase three in a `'#define'' directive.
In particular, the definition will be truncated by embedded newline
characters.
If you are invoking the preprocessor from a shell or shell-like
program you may need to use the shell's quoting syntax to protect
characters such as spaces that have a meaning in the shell syntax.
If you wish to define a function-like macro on the command line,
write its argument list with surrounding parentheses before the
equals sign (if any). Parentheses are meaningful to most shells,
so you will need to quote the option. With sh and csh,
`-D'name(args...)=definition'' works.
`-D' and `-U' options are processed in the order they are given on
the command line. All -imacros file and -include file options are
processed after all -D and -U options.
`-H'
Print the name of each header file used, in addition to other
normal activities. Each name is indented to show how deep in the
`'#include'' stack it is.
`-P'
Inhibit generation of linemarkers in the output from the
preprocessor. This might be useful when running the preprocessor
on something that is not C code, and will be sent to a program
which might be confused by the linemarkers.
`-UNAME'
Cancel any previous definition of NAME, either built in or provided
with a `-D' option.

File: gfortran.info, Node: Error and Warning Options, Next: Debugging Options, Prev: Preprocessing Options, Up: Invoking GNU Fortran
2.4 Options to request or suppress errors and warnings
======================================================
Errors are diagnostic messages that report that the GNU Fortran compiler
cannot compile the relevant piece of source code. The compiler will
continue to process the program in an attempt to report further errors
to aid in debugging, but will not produce any compiled output.
Warnings are diagnostic messages that report constructions which are
not inherently erroneous but which are risky or suggest there is likely
to be a bug in the program. Unless `-Werror' is specified, they do not
prevent compilation of the program.
You can request many specific warnings with options beginning `-W',
for example `-Wimplicit' to request warnings on implicit declarations.
Each of these specific warning options also has a negative form
beginning `-Wno-' to turn off warnings; for example, `-Wno-implicit'.
This manual lists only one of the two forms, whichever is not the
default.
These options control the amount and kinds of errors and warnings
produced by GNU Fortran:
`-fmax-errors=N'
Limits the maximum number of error messages to N, at which point
GNU Fortran bails out rather than attempting to continue
processing the source code. If N is 0, there is no limit on the
number of error messages produced.
`-fsyntax-only'
Check the code for syntax errors, but don't actually compile it.
This will generate module files for each module present in the
code, but no other output file.
`-pedantic'
Issue warnings for uses of extensions to Fortran 95. `-pedantic'
also applies to C-language constructs where they occur in GNU
Fortran source files, such as use of `\e' in a character constant
within a directive like `#include'.
Valid Fortran 95 programs should compile properly with or without
this option. However, without this option, certain GNU extensions
and traditional Fortran features are supported as well. With this
option, many of them are rejected.
Some users try to use `-pedantic' to check programs for
conformance. They soon find that it does not do quite what they
want--it finds some nonstandard practices, but not all. However,
improvements to GNU Fortran in this area are welcome.
This should be used in conjunction with `-std=f95', `-std=f2003'
or `-std=f2008'.
`-pedantic-errors'
Like `-pedantic', except that errors are produced rather than
warnings.
`-Wall'
Enables commonly used warning options pertaining to usage that we
recommend avoiding and that we believe are easy to avoid. This
currently includes `-Waliasing', `-Wampersand', `-Wsurprising',
`-Wintrinsics-std', `-Wno-tabs', `-Wintrinsic-shadow' and
`-Wline-truncation'.
`-Waliasing'
Warn about possible aliasing of dummy arguments. Specifically, it
warns if the same actual argument is associated with a dummy
argument with `INTENT(IN)' and a dummy argument with `INTENT(OUT)'
in a call with an explicit interface.
The following example will trigger the warning.
interface
subroutine bar(a,b)
integer, intent(in) :: a
integer, intent(out) :: b
end subroutine
end interface
integer :: a
call bar(a,a)
`-Wampersand'
Warn about missing ampersand in continued character constants. The
warning is given with `-Wampersand', `-pedantic', `-std=f95',
`-std=f2003' and `-std=f2008'. Note: With no ampersand given in a
continued character constant, GNU Fortran assumes continuation at
the first non-comment, non-whitespace character after the ampersand
that initiated the continuation.
`-Warray-temporaries'
Warn about array temporaries generated by the compiler. The
information generated by this warning is sometimes useful in
optimization, in order to avoid such temporaries.
`-Wcharacter-truncation'
Warn when a character assignment will truncate the assigned string.
`-Wline-truncation'
Warn when a source code line will be truncated.
`-Wconversion'
Warn about implicit conversions between different types.
`-Wimplicit-interface'
Warn if a procedure is called without an explicit interface. Note
this only checks that an explicit interface is present. It does
not check that the declared interfaces are consistent across
program units.
`-Wimplicit-procedure'
Warn if a procedure is called that has neither an explicit
interface nor has been declared as `EXTERNAL'.
`-Wintrinsics-std'
Warn if `gfortran' finds a procedure named like an intrinsic not
available in the currently selected standard (with `-std') and
treats it as `EXTERNAL' procedure because of this.
`-fall-intrinsics' can be used to never trigger this behavior and
always link to the intrinsic regardless of the selected standard.
`-Wsurprising'
Produce a warning when "suspicious" code constructs are
encountered. While technically legal these usually indicate that
an error has been made.
This currently produces a warning under the following
circumstances:
* An INTEGER SELECT construct has a CASE that can never be
matched as its lower value is greater than its upper value.
* A LOGICAL SELECT construct has three CASE statements.
* A TRANSFER specifies a source that is shorter than the
destination.
* The type of a function result is declared more than once with
the same type. If `-pedantic' or standard-conforming mode is
enabled, this is an error.
* A `CHARACTER' variable is declared with negative length.
`-Wtabs'
By default, tabs are accepted as whitespace, but tabs are not
members of the Fortran Character Set. For continuation lines, a
tab followed by a digit between 1 and 9 is supported. `-Wno-tabs'
will cause a warning to be issued if a tab is encountered. Note,
`-Wno-tabs' is active for `-pedantic', `-std=f95', `-std=f2003',
`-std=f2008' and `-Wall'.
`-Wunderflow'
Produce a warning when numerical constant expressions are
encountered, which yield an UNDERFLOW during compilation.
`-Wintrinsic-shadow'
Warn if a user-defined procedure or module procedure has the same
name as an intrinsic; in this case, an explicit interface or
`EXTERNAL' or `INTRINSIC' declaration might be needed to get calls
later resolved to the desired intrinsic/procedure.
`-Wunused-parameter'
Contrary to `gcc''s meaning of `-Wunused-parameter', `gfortran''s
implementation of this option does not warn about unused dummy
arguments, but about unused `PARAMETER' values.
`-Wunused-parameter' is not included in `-Wall' but is implied by
`-Wall -Wextra'.
`-Walign-commons'
By default, `gfortran' warns about any occasion of variables being
padded for proper alignment inside a COMMON block. This warning
can be turned off via `-Wno-align-commons'. See also
`-falign-commons'.
`-Werror'
Turns all warnings into errors.
*Note Options to Request or Suppress Errors and Warnings: (gcc)Error
and Warning Options, for information on more options offered by the GBE
shared by `gfortran', `gcc' and other GNU compilers.
Some of these have no effect when compiling programs written in
Fortran.

File: gfortran.info, Node: Debugging Options, Next: Directory Options, Prev: Error and Warning Options, Up: Invoking GNU Fortran
2.5 Options for debugging your program or GNU Fortran
=====================================================
GNU Fortran has various special options that are used for debugging
either your program or the GNU Fortran compiler.
`-fdump-parse-tree'
Output the internal parse tree before starting code generation.
Only really useful for debugging the GNU Fortran compiler itself.
`-ffpe-trap=LIST'
Specify a list of IEEE exceptions when a Floating Point Exception
(FPE) should be raised. On most systems, this will result in a
SIGFPE signal being sent and the program being interrupted,
producing a core file useful for debugging. LIST is a (possibly
empty) comma-separated list of the following IEEE exceptions:
`invalid' (invalid floating point operation, such as
`SQRT(-1.0)'), `zero' (division by zero), `overflow' (overflow in
a floating point operation), `underflow' (underflow in a floating
point operation), `precision' (loss of precision during operation)
and `denormal' (operation produced a denormal value).
Some of the routines in the Fortran runtime library, like
`CPU_TIME', are likely to trigger floating point exceptions when
`ffpe-trap=precision' is used. For this reason, the use of
`ffpe-trap=precision' is not recommended.
`-fbacktrace'
Specify that, when a runtime error is encountered or a deadly
signal is emitted (segmentation fault, illegal instruction, bus
error or floating-point exception), the Fortran runtime library
should output a backtrace of the error. This option only has
influence for compilation of the Fortran main program.
`-fdump-core'
Request that a core-dump file is written to disk when a runtime
error is encountered on systems that support core dumps. This
option is only effective for the compilation of the Fortran main
program.
*Note Options for Debugging Your Program or GCC: (gcc)Debugging
Options, for more information on debugging options.

File: gfortran.info, Node: Directory Options, Next: Link Options, Prev: Debugging Options, Up: Invoking GNU Fortran
2.6 Options for directory search
================================
These options affect how GNU Fortran searches for files specified by
the `INCLUDE' directive and where it searches for previously compiled
modules.
It also affects the search paths used by `cpp' when used to
preprocess Fortran source.
`-IDIR'
These affect interpretation of the `INCLUDE' directive (as well as
of the `#include' directive of the `cpp' preprocessor).
Also note that the general behavior of `-I' and `INCLUDE' is
pretty much the same as of `-I' with `#include' in the `cpp'
preprocessor, with regard to looking for `header.gcc' files and
other such things.
This path is also used to search for `.mod' files when previously
compiled modules are required by a `USE' statement.
*Note Options for Directory Search: (gcc)Directory Options, for
information on the `-I' option.
`-JDIR'
This option specifies where to put `.mod' files for compiled
modules. It is also added to the list of directories to searched
by an `USE' statement.
The default is the current directory.
`-fintrinsic-modules-path DIR'
This option specifies the location of pre-compiled intrinsic
modules, if they are not in the default location expected by the
compiler.

File: gfortran.info, Node: Link Options, Next: Runtime Options, Prev: Directory Options, Up: Invoking GNU Fortran
2.7 Influencing the linking step
================================
These options come into play when the compiler links object files into
an executable output file. They are meaningless if the compiler is not
doing a link step.
`-static-libgfortran'
On systems that provide `libgfortran' as a shared and a static
library, this option forces the use of the static version. If no
shared version of `libgfortran' was built when the compiler was
configured, this option has no effect.

File: gfortran.info, Node: Runtime Options, Next: Code Gen Options, Prev: Link Options, Up: Invoking GNU Fortran
2.8 Influencing runtime behavior
================================
These options affect the runtime behavior of programs compiled with GNU
Fortran.
`-fconvert=CONVERSION'
Specify the representation of data for unformatted files. Valid
values for conversion are: `native', the default; `swap', swap
between big- and little-endian; `big-endian', use big-endian
representation for unformatted files; `little-endian', use
little-endian representation for unformatted files.
_This option has an effect only when used in the main program.
The `CONVERT' specifier and the GFORTRAN_CONVERT_UNIT environment
variable override the default specified by `-fconvert'._
`-fno-range-check'
Disable range checking of input values during integer `READ'
operations. For example, GNU Fortran will give an error if an
input value is outside of the relevant range of
[`-HUGE()':`HUGE()']. In other words, with `INTEGER (kind=4) :: i'
, attempting to read -2147483648 will give an error unless
`-fno-range-check' is given.
`-frecord-marker=LENGTH'
Specify the length of record markers for unformatted files. Valid
values for LENGTH are 4 and 8. Default is 4. _This is different
from previous versions of `gfortran'_, which specified a default
record marker length of 8 on most systems. If you want to read or
write files compatible with earlier versions of `gfortran', use
`-frecord-marker=8'.
`-fmax-subrecord-length=LENGTH'
Specify the maximum length for a subrecord. The maximum permitted
value for length is 2147483639, which is also the default. Only
really useful for use by the gfortran testsuite.
`-fsign-zero'
When enabled, floating point numbers of value zero with the sign
bit set are written as negative number in formatted output and
treated as negative in the `SIGN' intrinsic. `fno-sign-zero' does
not print the negative sign of zero values and regards zero as
positive number in the `SIGN' intrinsic for compatibility with F77.
Default behavior is to show the negative sign.

File: gfortran.info, Node: Code Gen Options, Next: Environment Variables, Prev: Runtime Options, Up: Invoking GNU Fortran
2.9 Options for code generation conventions
===========================================
These machine-independent options control the interface conventions
used in code generation.
Most of them have both positive and negative forms; the negative form
of `-ffoo' would be `-fno-foo'. In the table below, only one of the
forms is listed--the one which is not the default. You can figure out
the other form by either removing `no-' or adding it.
`-fno-automatic'
Treat each program unit (except those marked as RECURSIVE) as if
the `SAVE' statement were specified for every local variable and
array referenced in it. Does not affect common blocks. (Some
Fortran compilers provide this option under the name `-static' or
`-save'.) The default, which is `-fautomatic', uses the stack for
local variables smaller than the value given by
`-fmax-stack-var-size'. Use the option `-frecursive' to use no
static memory.
`-ff2c'
Generate code designed to be compatible with code generated by
`g77' and `f2c'.
The calling conventions used by `g77' (originally implemented in
`f2c') require functions that return type default `REAL' to
actually return the C type `double', and functions that return
type `COMPLEX' to return the values via an extra argument in the
calling sequence that points to where to store the return value.
Under the default GNU calling conventions, such functions simply
return their results as they would in GNU C--default `REAL'
functions return the C type `float', and `COMPLEX' functions
return the GNU C type `complex'. Additionally, this option
implies the `-fsecond-underscore' option, unless
`-fno-second-underscore' is explicitly requested.
This does not affect the generation of code that interfaces with
the `libgfortran' library.
_Caution:_ It is not a good idea to mix Fortran code compiled with
`-ff2c' with code compiled with the default `-fno-f2c' calling
conventions as, calling `COMPLEX' or default `REAL' functions
between program parts which were compiled with different calling
conventions will break at execution time.
_Caution:_ This will break code which passes intrinsic functions
of type default `REAL' or `COMPLEX' as actual arguments, as the
library implementations use the `-fno-f2c' calling conventions.
`-fno-underscoring'
Do not transform names of entities specified in the Fortran source
file by appending underscores to them.
With `-funderscoring' in effect, GNU Fortran appends one
underscore to external names with no underscores. This is done to
ensure compatibility with code produced by many UNIX Fortran
compilers.
_Caution_: The default behavior of GNU Fortran is incompatible
with `f2c' and `g77', please use the `-ff2c' option if you want
object files compiled with GNU Fortran to be compatible with
object code created with these tools.
Use of `-fno-underscoring' is not recommended unless you are
experimenting with issues such as integration of GNU Fortran into
existing system environments (vis-a`-vis existing libraries, tools,
and so on).
For example, with `-funderscoring', and assuming other defaults
like `-fcase-lower' and that `j()' and `max_count()' are external
functions while `my_var' and `lvar' are local variables, a
statement like
I = J() + MAX_COUNT (MY_VAR, LVAR)
is implemented as something akin to:
i = j_() + max_count__(&my_var__, &lvar);
With `-fno-underscoring', the same statement is implemented as:
i = j() + max_count(&my_var, &lvar);
Use of `-fno-underscoring' allows direct specification of
user-defined names while debugging and when interfacing GNU Fortran
code with other languages.
Note that just because the names match does _not_ mean that the
interface implemented by GNU Fortran for an external name matches
the interface implemented by some other language for that same
name. That is, getting code produced by GNU Fortran to link to
code produced by some other compiler using this or any other
method can be only a small part of the overall solution--getting
the code generated by both compilers to agree on issues other than
naming can require significant effort, and, unlike naming
disagreements, linkers normally cannot detect disagreements in
these other areas.
Also, note that with `-fno-underscoring', the lack of appended
underscores introduces the very real possibility that a
user-defined external name will conflict with a name in a system
library, which could make finding unresolved-reference bugs quite
difficult in some cases--they might occur at program run time, and
show up only as buggy behavior at run time.
In future versions of GNU Fortran we hope to improve naming and
linking issues so that debugging always involves using the names
as they appear in the source, even if the names as seen by the
linker are mangled to prevent accidental linking between
procedures with incompatible interfaces.
`-fwhole-file'
By default, GNU Fortran parses, resolves and translates each
procedure in a file separately. Using this option modifies this
such that the whole file is parsed and placed in a single
front-end tree. During resolution, in addition to all the usual
checks and fixups, references to external procedures that are in
the same file effect resolution of that procedure, if not already
done, and a check of the interfaces. The dependences are resolved
by changing the order in which the file is translated into the
backend tree. Thus, a procedure that is referenced is translated
before the reference and the duplication of backend tree
declarations eliminated.
`-fsecond-underscore'
By default, GNU Fortran appends an underscore to external names.
If this option is used GNU Fortran appends two underscores to
names with underscores and one underscore to external names with
no underscores. GNU Fortran also appends two underscores to
internal names with underscores to avoid naming collisions with
external names.
This option has no effect if `-fno-underscoring' is in effect. It
is implied by the `-ff2c' option.
Otherwise, with this option, an external name such as `MAX_COUNT'
is implemented as a reference to the link-time external symbol
`max_count__', instead of `max_count_'. This is required for
compatibility with `g77' and `f2c', and is implied by use of the
`-ff2c' option.
`-fcheck=<KEYWORD>'
Enable the generation of run-time checks; the argument shall be a
comma-delimited list of the following keywords.
`all'
Enable all run-time test of `-fcheck'.
`array-temps'
Warns at run time when for passing an actual argument a
temporary array had to be generated. The information
generated by this warning is sometimes useful in
optimization, in order to avoid such temporaries.
Note: The warning is only printed once per location.
`bounds'
Enable generation of run-time checks for array subscripts and
against the declared minimum and maximum values. It also
checks array indices for assumed and deferred shape arrays
against the actual allocated bounds and ensures that all
string lengths are equal for character array constructors
without an explicit typespec.
Some checks require that `-fcheck=bounds' is set for the
compilation of the main program.
Note: In the future this may also include other forms of
checking, e.g., checking substring references.
`do'
Enable generation of run-time checks for invalid modification
of loop iteration variables.
`mem'
Enable generation of run-time checks for memory allocation.
Note: This option does not affect explicit allocations using
the `ALLOCATE' statement, which will be always checked.
`pointer'
Enable generation of run-time checks for pointers and
allocatables.
`recursion'
Enable generation of run-time checks for recursively called
subroutines and functions which are not marked as recursive.
See also `-frecursive'. Note: This check does not work for
OpenMP programs and is disabled if used together with
`-frecursive' and `-fopenmp'.
`-fbounds-check'
Deprecated alias for `-fcheck=bounds'.
`-fcheck-array-temporaries'
Deprecated alias for `-fcheck=array-temps'.
`-fmax-array-constructor=N'
This option can be used to increase the upper limit permitted in
array constructors. The code below requires this option to expand
the array at compile time.
`program test'
`implicit none'
`integer j'
`integer, parameter :: n = 100000'
`integer, parameter :: i(n) = (/ (2*j, j = 1, n) /)'
`print '(10(I0,1X))', i'
`end program test'
_Caution: This option can lead to long compile times and
excessively large object files._
The default value for N is 65535.
`-fmax-stack-var-size=N'
This option specifies the size in bytes of the largest array that
will be put on the stack; if the size is exceeded static memory is
used (except in procedures marked as RECURSIVE). Use the option
`-frecursive' to allow for recursive procedures which do not have
a RECURSIVE attribute or for parallel programs. Use
`-fno-automatic' to never use the stack.
This option currently only affects local arrays declared with
constant bounds, and may not apply to all character variables.
Future versions of GNU Fortran may improve this behavior.
The default value for N is 32768.
`-fpack-derived'
This option tells GNU Fortran to pack derived type members as
closely as possible. Code compiled with this option is likely to
be incompatible with code compiled without this option, and may
execute slower.
`-frepack-arrays'
In some circumstances GNU Fortran may pass assumed shape array
sections via a descriptor describing a noncontiguous area of
memory. This option adds code to the function prologue to repack
the data into a contiguous block at runtime.
This should result in faster accesses to the array. However it
can introduce significant overhead to the function call,
especially when the passed data is noncontiguous.
`-fshort-enums'
This option is provided for interoperability with C code that was
compiled with the `-fshort-enums' option. It will make GNU
Fortran choose the smallest `INTEGER' kind a given enumerator set
will fit in, and give all its enumerators this kind.
`-fexternal-blas'
This option will make `gfortran' generate calls to BLAS functions
for some matrix operations like `MATMUL', instead of using our own
algorithms, if the size of the matrices involved is larger than a
given limit (see `-fblas-matmul-limit'). This may be profitable
if an optimized vendor BLAS library is available. The BLAS
library will have to be specified at link time.
`-fblas-matmul-limit=N'
Only significant when `-fexternal-blas' is in effect. Matrix
multiplication of matrices with size larger than (or equal to) N
will be performed by calls to BLAS functions, while others will be
handled by `gfortran' internal algorithms. If the matrices
involved are not square, the size comparison is performed using the
geometric mean of the dimensions of the argument and result
matrices.
The default value for N is 30.
`-frecursive'
Allow indirect recursion by forcing all local arrays to be
allocated on the stack. This flag cannot be used together with
`-fmax-stack-var-size=' or `-fno-automatic'.
`-finit-local-zero'
`-finit-integer=N'
`-finit-real=<ZERO|INF|-INF|NAN|SNAN>'
`-finit-logical=<TRUE|FALSE>'
`-finit-character=N'
The `-finit-local-zero' option instructs the compiler to
initialize local `INTEGER', `REAL', and `COMPLEX' variables to
zero, `LOGICAL' variables to false, and `CHARACTER' variables to a
string of null bytes. Finer-grained initialization options are
provided by the `-finit-integer=N',
`-finit-real=<ZERO|INF|-INF|NAN|SNAN>' (which also initializes the
real and imaginary parts of local `COMPLEX' variables),
`-finit-logical=<TRUE|FALSE>', and `-finit-character=N' (where N
is an ASCII character value) options. These options do not
initialize components of derived type variables, nor do they
initialize variables that appear in an `EQUIVALENCE' statement.
(This limitation may be removed in future releases).
Note that the `-finit-real=nan' option initializes `REAL' and
`COMPLEX' variables with a quiet NaN. For a signalling NaN use
`-finit-real=snan'; note, however, that compile-time optimizations
may convert them into quiet NaN and that trapping needs to be
enabled (e.g. via `-ffpe-trap').
`-falign-commons'
By default, `gfortran' enforces proper alignment of all variables
in a COMMON block by padding them as needed. On certain platforms
this is mandatory, on others it increases performance. If a COMMON
block is not declared with consistent data types everywhere, this
padding can cause trouble, and `-fno-align-commons ' can be used
to disable automatic alignment. The same form of this option
should be used for all files that share a COMMON block. To avoid
potential alignment issues in COMMON blocks, it is recommended to
order objects from largests to smallest.
`-fno-protect-parens'
By default the parentheses in expression are honored for all
optimization levels such that the compiler does not do any
re-association. Using `-fno-protect-parens' allows the compiler to
reorder REAL and COMPLEX expressions to produce faster code. Note
that for the re-association optimization `-fno-signed-zeros' and
`-fno-trapping-math' need to be in effect.
*Note Options for Code Generation Conventions: (gcc)Code Gen
Options, for information on more options offered by the GBE shared by
`gfortran', `gcc', and other GNU compilers.

File: gfortran.info, Node: Environment Variables, Prev: Code Gen Options, Up: Invoking GNU Fortran
2.10 Environment variables affecting `gfortran'
===============================================
The `gfortran' compiler currently does not make use of any environment
variables to control its operation above and beyond those that affect
the operation of `gcc'.
*Note Environment Variables Affecting GCC: (gcc)Environment
Variables, for information on environment variables.
*Note Runtime::, for environment variables that affect the run-time
behavior of programs compiled with GNU Fortran.

File: gfortran.info, Node: Runtime, Next: Fortran 2003 and 2008 status, Prev: Invoking GNU Fortran, Up: Top
3 Runtime: Influencing runtime behavior with environment variables
*******************************************************************
The behavior of the `gfortran' can be influenced by environment
variables.
Malformed environment variables are silently ignored.
* Menu:
* GFORTRAN_STDIN_UNIT:: Unit number for standard input
* GFORTRAN_STDOUT_UNIT:: Unit number for standard output
* GFORTRAN_STDERR_UNIT:: Unit number for standard error
* GFORTRAN_USE_STDERR:: Send library output to standard error
* GFORTRAN_TMPDIR:: Directory for scratch files
* GFORTRAN_UNBUFFERED_ALL:: Don't buffer I/O for all units.
* GFORTRAN_UNBUFFERED_PRECONNECTED:: Don't buffer I/O for preconnected units.
* GFORTRAN_SHOW_LOCUS:: Show location for runtime errors
* GFORTRAN_OPTIONAL_PLUS:: Print leading + where permitted
* GFORTRAN_DEFAULT_RECL:: Default record length for new files
* GFORTRAN_LIST_SEPARATOR:: Separator for list output
* GFORTRAN_CONVERT_UNIT:: Set endianness for unformatted I/O
* GFORTRAN_ERROR_DUMPCORE:: Dump core on run-time errors
* GFORTRAN_ERROR_BACKTRACE:: Show backtrace on run-time errors

File: gfortran.info, Node: GFORTRAN_STDIN_UNIT, Next: GFORTRAN_STDOUT_UNIT, Up: Runtime
3.1 `GFORTRAN_STDIN_UNIT'--Unit number for standard input
=========================================================
This environment variable can be used to select the unit number
preconnected to standard input. This must be a positive integer. The
default value is 5.

File: gfortran.info, Node: GFORTRAN_STDOUT_UNIT, Next: GFORTRAN_STDERR_UNIT, Prev: GFORTRAN_STDIN_UNIT, Up: Runtime
3.2 `GFORTRAN_STDOUT_UNIT'--Unit number for standard output
===========================================================
This environment variable can be used to select the unit number
preconnected to standard output. This must be a positive integer. The
default value is 6.

File: gfortran.info, Node: GFORTRAN_STDERR_UNIT, Next: GFORTRAN_USE_STDERR, Prev: GFORTRAN_STDOUT_UNIT, Up: Runtime
3.3 `GFORTRAN_STDERR_UNIT'--Unit number for standard error
==========================================================
This environment variable can be used to select the unit number
preconnected to standard error. This must be a positive integer. The
default value is 0.

File: gfortran.info, Node: GFORTRAN_USE_STDERR, Next: GFORTRAN_TMPDIR, Prev: GFORTRAN_STDERR_UNIT, Up: Runtime
3.4 `GFORTRAN_USE_STDERR'--Send library output to standard error
================================================================
This environment variable controls where library output is sent. If
the first letter is `y', `Y' or `1', standard error is used. If the
first letter is `n', `N' or `0', standard output is used.

File: gfortran.info, Node: GFORTRAN_TMPDIR, Next: GFORTRAN_UNBUFFERED_ALL, Prev: GFORTRAN_USE_STDERR, Up: Runtime
3.5 `GFORTRAN_TMPDIR'--Directory for scratch files
==================================================
This environment variable controls where scratch files are created. If
this environment variable is missing, GNU Fortran searches for the
environment variable `TMP'. If this is also missing, the default is
`/tmp'.

File: gfortran.info, Node: GFORTRAN_UNBUFFERED_ALL, Next: GFORTRAN_UNBUFFERED_PRECONNECTED, Prev: GFORTRAN_TMPDIR, Up: Runtime
3.6 `GFORTRAN_UNBUFFERED_ALL'--Don't buffer I/O on all units
============================================================
This environment variable controls whether all I/O is unbuffered. If
the first letter is `y', `Y' or `1', all I/O is unbuffered. This will
slow down small sequential reads and writes. If the first letter is
`n', `N' or `0', I/O is buffered. This is the default.

File: gfortran.info, Node: GFORTRAN_UNBUFFERED_PRECONNECTED, Next: GFORTRAN_SHOW_LOCUS, Prev: GFORTRAN_UNBUFFERED_ALL, Up: Runtime
3.7 `GFORTRAN_UNBUFFERED_PRECONNECTED'--Don't buffer I/O on preconnected units
==============================================================================
The environment variable named `GFORTRAN_UNBUFFERED_PRECONNECTED'
controls whether I/O on a preconnected unit (i.e. STDOUT or STDERR) is
unbuffered. If the first letter is `y', `Y' or `1', I/O is unbuffered.
This will slow down small sequential reads and writes. If the first
letter is `n', `N' or `0', I/O is buffered. This is the default.

File: gfortran.info, Node: GFORTRAN_SHOW_LOCUS, Next: GFORTRAN_OPTIONAL_PLUS, Prev: GFORTRAN_UNBUFFERED_PRECONNECTED, Up: Runtime
3.8 `GFORTRAN_SHOW_LOCUS'--Show location for runtime errors
===========================================================
If the first letter is `y', `Y' or `1', filename and line numbers for
runtime errors are printed. If the first letter is `n', `N' or `0',
don't print filename and line numbers for runtime errors. The default
is to print the location.

File: gfortran.info, Node: GFORTRAN_OPTIONAL_PLUS, Next: GFORTRAN_DEFAULT_RECL, Prev: GFORTRAN_SHOW_LOCUS, Up: Runtime
3.9 `GFORTRAN_OPTIONAL_PLUS'--Print leading + where permitted
=============================================================
If the first letter is `y', `Y' or `1', a plus sign is printed where
permitted by the Fortran standard. If the first letter is `n', `N' or
`0', a plus sign is not printed in most cases. Default is not to print
plus signs.

File: gfortran.info, Node: GFORTRAN_DEFAULT_RECL, Next: GFORTRAN_LIST_SEPARATOR, Prev: GFORTRAN_OPTIONAL_PLUS, Up: Runtime
3.10 `GFORTRAN_DEFAULT_RECL'--Default record length for new files
=================================================================
This environment variable specifies the default record length, in
bytes, for files which are opened without a `RECL' tag in the `OPEN'
statement. This must be a positive integer. The default value is
1073741824 bytes (1 GB).

File: gfortran.info, Node: GFORTRAN_LIST_SEPARATOR, Next: GFORTRAN_CONVERT_UNIT, Prev: GFORTRAN_DEFAULT_RECL, Up: Runtime
3.11 `GFORTRAN_LIST_SEPARATOR'--Separator for list output
=========================================================
This environment variable specifies the separator when writing
list-directed output. It may contain any number of spaces and at most
one comma. If you specify this on the command line, be sure to quote
spaces, as in
$ GFORTRAN_LIST_SEPARATOR=' , ' ./a.out
when `a.out' is the compiled Fortran program that you want to run.
Default is a single space.

File: gfortran.info, Node: GFORTRAN_CONVERT_UNIT, Next: GFORTRAN_ERROR_DUMPCORE, Prev: GFORTRAN_LIST_SEPARATOR, Up: Runtime
3.12 `GFORTRAN_CONVERT_UNIT'--Set endianness for unformatted I/O
================================================================
By setting the `GFORTRAN_CONVERT_UNIT' variable, it is possible to
change the representation of data for unformatted files. The syntax
for the `GFORTRAN_CONVERT_UNIT' variable is:
GFORTRAN_CONVERT_UNIT: mode | mode ';' exception | exception ;
mode: 'native' | 'swap' | 'big_endian' | 'little_endian' ;
exception: mode ':' unit_list | unit_list ;
unit_list: unit_spec | unit_list unit_spec ;
unit_spec: INTEGER | INTEGER '-' INTEGER ;
The variable consists of an optional default mode, followed by a
list of optional exceptions, which are separated by semicolons from the
preceding default and each other. Each exception consists of a format
and a comma-separated list of units. Valid values for the modes are
the same as for the `CONVERT' specifier:
`NATIVE' Use the native format. This is the default.
`SWAP' Swap between little- and big-endian.
`LITTLE_ENDIAN' Use the little-endian format for unformatted files.
`BIG_ENDIAN' Use the big-endian format for unformatted files.
A missing mode for an exception is taken to mean `BIG_ENDIAN'.
Examples of values for `GFORTRAN_CONVERT_UNIT' are:
`'big_endian'' Do all unformatted I/O in big_endian mode.
`'little_endian;native:10-20,25'' Do all unformatted I/O in
little_endian mode, except for units 10 to 20 and 25, which are in
native format.
`'10-20'' Units 10 to 20 are big-endian, the rest is native.
Setting the environment variables should be done on the command line
or via the `export' command for `sh'-compatible shells and via `setenv'
for `csh'-compatible shells.
Example for `sh':
$ gfortran foo.f90
$ GFORTRAN_CONVERT_UNIT='big_endian;native:10-20' ./a.out
Example code for `csh':
% gfortran foo.f90
% setenv GFORTRAN_CONVERT_UNIT 'big_endian;native:10-20'
% ./a.out
Using anything but the native representation for unformatted data
carries a significant speed overhead. If speed in this area matters to
you, it is best if you use this only for data that needs to be portable.
*Note CONVERT specifier::, for an alternative way to specify the
data representation for unformatted files. *Note Runtime Options::, for
setting a default data representation for the whole program. The
`CONVERT' specifier overrides the `-fconvert' compile options.
_Note that the values specified via the GFORTRAN_CONVERT_UNIT
environment variable will override the CONVERT specifier in the open
statement_. This is to give control over data formats to users who do
not have the source code of their program available.

File: gfortran.info, Node: GFORTRAN_ERROR_DUMPCORE, Next: GFORTRAN_ERROR_BACKTRACE, Prev: GFORTRAN_CONVERT_UNIT, Up: Runtime
3.13 `GFORTRAN_ERROR_DUMPCORE'--Dump core on run-time errors
============================================================
If the `GFORTRAN_ERROR_DUMPCORE' variable is set to `y', `Y' or `1'
(only the first letter is relevant) then library run-time errors cause
core dumps. To disable the core dumps, set the variable to `n', `N',
`0'. Default is not to core dump unless the `-fdump-core' compile option
was used.

File: gfortran.info, Node: GFORTRAN_ERROR_BACKTRACE, Prev: GFORTRAN_ERROR_DUMPCORE, Up: Runtime
3.14 `GFORTRAN_ERROR_BACKTRACE'--Show backtrace on run-time errors
==================================================================
If the `GFORTRAN_ERROR_BACKTRACE' variable is set to `y', `Y' or `1'
(only the first letter is relevant) then a backtrace is printed when a
run-time error occurs. To disable the backtracing, set the variable to
`n', `N', `0'. Default is not to print a backtrace unless the
`-fbacktrace' compile option was used.

File: gfortran.info, Node: Fortran 2003 and 2008 status, Next: Compiler Characteristics, Prev: Runtime, Up: Top
4 Fortran 2003 and 2008 Status
******************************
* Menu:
* Fortran 2003 status::
* Fortran 2008 status::

File: gfortran.info, Node: Fortran 2003 status, Next: Fortran 2008 status, Up: Fortran 2003 and 2008 status
4.1 Fortran 2003 status
=======================
GNU Fortran supports several Fortran 2003 features; an incomplete list
can be found below. See also the wiki page
(http://gcc.gnu.org/wiki/Fortran2003) about Fortran 2003.
* Intrinsics `command_argument_count', `get_command',
`get_command_argument', `get_environment_variable', and
`move_alloc'.
* Array constructors using square brackets. That is, `[...]' rather
than `(/.../)'. Type-specification for array constructors like
`(/ some-type :: ... /)'.
* `FLUSH' statement.
* `IOMSG=' specifier for I/O statements.
* Support for the declaration of enumeration constants via the
`ENUM' and `ENUMERATOR' statements. Interoperability with `gcc'
is guaranteed also for the case where the `-fshort-enums' command
line option is given.
* TR 15581:
* `ALLOCATABLE' dummy arguments.
* `ALLOCATABLE' function results
* `ALLOCATABLE' components of derived types
* The `ERRMSG=' tag is now supported in `ALLOCATE' and `DEALLOCATE'
statements. The `SOURCE=' tag is supported in an `ALLOCATE'
statement. An _intrinsic-type-spec_ can be used as the
_type-spec_ in an `ALLOCATE' statement; while the use of a
_derived-type-name_ is currently unsupported.
* The `OPEN' statement supports the `ACCESS='STREAM'' specifier,
allowing I/O without any record structure.
* Namelist input/output for internal files.
* The `PROTECTED' statement and attribute.
* The `VALUE' statement and attribute.
* The `VOLATILE' statement and attribute.
* The `IMPORT' statement, allowing to import host-associated derived
types.
* `USE' statement with `INTRINSIC' and `NON_INTRINSIC' attribute;
supported intrinsic modules: `ISO_FORTRAN_ENV', `OMP_LIB' and
`OMP_LIB_KINDS'.
* Renaming of operators in the `USE' statement.
* Interoperability with C (ISO C Bindings)
* BOZ as argument of `INT', `REAL', `DBLE' and `CMPLX'.
* Type-bound procedures with `PROCEDURE' or `GENERIC', and operators
bound to a derived-type.
* Extension of derived-types (the `EXTENDS(...)' syntax).
* `ABSTRACT' derived-types and declaring procedure bindings
`DEFERRED'.

File: gfortran.info, Node: Fortran 2008 status, Prev: Fortran 2003 status, Up: Fortran 2003 and 2008 status
4.2 Fortran 2008 status
=======================
The next version of the Fortran standard after Fortran 2003 is currently
being worked on by the Working Group 5 of Sub-Committee 22 of the Joint
Technical Committee 1 of the International Organization for
Standardization (ISO) and the International Electrotechnical Commission
(IEC). This group is known as WG5 (http://www.nag.co.uk/sc22wg5/). The
next revision of the Fortran standard is informally referred to as
Fortran 2008, reflecting its planned release year. The GNU Fortran
compiler has support for some of the new features in Fortran 2008. This
support is based on the latest draft, available from
`http://www.nag.co.uk/sc22wg5/'. However, as the final standard may
differ from the drafts, no guarantee of backward compatibility can be
made and you should only use it for experimental purposes.
The wiki (http://gcc.gnu.org/wiki/Fortran2008Status) has some
information about the current Fortran 2008 implementation status.

File: gfortran.info, Node: Compiler Characteristics, Next: Mixed-Language Programming, Prev: Fortran 2003 and 2008 status, Up: Top
5 Compiler Characteristics
**************************
This chapter describes certain characteristics of the GNU Fortran
compiler, that are not specified by the Fortran standard, but which
might in some way or another become visible to the programmer.
* Menu:
* KIND Type Parameters::
* Internal representation of LOGICAL variables::

File: gfortran.info, Node: KIND Type Parameters, Next: Internal representation of LOGICAL variables, Up: Compiler Characteristics
5.1 KIND Type Parameters
========================
The `KIND' type parameters supported by GNU Fortran for the primitive
data types are:
`INTEGER'
1, 2, 4, 8*, 16*, default: 4 (1)
`LOGICAL'
1, 2, 4, 8*, 16*, default: 4 (1)
`REAL'
4, 8, 10**, 16**, default: 4 (2)
`COMPLEX'
4, 8, 10**, 16**, default: 4 (2)
`CHARACTER'
1, 4, default: 1
* = not available on all systems
** = not available on all systems; additionally 10 and 16 are never
available at the same time
(1) Unless -fdefault-integer-8 is used
(2) Unless -fdefault-real-8 is used
The `KIND' value matches the storage size in bytes, except for
`COMPLEX' where the storage size is twice as much (or both real and
imaginary part are a real value of the given size). It is recommended
to use the `SELECT_*_KIND' intrinsics instead of the concrete values.

File: gfortran.info, Node: Internal representation of LOGICAL variables, Prev: KIND Type Parameters, Up: Compiler Characteristics
5.2 Internal representation of LOGICAL variables
================================================
The Fortran standard does not specify how variables of `LOGICAL' type
are represented, beyond requiring that `LOGICAL' variables of default
kind have the same storage size as default `INTEGER' and `REAL'
variables. The GNU Fortran internal representation is as follows.
A `LOGICAL(KIND=N)' variable is represented as an `INTEGER(KIND=N)'
variable, however, with only two permissible values: `1' for `.TRUE.'
and `0' for `.FALSE.'. Any other integer value results in undefined
behavior.
Note that for mixed-language programming using the `ISO_C_BINDING'
feature, there is a `C_BOOL' kind that can be used to create
`LOGICAL(KIND=C_BOOL)' variables which are interoperable with the C99
_Bool type. The C99 _Bool type has an internal representation
described in the C99 standard, which is identical to the above
description, i.e. with 1 for true and 0 for false being the only
permissible values. Thus the internal representation of `LOGICAL'
variables in GNU Fortran is identical to C99 _Bool, except for a
possible difference in storage size depending on the kind.

File: gfortran.info, Node: Extensions, Next: Intrinsic Procedures, Prev: Mixed-Language Programming, Up: Top
6 Extensions
************
The two sections below detail the extensions to standard Fortran that
are implemented in GNU Fortran, as well as some of the popular or
historically important extensions that are not (or not yet) implemented.
For the latter case, we explain the alternatives available to GNU
Fortran users, including replacement by standard-conforming code or GNU
extensions.
* Menu:
* Extensions implemented in GNU Fortran::
* Extensions not implemented in GNU Fortran::

File: gfortran.info, Node: Extensions implemented in GNU Fortran, Next: Extensions not implemented in GNU Fortran, Up: Extensions
6.1 Extensions implemented in GNU Fortran
=========================================
GNU Fortran implements a number of extensions over standard Fortran.
This chapter contains information on their syntax and meaning. There
are currently two categories of GNU Fortran extensions, those that
provide functionality beyond that provided by any standard, and those
that are supported by GNU Fortran purely for backward compatibility
with legacy compilers. By default, `-std=gnu' allows the compiler to
accept both types of extensions, but to warn about the use of the
latter. Specifying either `-std=f95', `-std=f2003' or `-std=f2008'
disables both types of extensions, and `-std=legacy' allows both
without warning.
* Menu:
* Old-style kind specifications::
* Old-style variable initialization::
* Extensions to namelist::
* X format descriptor without count field::
* Commas in FORMAT specifications::
* Missing period in FORMAT specifications::
* I/O item lists::
* BOZ literal constants::
* Real array indices::
* Unary operators::
* Implicitly convert LOGICAL and INTEGER values::
* Hollerith constants support::
* Cray pointers::
* CONVERT specifier::
* OpenMP::
* Argument list functions::

File: gfortran.info, Node: Old-style kind specifications, Next: Old-style variable initialization, Up: Extensions implemented in GNU Fortran
6.1.1 Old-style kind specifications
-----------------------------------
GNU Fortran allows old-style kind specifications in declarations. These
look like:
TYPESPEC*size x,y,z
where `TYPESPEC' is a basic type (`INTEGER', `REAL', etc.), and
where `size' is a byte count corresponding to the storage size of a
valid kind for that type. (For `COMPLEX' variables, `size' is the
total size of the real and imaginary parts.) The statement then
declares `x', `y' and `z' to be of type `TYPESPEC' with the appropriate
kind. This is equivalent to the standard-conforming declaration
TYPESPEC(k) x,y,z
where `k' is the kind parameter suitable for the intended precision.
As kind parameters are implementation-dependent, use the `KIND',
`SELECTED_INT_KIND' and `SELECTED_REAL_KIND' intrinsics to retrieve the
correct value, for instance `REAL*8 x' can be replaced by:
INTEGER, PARAMETER :: dbl = KIND(1.0d0)
REAL(KIND=dbl) :: x

File: gfortran.info, Node: Old-style variable initialization, Next: Extensions to namelist, Prev: Old-style kind specifications, Up: Extensions implemented in GNU Fortran
6.1.2 Old-style variable initialization
---------------------------------------
GNU Fortran allows old-style initialization of variables of the form:
INTEGER i/1/,j/2/
REAL x(2,2) /3*0.,1./
The syntax for the initializers is as for the `DATA' statement, but
unlike in a `DATA' statement, an initializer only applies to the
variable immediately preceding the initialization. In other words,
something like `INTEGER I,J/2,3/' is not valid. This style of
initialization is only allowed in declarations without double colons
(`::'); the double colons were introduced in Fortran 90, which also
introduced a standard syntax for initializing variables in type
declarations.
Examples of standard-conforming code equivalent to the above example
are:
! Fortran 90
INTEGER :: i = 1, j = 2
REAL :: x(2,2) = RESHAPE((/0.,0.,0.,1./),SHAPE(x))
! Fortran 77
INTEGER i, j
REAL x(2,2)
DATA i/1/, j/2/, x/3*0.,1./
Note that variables which are explicitly initialized in declarations
or in `DATA' statements automatically acquire the `SAVE' attribute.

File: gfortran.info, Node: Extensions to namelist, Next: X format descriptor without count field, Prev: Old-style variable initialization, Up: Extensions implemented in GNU Fortran
6.1.3 Extensions to namelist
----------------------------
GNU Fortran fully supports the Fortran 95 standard for namelist I/O
including array qualifiers, substrings and fully qualified derived
types. The output from a namelist write is compatible with namelist
read. The output has all names in upper case and indentation to column
1 after the namelist name. Two extensions are permitted:
Old-style use of `$' instead of `&'
$MYNML
X(:)%Y(2) = 1.0 2.0 3.0
CH(1:4) = "abcd"
$END
It should be noted that the default terminator is `/' rather than
`&END'.
Querying of the namelist when inputting from stdin. After at least
one space, entering `?' sends to stdout the namelist name and the names
of the variables in the namelist:
?
&mynml
x
x%y
ch
&end
Entering `=?' outputs the namelist to stdout, as if `WRITE(*,NML =
mynml)' had been called:
=?
&MYNML
X(1)%Y= 0.000000 , 1.000000 , 0.000000 ,
X(2)%Y= 0.000000 , 2.000000 , 0.000000 ,
X(3)%Y= 0.000000 , 3.000000 , 0.000000 ,
CH=abcd, /
To aid this dialog, when input is from stdin, errors send their
messages to stderr and execution continues, even if `IOSTAT' is set.
`PRINT' namelist is permitted. This causes an error if `-std=f95'
is used.
PROGRAM test_print
REAL, dimension (4) :: x = (/1.0, 2.0, 3.0, 4.0/)
NAMELIST /mynml/ x
PRINT mynml
END PROGRAM test_print
Expanded namelist reads are permitted. This causes an error if
`-std=f95' is used. In the following example, the first element of the
array will be given the value 0.00 and the two succeeding elements will
be given the values 1.00 and 2.00.
&MYNML
X(1,1) = 0.00 , 1.00 , 2.00
/

File: gfortran.info, Node: X format descriptor without count field, Next: Commas in FORMAT specifications, Prev: Extensions to namelist, Up: Extensions implemented in GNU Fortran
6.1.4 `X' format descriptor without count field
-----------------------------------------------
To support legacy codes, GNU Fortran permits the count field of the `X'
edit descriptor in `FORMAT' statements to be omitted. When omitted,
the count is implicitly assumed to be one.
PRINT 10, 2, 3
10 FORMAT (I1, X, I1)

File: gfortran.info, Node: Commas in FORMAT specifications, Next: Missing period in FORMAT specifications, Prev: X format descriptor without count field, Up: Extensions implemented in GNU Fortran
6.1.5 Commas in `FORMAT' specifications
---------------------------------------
To support legacy codes, GNU Fortran allows the comma separator to be
omitted immediately before and after character string edit descriptors
in `FORMAT' statements.
PRINT 10, 2, 3
10 FORMAT ('FOO='I1' BAR='I2)

File: gfortran.info, Node: Missing period in FORMAT specifications, Next: I/O item lists, Prev: Commas in FORMAT specifications, Up: Extensions implemented in GNU Fortran
6.1.6 Missing period in `FORMAT' specifications
-----------------------------------------------
To support legacy codes, GNU Fortran allows missing periods in format
specifications if and only if `-std=legacy' is given on the command
line. This is considered non-conforming code and is discouraged.
REAL :: value
READ(*,10) value
10 FORMAT ('F4')

File: gfortran.info, Node: I/O item lists, Next: BOZ literal constants, Prev: Missing period in FORMAT specifications, Up: Extensions implemented in GNU Fortran
6.1.7 I/O item lists
--------------------
To support legacy codes, GNU Fortran allows the input item list of the
`READ' statement, and the output item lists of the `WRITE' and `PRINT'
statements, to start with a comma.

File: gfortran.info, Node: BOZ literal constants, Next: Real array indices, Prev: I/O item lists, Up: Extensions implemented in GNU Fortran
6.1.8 BOZ literal constants
---------------------------
Besides decimal constants, Fortran also supports binary (`b'), octal
(`o') and hexadecimal (`z') integer constants. The syntax is: `prefix
quote digits quote', were the prefix is either `b', `o' or `z', quote
is either `'' or `"' and the digits are for binary `0' or `1', for
octal between `0' and `7', and for hexadecimal between `0' and `F'.
(Example: `b'01011101''.)
Up to Fortran 95, BOZ literals were only allowed to initialize
integer variables in DATA statements. Since Fortran 2003 BOZ literals
are also allowed as argument of `REAL', `DBLE', `INT' and `CMPLX'; the
result is the same as if the integer BOZ literal had been converted by
`TRANSFER' to, respectively, `real', `double precision', `integer' or
`complex'. As GNU Fortran extension the intrinsic procedures `FLOAT',
`DFLOAT', `COMPLEX' and `DCMPLX' are treated alike.
As an extension, GNU Fortran allows hexadecimal BOZ literal
constants to be specified using the `X' prefix, in addition to the
standard `Z' prefix. The BOZ literal can also be specified by adding a
suffix to the string, for example, `Z'ABC'' and `'ABC'Z' are equivalent.
Furthermore, GNU Fortran allows using BOZ literal constants outside
DATA statements and the four intrinsic functions allowed by Fortran
2003. In DATA statements, in direct assignments, where the right-hand
side only contains a BOZ literal constant, and for old-style
initializers of the form `integer i /o'0173'/', the constant is
transferred as if `TRANSFER' had been used; for `COMPLEX' numbers, only
the real part is initialized unless `CMPLX' is used. In all other
cases, the BOZ literal constant is converted to an `INTEGER' value with
the largest decimal representation. This value is then converted
numerically to the type and kind of the variable in question. (For
instance, `real :: r = b'0000001' + 1' initializes `r' with `2.0'.) As
different compilers implement the extension differently, one should be
careful when doing bitwise initialization of non-integer variables.
Note that initializing an `INTEGER' variable with a statement such
as `DATA i/Z'FFFFFFFF'/' will give an integer overflow error rather
than the desired result of -1 when `i' is a 32-bit integer on a system
that supports 64-bit integers. The `-fno-range-check' option can be
used as a workaround for legacy code that initializes integers in this
manner.

File: gfortran.info, Node: Real array indices, Next: Unary operators, Prev: BOZ literal constants, Up: Extensions implemented in GNU Fortran
6.1.9 Real array indices
------------------------
As an extension, GNU Fortran allows the use of `REAL' expressions or
variables as array indices.

File: gfortran.info, Node: Unary operators, Next: Implicitly convert LOGICAL and INTEGER values, Prev: Real array indices, Up: Extensions implemented in GNU Fortran
6.1.10 Unary operators
----------------------
As an extension, GNU Fortran allows unary plus and unary minus operators
to appear as the second operand of binary arithmetic operators without
the need for parenthesis.
X = Y * -Z

File: gfortran.info, Node: Implicitly convert LOGICAL and INTEGER values, Next: Hollerith constants support, Prev: Unary operators, Up: Extensions implemented in GNU Fortran
6.1.11 Implicitly convert `LOGICAL' and `INTEGER' values
--------------------------------------------------------
As an extension for backwards compatibility with other compilers, GNU
Fortran allows the implicit conversion of `LOGICAL' values to `INTEGER'
values and vice versa. When converting from a `LOGICAL' to an
`INTEGER', `.FALSE.' is interpreted as zero, and `.TRUE.' is
interpreted as one. When converting from `INTEGER' to `LOGICAL', the
value zero is interpreted as `.FALSE.' and any nonzero value is
interpreted as `.TRUE.'.
LOGICAL :: l
l = 1
INTEGER :: i
i = .TRUE.
However, there is no implicit conversion of `INTEGER' values in
`if'-statements, nor of `LOGICAL' or `INTEGER' values in I/O operations.

File: gfortran.info, Node: Hollerith constants support, Next: Cray pointers, Prev: Implicitly convert LOGICAL and INTEGER values, Up: Extensions implemented in GNU Fortran
6.1.12 Hollerith constants support
----------------------------------
GNU Fortran supports Hollerith constants in assignments, function
arguments, and `DATA' and `ASSIGN' statements. A Hollerith constant is
written as a string of characters preceded by an integer constant
indicating the character count, and the letter `H' or `h', and stored
in bytewise fashion in a numeric (`INTEGER', `REAL', or `complex') or
`LOGICAL' variable. The constant will be padded or truncated to fit
the size of the variable in which it is stored.
Examples of valid uses of Hollerith constants:
complex*16 x(2)
data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/
x(1) = 16HABCDEFGHIJKLMNOP
call foo (4h abc)
Invalid Hollerith constants examples:
integer*4 a
a = 8H12345678 ! Valid, but the Hollerith constant will be truncated.
a = 0H ! At least one character is needed.
In general, Hollerith constants were used to provide a rudimentary
facility for handling character strings in early Fortran compilers,
prior to the introduction of `CHARACTER' variables in Fortran 77; in
those cases, the standard-compliant equivalent is to convert the
program to use proper character strings. On occasion, there may be a
case where the intent is specifically to initialize a numeric variable
with a given byte sequence. In these cases, the same result can be
obtained by using the `TRANSFER' statement, as in this example.
INTEGER(KIND=4) :: a
a = TRANSFER ("abcd", a) ! equivalent to: a = 4Habcd

File: gfortran.info, Node: Cray pointers, Next: CONVERT specifier, Prev: Hollerith constants support, Up: Extensions implemented in GNU Fortran
6.1.13 Cray pointers
--------------------
Cray pointers are part of a non-standard extension that provides a
C-like pointer in Fortran. This is accomplished through a pair of
variables: an integer "pointer" that holds a memory address, and a
"pointee" that is used to dereference the pointer.
Pointer/pointee pairs are declared in statements of the form:
pointer ( <pointer> , <pointee> )
or,
pointer ( <pointer1> , <pointee1> ), ( <pointer2> , <pointee2> ), ...
The pointer is an integer that is intended to hold a memory address.
The pointee may be an array or scalar. A pointee can be an assumed
size array--that is, the last dimension may be left unspecified by
using a `*' in place of a value--but a pointee cannot be an assumed
shape array. No space is allocated for the pointee.
The pointee may have its type declared before or after the pointer
statement, and its array specification (if any) may be declared before,
during, or after the pointer statement. The pointer may be declared as
an integer prior to the pointer statement. However, some machines have
default integer sizes that are different than the size of a pointer,
and so the following code is not portable:
integer ipt
pointer (ipt, iarr)
If a pointer is declared with a kind that is too small, the compiler
will issue a warning; the resulting binary will probably not work
correctly, because the memory addresses stored in the pointers may be
truncated. It is safer to omit the first line of the above example; if
explicit declaration of ipt's type is omitted, then the compiler will
ensure that ipt is an integer variable large enough to hold a pointer.
Pointer arithmetic is valid with Cray pointers, but it is not the
same as C pointer arithmetic. Cray pointers are just ordinary
integers, so the user is responsible for determining how many bytes to
add to a pointer in order to increment it. Consider the following
example:
real target(10)
real pointee(10)
pointer (ipt, pointee)
ipt = loc (target)
ipt = ipt + 1
The last statement does not set `ipt' to the address of `target(1)',
as it would in C pointer arithmetic. Adding `1' to `ipt' just adds one
byte to the address stored in `ipt'.
Any expression involving the pointee will be translated to use the
value stored in the pointer as the base address.
To get the address of elements, this extension provides an intrinsic
function `LOC()'. The `LOC()' function is equivalent to the `&'
operator in C, except the address is cast to an integer type:
real ar(10)
pointer(ipt, arpte(10))
real arpte
ipt = loc(ar) ! Makes arpte is an alias for ar
arpte(1) = 1.0 ! Sets ar(1) to 1.0
The pointer can also be set by a call to the `MALLOC' intrinsic (see
*Note MALLOC::).
Cray pointees often are used to alias an existing variable. For
example:
integer target(10)
integer iarr(10)
pointer (ipt, iarr)
ipt = loc(target)
As long as `ipt' remains unchanged, `iarr' is now an alias for
`target'. The optimizer, however, will not detect this aliasing, so it
is unsafe to use `iarr' and `target' simultaneously. Using a pointee
in any way that violates the Fortran aliasing rules or assumptions is
illegal. It is the user's responsibility to avoid doing this; the
compiler works under the assumption that no such aliasing occurs.
Cray pointers will work correctly when there is no aliasing (i.e.,
when they are used to access a dynamically allocated block of memory),
and also in any routine where a pointee is used, but any variable with
which it shares storage is not used. Code that violates these rules
may not run as the user intends. This is not a bug in the optimizer;
any code that violates the aliasing rules is illegal. (Note that this
is not unique to GNU Fortran; any Fortran compiler that supports Cray
pointers will "incorrectly" optimize code with illegal aliasing.)
There are a number of restrictions on the attributes that can be
applied to Cray pointers and pointees. Pointees may not have the
`ALLOCATABLE', `INTENT', `OPTIONAL', `DUMMY', `TARGET', `INTRINSIC', or
`POINTER' attributes. Pointers may not have the `DIMENSION', `POINTER',
`TARGET', `ALLOCATABLE', `EXTERNAL', or `INTRINSIC' attributes.
Pointees may not occur in more than one pointer statement. A pointee
cannot be a pointer. Pointees cannot occur in equivalence, common, or
data statements.
A Cray pointer may also point to a function or a subroutine. For
example, the following excerpt is valid:
implicit none
external sub
pointer (subptr,subpte)
external subpte
subptr = loc(sub)
call subpte()
[...]
subroutine sub
[...]
end subroutine sub
A pointer may be modified during the course of a program, and this
will change the location to which the pointee refers. However, when
pointees are passed as arguments, they are treated as ordinary
variables in the invoked function. Subsequent changes to the pointer
will not change the base address of the array that was passed.

File: gfortran.info, Node: CONVERT specifier, Next: OpenMP, Prev: Cray pointers, Up: Extensions implemented in GNU Fortran
6.1.14 `CONVERT' specifier
--------------------------
GNU Fortran allows the conversion of unformatted data between little-
and big-endian representation to facilitate moving of data between
different systems. The conversion can be indicated with the `CONVERT'
specifier on the `OPEN' statement. *Note GFORTRAN_CONVERT_UNIT::, for
an alternative way of specifying the data format via an environment
variable.
Valid values for `CONVERT' are:
`CONVERT='NATIVE'' Use the native format. This is the default.
`CONVERT='SWAP'' Swap between little- and big-endian.
`CONVERT='LITTLE_ENDIAN'' Use the little-endian representation for
unformatted files.
`CONVERT='BIG_ENDIAN'' Use the big-endian representation for
unformatted files.
Using the option could look like this:
open(file='big.dat',form='unformatted',access='sequential', &
convert='big_endian')
The value of the conversion can be queried by using
`INQUIRE(CONVERT=ch)'. The values returned are `'BIG_ENDIAN'' and
`'LITTLE_ENDIAN''.
`CONVERT' works between big- and little-endian for `INTEGER' values
of all supported kinds and for `REAL' on IEEE systems of kinds 4 and 8.
Conversion between different "extended double" types on different
architectures such as m68k and x86_64, which GNU Fortran supports as
`REAL(KIND=10)' and `REAL(KIND=16)', will probably not work.
_Note that the values specified via the GFORTRAN_CONVERT_UNIT
environment variable will override the CONVERT specifier in the open
statement_. This is to give control over data formats to users who do
not have the source code of their program available.
Using anything but the native representation for unformatted data
carries a significant speed overhead. If speed in this area matters to
you, it is best if you use this only for data that needs to be portable.

File: gfortran.info, Node: OpenMP, Next: Argument list functions, Prev: CONVERT specifier, Up: Extensions implemented in GNU Fortran
6.1.15 OpenMP
-------------
OpenMP (Open Multi-Processing) is an application programming interface
(API) that supports multi-platform shared memory multiprocessing
programming in C/C++ and Fortran on many architectures, including Unix
and Microsoft Windows platforms. It consists of a set of compiler
directives, library routines, and environment variables that influence
run-time behavior.
GNU Fortran strives to be compatible to the OpenMP Application
Program Interface v3.0 (http://www.openmp.org/mp-documents/spec30.pdf).
To enable the processing of the OpenMP directive `!$omp' in
free-form source code; the `c$omp', `*$omp' and `!$omp' directives in
fixed form; the `!$' conditional compilation sentinels in free form;
and the `c$', `*$' and `!$' sentinels in fixed form, `gfortran' needs
to be invoked with the `-fopenmp'. This also arranges for automatic
linking of the GNU OpenMP runtime library *Note libgomp: (libgomp)Top.
The OpenMP Fortran runtime library routines are provided both in a
form of a Fortran 90 module named `omp_lib' and in a form of a Fortran
`include' file named `omp_lib.h'.
An example of a parallelized loop taken from Appendix A.1 of the
OpenMP Application Program Interface v2.5:
SUBROUTINE A1(N, A, B)
INTEGER I, N
REAL B(N), A(N)
!$OMP PARALLEL DO !I is private by default
DO I=2,N
B(I) = (A(I) + A(I-1)) / 2.0
ENDDO
!$OMP END PARALLEL DO
END SUBROUTINE A1
Please note:
* `-fopenmp' implies `-frecursive', i.e., all local arrays will be
allocated on the stack. When porting existing code to OpenMP, this
may lead to surprising results, especially to segmentation faults
if the stacksize is limited.
* On glibc-based systems, OpenMP enabled applications cannot be
statically linked due to limitations of the underlying
pthreads-implementation. It might be possible to get a working
solution if `-Wl,--whole-archive -lpthread -Wl,--no-whole-archive'
is added to the command line. However, this is not supported by
`gcc' and thus not recommended.

File: gfortran.info, Node: Argument list functions, Prev: OpenMP, Up: Extensions implemented in GNU Fortran
6.1.16 Argument list functions `%VAL', `%REF' and `%LOC'
--------------------------------------------------------
GNU Fortran supports argument list functions `%VAL', `%REF' and `%LOC'
statements, for backward compatibility with g77. It is recommended
that these should be used only for code that is accessing facilities
outside of GNU Fortran, such as operating system or windowing
facilities. It is best to constrain such uses to isolated portions of a
program-portions that deal specifically and exclusively with low-level,
system-dependent facilities. Such portions might well provide a
portable interface for use by the program as a whole, but are
themselves not portable, and should be thoroughly tested each time they
are rebuilt using a new compiler or version of a compiler.
`%VAL' passes a scalar argument by value, `%REF' passes it by
reference and `%LOC' passes its memory location. Since gfortran
already passes scalar arguments by reference, `%REF' is in effect a
do-nothing. `%LOC' has the same effect as a Fortran pointer.
An example of passing an argument by value to a C subroutine foo.:
C
C prototype void foo_ (float x);
C
external foo
real*4 x
x = 3.14159
call foo (%VAL (x))
end
For details refer to the g77 manual
`http://gcc.gnu.org/onlinedocs/gcc-3.4.6/g77/index.html#Top'.
Also, `c_by_val.f' and its partner `c_by_val.c' of the GNU Fortran
testsuite are worth a look.

File: gfortran.info, Node: Extensions not implemented in GNU Fortran, Prev: Extensions implemented in GNU Fortran, Up: Extensions
6.2 Extensions not implemented in GNU Fortran
=============================================
The long history of the Fortran language, its wide use and broad
userbase, the large number of different compiler vendors and the lack of
some features crucial to users in the first standards have lead to the
existence of a number of important extensions to the language. While
some of the most useful or popular extensions are supported by the GNU
Fortran compiler, not all existing extensions are supported. This
section aims at listing these extensions and offering advice on how
best make code that uses them running with the GNU Fortran compiler.
* Menu:
* STRUCTURE and RECORD::
* ENCODE and DECODE statements::
* Variable FORMAT expressions::

File: gfortran.info, Node: STRUCTURE and RECORD, Next: ENCODE and DECODE statements, Up: Extensions not implemented in GNU Fortran
6.2.1 `STRUCTURE' and `RECORD'
------------------------------
Structures are user-defined aggregate data types; this functionality was
standardized in Fortran 90 with an different syntax, under the name of
"derived types". Here is an example of code using the non portable
structure syntax:
! Declaring a structure named ``item'' and containing three fields:
! an integer ID, an description string and a floating-point price.
STRUCTURE /item/
INTEGER id
CHARACTER(LEN=200) description
REAL price
END STRUCTURE
! Define two variables, an single record of type ``item''
! named ``pear'', and an array of items named ``store_catalog''
RECORD /item/ pear, store_catalog(100)
! We can directly access the fields of both variables
pear.id = 92316
pear.description = "juicy D'Anjou pear"
pear.price = 0.15
store_catalog(7).id = 7831
store_catalog(7).description = "milk bottle"
store_catalog(7).price = 1.2
! We can also manipulate the whole structure
store_catalog(12) = pear
print *, store_catalog(12)
This code can easily be rewritten in the Fortran 90 syntax as following:
! ``STRUCTURE /name/ ... END STRUCTURE'' becomes
! ``TYPE name ... END TYPE''
TYPE item
INTEGER id
CHARACTER(LEN=200) description
REAL price
END TYPE
! ``RECORD /name/ variable'' becomes ``TYPE(name) variable''
TYPE(item) pear, store_catalog(100)
! Instead of using a dot (.) to access fields of a record, the
! standard syntax uses a percent sign (%)
pear%id = 92316
pear%description = "juicy D'Anjou pear"
pear%price = 0.15
store_catalog(7)%id = 7831
store_catalog(7)%description = "milk bottle"
store_catalog(7)%price = 1.2
! Assignments of a whole variable don't change
store_catalog(12) = pear
print *, store_catalog(12)

File: gfortran.info, Node: ENCODE and DECODE statements, Next: Variable FORMAT expressions, Prev: STRUCTURE and RECORD, Up: Extensions not implemented in GNU Fortran
6.2.2 `ENCODE' and `DECODE' statements
--------------------------------------
GNU Fortran doesn't support the `ENCODE' and `DECODE' statements.
These statements are best replaced by `READ' and `WRITE' statements
involving internal files (`CHARACTER' variables and arrays), which have
been part of the Fortran standard since Fortran 77. For example,
replace a code fragment like
INTEGER*1 LINE(80)
REAL A, B, C
c ... Code that sets LINE
DECODE (80, 9000, LINE) A, B, C
9000 FORMAT (1X, 3(F10.5))
with the following:
CHARACTER(LEN=80) LINE
REAL A, B, C
c ... Code that sets LINE
READ (UNIT=LINE, FMT=9000) A, B, C
9000 FORMAT (1X, 3(F10.5))
Similarly, replace a code fragment like
INTEGER*1 LINE(80)
REAL A, B, C
c ... Code that sets A, B and C
ENCODE (80, 9000, LINE) A, B, C
9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))
with the following:
CHARACTER(LEN=80) LINE
REAL A, B, C
c ... Code that sets A, B and C
WRITE (UNIT=LINE, FMT=9000) A, B, C
9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))

File: gfortran.info, Node: Variable FORMAT expressions, Prev: ENCODE and DECODE statements, Up: Extensions not implemented in GNU Fortran
6.2.3 Variable `FORMAT' expressions
-----------------------------------
A variable `FORMAT' expression is format statement which includes angle
brackets enclosing a Fortran expression: `FORMAT(I<N>)'. GNU Fortran
does not support this legacy extension. The effect of variable format
expressions can be reproduced by using the more powerful (and standard)
combination of internal output and string formats. For example, replace
a code fragment like this:
WRITE(6,20) INT1
20 FORMAT(I<N+1>)
with the following:
c Variable declaration
CHARACTER(LEN=20) F
c
c Other code here...
c
WRITE(FMT,'("(I", I0, ")")') N+1
WRITE(6,FM) INT1
or with:
c Variable declaration
CHARACTER(LEN=20) FMT
c
c Other code here...
c
WRITE(FMT,*) N+1
WRITE(6,"(I" // ADJUSTL(FMT) // ")") INT1

File: gfortran.info, Node: Mixed-Language Programming, Next: Extensions, Prev: Compiler Characteristics, Up: Top
7 Mixed-Language Programming
****************************
* Menu:
* Interoperability with C::
* GNU Fortran Compiler Directives::
* Non-Fortran Main Program::
This chapter is about mixed-language interoperability, but also
applies if one links Fortran code compiled by different compilers. In
most cases, use of the C Binding features of the Fortran 2003 standard
is sufficient, and their use is highly recommended.

File: gfortran.info, Node: Interoperability with C, Next: GNU Fortran Compiler Directives, Up: Mixed-Language Programming
7.1 Interoperability with C
===========================
* Menu:
* Intrinsic Types::
* Further Interoperability of Fortran with C::
* Derived Types and struct::
* Interoperable Global Variables::
* Interoperable Subroutines and Functions::
Since Fortran 2003 (ISO/IEC 1539-1:2004(E)) there is a standardized
way to generate procedure and derived-type declarations and global
variables which are interoperable with C (ISO/IEC 9899:1999). The
`bind(C)' attribute has been added to inform the compiler that a symbol
shall be interoperable with C; also, some constraints are added. Note,
however, that not all C features have a Fortran equivalent or vice
versa. For instance, neither C's unsigned integers nor C's functions
with variable number of arguments have an equivalent in Fortran.
Note that array dimensions are reversely ordered in C and that
arrays in C always start with index 0 while in Fortran they start by
default with 1. Thus, an array declaration `A(n,m)' in Fortran matches
`A[m][n]' in C and accessing the element `A(i,j)' matches
`A[j-1][i-1]'. The element following `A(i,j)' (C: `A[j-1][i-1]';
assuming i < n) in memory is `A(i+1,j)' (C: `A[j-1][i]').

File: gfortran.info, Node: Intrinsic Types, Next: Further Interoperability of Fortran with C, Up: Interoperability with C
7.1.1 Intrinsic Types
---------------------
In order to ensure that exactly the same variable type and kind is used
in C and Fortran, the named constants shall be used which are defined
in the `ISO_C_BINDING' intrinsic module. That module contains named
constants for kind parameters and character named constants for the
escape sequences in C. For a list of the constants, see *Note
ISO_C_BINDING::.

File: gfortran.info, Node: Derived Types and struct, Next: Interoperable Global Variables, Prev: Further Interoperability of Fortran with C, Up: Interoperability with C
7.1.2 Derived Types and struct
------------------------------
For compatibility of derived types with `struct', one needs to use the
`BIND(C)' attribute in the type declaration. For instance, the
following type declaration
USE ISO_C_BINDING
TYPE, BIND(C) :: myType
INTEGER(C_INT) :: i1, i2
INTEGER(C_SIGNED_CHAR) :: i3
REAL(C_DOUBLE) :: d1
COMPLEX(C_FLOAT_COMPLEX) :: c1
CHARACTER(KIND=C_CHAR) :: str(5)
END TYPE
matches the following `struct' declaration in C
struct {
int i1, i2;
/* Note: "char" might be signed or unsigned. */
signed char i3;
double d1;
float _Complex c1;
char str[5];
} myType;
Derived types with the C binding attribute shall not have the
`sequence' attribute, type parameters, the `extends' attribute, nor
type-bound procedures. Every component must be of interoperable type
and kind and may not have the `pointer' or `allocatable' attribute. The
names of the variables are irrelevant for interoperability.
As there exist no direct Fortran equivalents, neither unions nor
structs with bit field or variable-length array members are
interoperable.

File: gfortran.info, Node: Interoperable Global Variables, Next: Interoperable Subroutines and Functions, Prev: Derived Types and struct, Up: Interoperability with C
7.1.3 Interoperable Global Variables
------------------------------------
Variables can be made accessible from C using the C binding attribute,
optionally together with specifying a binding name. Those variables
have to be declared in the declaration part of a `MODULE', be of
interoperable type, and have neither the `pointer' nor the
`allocatable' attribute.
MODULE m
USE myType_module
USE ISO_C_BINDING
integer(C_INT), bind(C, name="_MyProject_flags") :: global_flag
type(myType), bind(C) :: tp
END MODULE
Here, `_MyProject_flags' is the case-sensitive name of the variable
as seen from C programs while `global_flag' is the case-insensitive
name as seen from Fortran. If no binding name is specified, as for TP,
the C binding name is the (lowercase) Fortran binding name. If a
binding name is specified, only a single variable may be after the
double colon. Note of warning: You cannot use a global variable to
access ERRNO of the C library as the C standard allows it to be a
macro. Use the `IERRNO' intrinsic (GNU extension) instead.

File: gfortran.info, Node: Interoperable Subroutines and Functions, Prev: Interoperable Global Variables, Up: Interoperability with C
7.1.4 Interoperable Subroutines and Functions
---------------------------------------------
Subroutines and functions have to have the `BIND(C)' attribute to be
compatible with C. The dummy argument declaration is relatively
straightforward. However, one needs to be careful because C uses
call-by-value by default while Fortran behaves usually similar to
call-by-reference. Furthermore, strings and pointers are handled
differently. Note that only explicit size and assumed-size arrays are
supported but not assumed-shape or allocatable arrays.
To pass a variable by value, use the `VALUE' attribute. Thus the
following C prototype
`int func(int i, int *j)'
matches the Fortran declaration
integer(c_int) function func(i,j)
use iso_c_binding, only: c_int
integer(c_int), VALUE :: i
integer(c_int) :: j
Note that pointer arguments also frequently need the `VALUE'
attribute.
Strings are handled quite differently in C and Fortran. In C a string
is a `NUL'-terminated array of characters while in Fortran each string
has a length associated with it and is thus not terminated (by e.g.
`NUL'). For example, if one wants to use the following C function,
#include <stdio.h>
void print_C(char *string) /* equivalent: char string[] */
{
printf("%s\n", string);
}
to print "Hello World" from Fortran, one can call it using
use iso_c_binding, only: C_CHAR, C_NULL_CHAR
interface
subroutine print_c(string) bind(C, name="print_C")
use iso_c_binding, only: c_char
character(kind=c_char) :: string(*)
end subroutine print_c
end interface
call print_c(C_CHAR_"Hello World"//C_NULL_CHAR)
As the example shows, one needs to ensure that the string is `NUL'
terminated. Additionally, the dummy argument STRING of `print_C' is a
length-one assumed-size array; using `character(len=*)' is not allowed.
The example above uses `c_char_"Hello World"' to ensure the string
literal has the right type; typically the default character kind and
`c_char' are the same and thus `"Hello World"' is equivalent. However,
the standard does not guarantee this.
The use of pointers is now illustrated using the C library function
`strncpy', whose prototype is
char *strncpy(char *restrict s1, const char *restrict s2, size_t n);
The function `strncpy' copies at most N characters from string S2 to
S1 and returns S1. In the following example, we ignore the return value:
use iso_c_binding
implicit none
character(len=30) :: str,str2
interface
! Ignore the return value of strncpy -> subroutine
! "restrict" is always assumed if we do not pass a pointer
subroutine strncpy(dest, src, n) bind(C)
import
character(kind=c_char), intent(out) :: dest(*)
character(kind=c_char), intent(in) :: src(*)
integer(c_size_t), value, intent(in) :: n
end subroutine strncpy
end interface
str = repeat('X',30) ! Initialize whole string with 'X'
call strncpy(str, c_char_"Hello World"//C_NULL_CHAR, &
len(c_char_"Hello World",kind=c_size_t))
print '(a)', str ! prints: "Hello WorldXXXXXXXXXXXXXXXXXXX"
end
C pointers are represented in Fortran via the special derived type
`type(c_ptr)', with private components. Thus one needs to use intrinsic
conversion procedures to convert from or to C pointers. For example,
use iso_c_binding
type(c_ptr) :: cptr1, cptr2
integer, target :: array(7), scalar
integer, pointer :: pa(:), ps
cptr1 = c_loc(array(1)) ! The programmer needs to ensure that the
! array is contiguous if required by the C
! procedure
cptr2 = c_loc(scalar)
call c_f_pointer(cptr2, ps)
call c_f_pointer(cptr2, pa, shape=[7])
When converting C to Fortran arrays, the one-dimensional `SHAPE'
argument has to be passed. Note: A pointer argument `void *' matches
`TYPE(C_PTR), VALUE' while `TYPE(C_PTR)' matches `void **'.
Procedure pointers are handled analogously to pointers; the C type is
`TYPE(C_FUNPTR)' and the intrinsic conversion procedures are
`C_F_PROC_POINTER' and `C_FUNLOC'.
The intrinsic procedures are described in *Note Intrinsic
Procedures::.

File: gfortran.info, Node: Further Interoperability of Fortran with C, Next: Derived Types and struct, Prev: Intrinsic Types, Up: Interoperability with C
7.1.5 Further Interoperability of Fortran with C
------------------------------------------------
Assumed-shape and allocatable arrays are passed using an array
descriptor (dope vector). The internal structure of the array
descriptor used by GNU Fortran is not yet documented and will change.
There will also be a Technical Report (TR 29113) which standardizes an
interoperable array descriptor. Until then, you can use the Chasm
Language Interoperability Tools,
`http://chasm-interop.sourceforge.net/', which provide an interface to
GNU Fortran's array descriptor.
The technical report 29113 will presumably also include support for
C-interoperable `OPTIONAL' and for assumed-rank and assumed-type dummy
arguments. However, the TR has neither been approved nor implemented in
GNU Fortran; therefore, these features are not yet available.

File: gfortran.info, Node: GNU Fortran Compiler Directives, Next: Non-Fortran Main Program, Prev: Interoperability with C, Up: Mixed-Language Programming
7.2 GNU Fortran Compiler Directives
===================================
The Fortran standard standard describes how a conforming program shall
behave; however, the exact implementation is not standardized. In order
to allow the user to choose specific implementation details, compiler
directives can be used to set attributes of variables and procedures
which are not part of the standard. Whether a given attribute is
supported and its exact effects depend on both the operating system and
on the processor; see *Note C Extensions: (gcc)Top. for details.
For procedures and procedure pointers, the following attributes can
be used to change the calling convention:
* `CDECL' - standard C calling convention
* `STDCALL' - convention where the called procedure pops the stack
* `FASTCALL' - part of the arguments are passed via registers
instead using the stack
Besides changing the calling convention, the attributes also
influence the decoration of the symbol name, e.g., by a leading
underscore or by a trailing at-sign followed by the number of bytes on
the stack. When assigning a procedure to a procedure pointer, both
should use the same calling convention.
On some systems, procedures and global variables (module variables
and `COMMON' blocks) need special handling to be accessible when they
are in a shared library. The following attributes are available:
* `DLLEXPORT' - provide a global pointer to a pointer in the DLL
* `DLLIMPORT' - reference the function or variable using a global
pointer
The attributes are specified using the syntax
`!GCC$ ATTRIBUTES' ATTRIBUTE-LIST `::' VARIABLE-LIST
where in free-form source code only whitespace is allowed before
`!GCC$' and in fixed-form source code `!GCC$', `cGCC$' or `*GCC$' shall
start in the first column.
For procedures, the compiler directives shall be placed into the body
of the procedure; for variables and procedure pointers, they shall be in
the same declaration part as the variable or procedure pointer.

File: gfortran.info, Node: Non-Fortran Main Program, Prev: GNU Fortran Compiler Directives, Up: Mixed-Language Programming
7.3 Non-Fortran Main Program
============================
* Menu:
* _gfortran_set_args:: Save command-line arguments
* _gfortran_set_options:: Set library option flags
* _gfortran_set_convert:: Set endian conversion
* _gfortran_set_record_marker:: Set length of record markers
* _gfortran_set_max_subrecord_length:: Set subrecord length
* _gfortran_set_fpe:: Set when a Floating Point Exception should be raised
Even if you are doing mixed-language programming, it is very likely
that you do not need to know or use the information in this section.
Since it is about the internal structure of GNU Fortran, it may also
change in GCC minor releases.
When you compile a `PROGRAM' with GNU Fortran, a function with the
name `main' (in the symbol table of the object file) is generated,
which initializes the libgfortran library and then calls the actual
program which uses the name `MAIN__', for historic reasons. If you link
GNU Fortran compiled procedures to, e.g., a C or C++ program or to a
Fortran program compiled by a different compiler, the libgfortran
library is not initialized and thus a few intrinsic procedures do not
work properly, e.g. those for obtaining the command-line arguments.
Therefore, if your `PROGRAM' is not compiled with GNU Fortran and
the GNU Fortran compiled procedures require intrinsics relying on the
library initialization, you need to initialize the library yourself.
Using the default options, gfortran calls `_gfortran_set_args' and
`_gfortran_set_options'. The initialization of the former is needed if
the called procedures access the command line (and for backtracing);
the latter sets some flags based on the standard chosen or to enable
backtracing. In typical programs, it is not necessary to call any
initialization function.
If your `PROGRAM' is compiled with GNU Fortran, you shall not call
any of the following functions. The libgfortran initialization
functions are shown in C syntax but using C bindings they are also
accessible from Fortran.

File: gfortran.info, Node: _gfortran_set_args, Next: _gfortran_set_options, Up: Non-Fortran Main Program
7.3.1 `_gfortran_set_args' -- Save command-line arguments
---------------------------------------------------------
_Description_:
`_gfortran_set_args' saves the command-line arguments; this
initialization is required if any of the command-line intrinsics
is called. Additionally, it shall be called if backtracing is
enabled (see `_gfortran_set_options').
_Syntax_:
`void _gfortran_set_args (int argc, char *argv[])'
_Arguments_:
ARGC number of command line argument strings
ARGV the command-line argument strings; argv[0] is
the pathname of the executable itself.
_Example_:
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
return 0;
}

File: gfortran.info, Node: _gfortran_set_options, Next: _gfortran_set_convert, Prev: _gfortran_set_args, Up: Non-Fortran Main Program
7.3.2 `_gfortran_set_options' -- Set library option flags
---------------------------------------------------------
_Description_:
`_gfortran_set_options' sets several flags related to the Fortran
standard to be used, whether backtracing or core dumps should be
enabled and whether range checks should be performed. The syntax
allows for upward compatibility since the number of passed flags
is specified; for non-passed flags, the default value is used. See
also *note Code Gen Options::. Please note that not all flags are
actually used.
_Syntax_:
`void _gfortran_set_options (int num, int options[])'
_Arguments_:
NUM number of options passed
ARGV The list of flag values
_option flag list_:
OPTION[0] Allowed standard; can give run-time errors if
e.g. an input-output edit descriptor is
invalid in a given standard. Possible values
are (bitwise or-ed) `GFC_STD_F77' (1),
`GFC_STD_F95_OBS' (2), `GFC_STD_F95_DEL' (4),
`GFC_STD_F95' (8), `GFC_STD_F2003' (16),
`GFC_STD_GNU' (32), `GFC_STD_LEGACY' (64), and
`GFC_STD_F2008' (128). Default:
`GFC_STD_F95_OBS | GFC_STD_F95_DEL |
GFC_STD_F2003 | GFC_STD_F2008 | GFC_STD_F95 |
GFC_STD_F77 | GFC_STD_GNU | GFC_STD_LEGACY'.
OPTION[1] Standard-warning flag; prints a warning to
standard error. Default: `GFC_STD_F95_DEL |
GFC_STD_LEGACY'.
OPTION[2] If non zero, enable pedantic checking.
Default: off.
OPTION[3] If non zero, enable core dumps on run-time
errors. Default: off.
OPTION[4] If non zero, enable backtracing on run-time
errors. Default: off. Note: Installs a signal
handler and requires command-line
initialization using `_gfortran_set_args'.
OPTION[5] If non zero, supports signed zeros. Default:
enabled.
OPTION[6] Enables run-time checking. Possible values are
(bitwise or-ed): GFC_RTCHECK_BOUNDS (1),
GFC_RTCHECK_ARRAY_TEMPS (2),
GFC_RTCHECK_RECURSION (4), GFC_RTCHECK_DO
(16), GFC_RTCHECK_POINTER (32). Default:
disabled.
OPTION[7] If non zero, range checking is enabled.
Default: enabled. See -frange-check (*note
Code Gen Options::).
_Example_:
/* Use gfortran 4.5 default options. */
static int options[] = {68, 255, 0, 0, 0, 1, 0, 1};
_gfortran_set_options (8, &options);

File: gfortran.info, Node: _gfortran_set_convert, Next: _gfortran_set_record_marker, Prev: _gfortran_set_options, Up: Non-Fortran Main Program
7.3.3 `_gfortran_set_convert' -- Set endian conversion
------------------------------------------------------
_Description_:
`_gfortran_set_convert' set the representation of data for
unformatted files.
_Syntax_:
`void _gfortran_set_convert (int conv)'
_Arguments_:
CONV Endian conversion, possible values:
GFC_CONVERT_NATIVE (0, default),
GFC_CONVERT_SWAP (1), GFC_CONVERT_BIG (2),
GFC_CONVERT_LITTLE (3).
_Example_:
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_convert (1);
return 0;
}

File: gfortran.info, Node: _gfortran_set_record_marker, Next: _gfortran_set_max_subrecord_length, Prev: _gfortran_set_convert, Up: Non-Fortran Main Program
7.3.4 `_gfortran_set_record_marker' -- Set length of record markers
-------------------------------------------------------------------
_Description_:
`_gfortran_set_record_marker' sets the length of record markers
for unformatted files.
_Syntax_:
`void _gfortran_set_record_marker (int val)'
_Arguments_:
VAL Length of the record marker; valid values are
4 and 8. Default is 4.
_Example_:
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_record_marker (8);
return 0;
}

File: gfortran.info, Node: _gfortran_set_fpe, Prev: _gfortran_set_max_subrecord_length, Up: Non-Fortran Main Program
7.3.5 `_gfortran_set_fpe' -- Set when a Floating Point Exception should be raised
---------------------------------------------------------------------------------
_Description_:
`_gfortran_set_fpe' sets the IEEE exceptions for which a Floating
Point Exception (FPE) should be raised. On most systems, this will
result in a SIGFPE signal being sent and the program being
interrupted.
_Syntax_:
`void _gfortran_set_fpe (int val)'
_Arguments_:
OPTION[0] IEEE exceptions. Possible values are (bitwise
or-ed) zero (0, default) no trapping,
`GFC_FPE_INVALID' (1), `GFC_FPE_DENORMAL' (2),
`GFC_FPE_ZERO' (4), `GFC_FPE_OVERFLOW' (8),
`GFC_FPE_UNDERFLOW' (16), and
`GFC_FPE_PRECISION' (32).
_Example_:
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
/* FPE for invalid operations such as SQRT(-1.0). */
_gfortran_set_fpe (1);
return 0;
}

File: gfortran.info, Node: _gfortran_set_max_subrecord_length, Next: _gfortran_set_fpe, Prev: _gfortran_set_record_marker, Up: Non-Fortran Main Program
7.3.6 `_gfortran_set_max_subrecord_length' -- Set subrecord length
------------------------------------------------------------------
_Description_:
`_gfortran_set_max_subrecord_length' set the maximum length for a
subrecord. This option only makes sense for testing and debugging
of unformatted I/O.
_Syntax_:
`void _gfortran_set_max_subrecord_length (int val)'
_Arguments_:
VAL the maximum length for a subrecord; the
maximum permitted value is 2147483639, which
is also the default.
_Example_:
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_max_subrecord_length (8);
return 0;
}

File: gfortran.info, Node: Intrinsic Procedures, Next: Intrinsic Modules, Prev: Extensions, Up: Top
8 Intrinsic Procedures
**********************
* Menu:
* Introduction: Introduction to Intrinsics
* `ABORT': ABORT, Abort the program
* `ABS': ABS, Absolute value
* `ACCESS': ACCESS, Checks file access modes
* `ACHAR': ACHAR, Character in ASCII collating sequence
* `ACOS': ACOS, Arccosine function
* `ACOSH': ACOSH, Inverse hyperbolic cosine function
* `ADJUSTL': ADJUSTL, Left adjust a string
* `ADJUSTR': ADJUSTR, Right adjust a string
* `AIMAG': AIMAG, Imaginary part of complex number
* `AINT': AINT, Truncate to a whole number
* `ALARM': ALARM, Set an alarm clock
* `ALL': ALL, Determine if all values are true
* `ALLOCATED': ALLOCATED, Status of allocatable entity
* `AND': AND, Bitwise logical AND
* `ANINT': ANINT, Nearest whole number
* `ANY': ANY, Determine if any values are true
* `ASIN': ASIN, Arcsine function
* `ASINH': ASINH, Inverse hyperbolic sine function
* `ASSOCIATED': ASSOCIATED, Status of a pointer or pointer/target pair
* `ATAN': ATAN, Arctangent function
* `ATAN2': ATAN2, Arctangent function
* `ATANH': ATANH, Inverse hyperbolic tangent function
* `BESSEL_J0': BESSEL_J0, Bessel function of the first kind of order 0
* `BESSEL_J1': BESSEL_J1, Bessel function of the first kind of order 1
* `BESSEL_JN': BESSEL_JN, Bessel function of the first kind
* `BESSEL_Y0': BESSEL_Y0, Bessel function of the second kind of order 0
* `BESSEL_Y1': BESSEL_Y1, Bessel function of the second kind of order 1
* `BESSEL_YN': BESSEL_YN, Bessel function of the second kind
* `BIT_SIZE': BIT_SIZE, Bit size inquiry function
* `BTEST': BTEST, Bit test function
* `C_ASSOCIATED': C_ASSOCIATED, Status of a C pointer
* `C_F_POINTER': C_F_POINTER, Convert C into Fortran pointer
* `C_F_PROCPOINTER': C_F_PROCPOINTER, Convert C into Fortran procedure pointer
* `C_FUNLOC': C_FUNLOC, Obtain the C address of a procedure
* `C_LOC': C_LOC, Obtain the C address of an object
* `C_SIZEOF': C_SIZEOF, Size in bytes of an expression
* `CEILING': CEILING, Integer ceiling function
* `CHAR': CHAR, Integer-to-character conversion function
* `CHDIR': CHDIR, Change working directory
* `CHMOD': CHMOD, Change access permissions of files
* `CMPLX': CMPLX, Complex conversion function
* `COMMAND_ARGUMENT_COUNT': COMMAND_ARGUMENT_COUNT, Get number of command line arguments
* `COMPLEX': COMPLEX, Complex conversion function
* `CONJG': CONJG, Complex conjugate function
* `COS': COS, Cosine function
* `COSH': COSH, Hyperbolic cosine function
* `COUNT': COUNT, Count occurrences of TRUE in an array
* `CPU_TIME': CPU_TIME, CPU time subroutine
* `CSHIFT': CSHIFT, Circular shift elements of an array
* `CTIME': CTIME, Subroutine (or function) to convert a time into a string
* `DATE_AND_TIME': DATE_AND_TIME, Date and time subroutine
* `DBLE': DBLE, Double precision conversion function
* `DCMPLX': DCMPLX, Double complex conversion function
* `DFLOAT': DFLOAT, Double precision conversion function
* `DIGITS': DIGITS, Significant digits function
* `DIM': DIM, Positive difference
* `DOT_PRODUCT': DOT_PRODUCT, Dot product function
* `DPROD': DPROD, Double product function
* `DREAL': DREAL, Double real part function
* `DTIME': DTIME, Execution time subroutine (or function)
* `EOSHIFT': EOSHIFT, End-off shift elements of an array
* `EPSILON': EPSILON, Epsilon function
* `ERF': ERF, Error function
* `ERFC': ERFC, Complementary error function
* `ERFC_SCALED': ERFC_SCALED, Exponentially-scaled complementary error function
* `ETIME': ETIME, Execution time subroutine (or function)
* `EXIT': EXIT, Exit the program with status.
* `EXP': EXP, Exponential function
* `EXPONENT': EXPONENT, Exponent function
* `FDATE': FDATE, Subroutine (or function) to get the current time as a string
* `FGET': FGET, Read a single character in stream mode from stdin
* `FGETC': FGETC, Read a single character in stream mode
* `FLOAT': FLOAT, Convert integer to default real
* `FLOOR': FLOOR, Integer floor function
* `FLUSH': FLUSH, Flush I/O unit(s)
* `FNUM': FNUM, File number function
* `FPUT': FPUT, Write a single character in stream mode to stdout
* `FPUTC': FPUTC, Write a single character in stream mode
* `FRACTION': FRACTION, Fractional part of the model representation
* `FREE': FREE, Memory de-allocation subroutine
* `FSEEK': FSEEK, Low level file positioning subroutine
* `FSTAT': FSTAT, Get file status
* `FTELL': FTELL, Current stream position
* `GAMMA': GAMMA, Gamma function
* `GERROR': GERROR, Get last system error message
* `GETARG': GETARG, Get command line arguments
* `GET_COMMAND': GET_COMMAND, Get the entire command line
* `GET_COMMAND_ARGUMENT': GET_COMMAND_ARGUMENT, Get command line arguments
* `GETCWD': GETCWD, Get current working directory
* `GETENV': GETENV, Get an environmental variable
* `GET_ENVIRONMENT_VARIABLE': GET_ENVIRONMENT_VARIABLE, Get an environmental variable
* `GETGID': GETGID, Group ID function
* `GETLOG': GETLOG, Get login name
* `GETPID': GETPID, Process ID function
* `GETUID': GETUID, User ID function
* `GMTIME': GMTIME, Convert time to GMT info
* `HOSTNM': HOSTNM, Get system host name
* `HUGE': HUGE, Largest number of a kind
* `HYPOT': HYPOT, Euclidian distance function
* `IACHAR': IACHAR, Code in ASCII collating sequence
* `IAND': IAND, Bitwise logical and
* `IARGC': IARGC, Get the number of command line arguments
* `IBCLR': IBCLR, Clear bit
* `IBITS': IBITS, Bit extraction
* `IBSET': IBSET, Set bit
* `ICHAR': ICHAR, Character-to-integer conversion function
* `IDATE': IDATE, Current local time (day/month/year)
* `IEOR': IEOR, Bitwise logical exclusive or
* `IERRNO': IERRNO, Function to get the last system error number
* `INDEX': INDEX intrinsic, Position of a substring within a string
* `INT': INT, Convert to integer type
* `INT2': INT2, Convert to 16-bit integer type
* `INT8': INT8, Convert to 64-bit integer type
* `IOR': IOR, Bitwise logical or
* `IRAND': IRAND, Integer pseudo-random number
* `IS_IOSTAT_END': IS_IOSTAT_END, Test for end-of-file value
* `IS_IOSTAT_EOR': IS_IOSTAT_EOR, Test for end-of-record value
* `ISATTY': ISATTY, Whether a unit is a terminal device
* `ISHFT': ISHFT, Shift bits
* `ISHFTC': ISHFTC, Shift bits circularly
* `ISNAN': ISNAN, Tests for a NaN
* `ITIME': ITIME, Current local time (hour/minutes/seconds)
* `KILL': KILL, Send a signal to a process
* `KIND': KIND, Kind of an entity
* `LBOUND': LBOUND, Lower dimension bounds of an array
* `LEADZ': LEADZ, Number of leading zero bits of an integer
* `LEN': LEN, Length of a character entity
* `LEN_TRIM': LEN_TRIM, Length of a character entity without trailing blank characters
* `LGE': LGE, Lexical greater than or equal
* `LGT': LGT, Lexical greater than
* `LINK': LINK, Create a hard link
* `LLE': LLE, Lexical less than or equal
* `LLT': LLT, Lexical less than
* `LNBLNK': LNBLNK, Index of the last non-blank character in a string
* `LOC': LOC, Returns the address of a variable
* `LOG': LOG, Logarithm function
* `LOG10': LOG10, Base 10 logarithm function
* `LOG_GAMMA': LOG_GAMMA, Logarithm of the Gamma function
* `LOGICAL': LOGICAL, Convert to logical type
* `LONG': LONG, Convert to integer type
* `LSHIFT': LSHIFT, Left shift bits
* `LSTAT': LSTAT, Get file status
* `LTIME': LTIME, Convert time to local time info
* `MALLOC': MALLOC, Dynamic memory allocation function
* `MATMUL': MATMUL, matrix multiplication
* `MAX': MAX, Maximum value of an argument list
* `MAXEXPONENT': MAXEXPONENT, Maximum exponent of a real kind
* `MAXLOC': MAXLOC, Location of the maximum value within an array
* `MAXVAL': MAXVAL, Maximum value of an array
* `MCLOCK': MCLOCK, Time function
* `MCLOCK8': MCLOCK8, Time function (64-bit)
* `MERGE': MERGE, Merge arrays
* `MIN': MIN, Minimum value of an argument list
* `MINEXPONENT': MINEXPONENT, Minimum exponent of a real kind
* `MINLOC': MINLOC, Location of the minimum value within an array
* `MINVAL': MINVAL, Minimum value of an array
* `MOD': MOD, Remainder function
* `MODULO': MODULO, Modulo function
* `MOVE_ALLOC': MOVE_ALLOC, Move allocation from one object to another
* `MVBITS': MVBITS, Move bits from one integer to another
* `NEAREST': NEAREST, Nearest representable number
* `NEW_LINE': NEW_LINE, New line character
* `NINT': NINT, Nearest whole number
* `NOT': NOT, Logical negation
* `NULL': NULL, Function that returns an disassociated pointer
* `OR': OR, Bitwise logical OR
* `PACK': PACK, Pack an array into an array of rank one
* `PERROR': PERROR, Print system error message
* `PRECISION': PRECISION, Decimal precision of a real kind
* `PRESENT': PRESENT, Determine whether an optional dummy argument is specified
* `PRODUCT': PRODUCT, Product of array elements
* `RADIX': RADIX, Base of a data model
* `RANDOM_NUMBER': RANDOM_NUMBER, Pseudo-random number
* `RANDOM_SEED': RANDOM_SEED, Initialize a pseudo-random number sequence
* `RAND': RAND, Real pseudo-random number
* `RANGE': RANGE, Decimal exponent range
* `RAN': RAN, Real pseudo-random number
* `REAL': REAL, Convert to real type
* `RENAME': RENAME, Rename a file
* `REPEAT': REPEAT, Repeated string concatenation
* `RESHAPE': RESHAPE, Function to reshape an array
* `RRSPACING': RRSPACING, Reciprocal of the relative spacing
* `RSHIFT': RSHIFT, Right shift bits
* `SCALE': SCALE, Scale a real value
* `SCAN': SCAN, Scan a string for the presence of a set of characters
* `SECNDS': SECNDS, Time function
* `SECOND': SECOND, CPU time function
* `SELECTED_CHAR_KIND': SELECTED_CHAR_KIND, Choose character kind
* `SELECTED_INT_KIND': SELECTED_INT_KIND, Choose integer kind
* `SELECTED_REAL_KIND': SELECTED_REAL_KIND, Choose real kind
* `SET_EXPONENT': SET_EXPONENT, Set the exponent of the model
* `SHAPE': SHAPE, Determine the shape of an array
* `SIGN': SIGN, Sign copying function
* `SIGNAL': SIGNAL, Signal handling subroutine (or function)
* `SIN': SIN, Sine function
* `SINH': SINH, Hyperbolic sine function
* `SIZE': SIZE, Function to determine the size of an array
* `SIZEOF': SIZEOF, Determine the size in bytes of an expression
* `SLEEP': SLEEP, Sleep for the specified number of seconds
* `SNGL': SNGL, Convert double precision real to default real
* `SPACING': SPACING, Smallest distance between two numbers of a given type
* `SPREAD': SPREAD, Add a dimension to an array
* `SQRT': SQRT, Square-root function
* `SRAND': SRAND, Reinitialize the random number generator
* `STAT': STAT, Get file status
* `SUM': SUM, Sum of array elements
* `SYMLNK': SYMLNK, Create a symbolic link
* `SYSTEM': SYSTEM, Execute a shell command
* `SYSTEM_CLOCK': SYSTEM_CLOCK, Time function
* `TAN': TAN, Tangent function
* `TANH': TANH, Hyperbolic tangent function
* `TIME': TIME, Time function
* `TIME8': TIME8, Time function (64-bit)
* `TINY': TINY, Smallest positive number of a real kind
* `TRAILZ': TRAILZ, Number of trailing zero bits of an integer
* `TRANSFER': TRANSFER, Transfer bit patterns
* `TRANSPOSE': TRANSPOSE, Transpose an array of rank two
* `TRIM': TRIM, Remove trailing blank characters of a string
* `TTYNAM': TTYNAM, Get the name of a terminal device.
* `UBOUND': UBOUND, Upper dimension bounds of an array
* `UMASK': UMASK, Set the file creation mask
* `UNLINK': UNLINK, Remove a file from the file system
* `UNPACK': UNPACK, Unpack an array of rank one into an array
* `VERIFY': VERIFY, Scan a string for the absence of a set of characters
* `XOR': XOR, Bitwise logical exclusive or

File: gfortran.info, Node: Introduction to Intrinsics, Next: ABORT, Up: Intrinsic Procedures
8.1 Introduction to intrinsic procedures
========================================
The intrinsic procedures provided by GNU Fortran include all of the
intrinsic procedures required by the Fortran 95 standard, a set of
intrinsic procedures for backwards compatibility with G77, and a
selection of intrinsic procedures from the Fortran 2003 and Fortran 2008
standards. Any conflict between a description here and a description in
either the Fortran 95 standard, the Fortran 2003 standard or the Fortran
2008 standard is unintentional, and the standard(s) should be considered
authoritative.
The enumeration of the `KIND' type parameter is processor defined in
the Fortran 95 standard. GNU Fortran defines the default integer type
and default real type by `INTEGER(KIND=4)' and `REAL(KIND=4)',
respectively. The standard mandates that both data types shall have
another kind, which have more precision. On typical target
architectures supported by `gfortran', this kind type parameter is
`KIND=8'. Hence, `REAL(KIND=8)' and `DOUBLE PRECISION' are equivalent.
In the description of generic intrinsic procedures, the kind type
parameter will be specified by `KIND=*', and in the description of
specific names for an intrinsic procedure the kind type parameter will
be explicitly given (e.g., `REAL(KIND=4)' or `REAL(KIND=8)'). Finally,
for brevity the optional `KIND=' syntax will be omitted.
Many of the intrinsic procedures take one or more optional arguments.
This document follows the convention used in the Fortran 95 standard,
and denotes such arguments by square brackets.
GNU Fortran offers the `-std=f95' and `-std=gnu' options, which can
be used to restrict the set of intrinsic procedures to a given
standard. By default, `gfortran' sets the `-std=gnu' option, and so
all intrinsic procedures described here are accepted. There is one
caveat. For a select group of intrinsic procedures, `g77' implemented
both a function and a subroutine. Both classes have been implemented
in `gfortran' for backwards compatibility with `g77'. It is noted here
that these functions and subroutines cannot be intermixed in a given
subprogram. In the descriptions that follow, the applicable standard
for each intrinsic procedure is noted.

File: gfortran.info, Node: ABORT, Next: ABS, Prev: Introduction to Intrinsics, Up: Intrinsic Procedures
8.2 `ABORT' -- Abort the program
================================
_Description_:
`ABORT' causes immediate termination of the program. On operating
systems that support a core dump, `ABORT' will produce a core dump
even if the option `-fno-dump-core' is in effect, which is
suitable for debugging purposes.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL ABORT'
_Return value_:
Does not return.
_Example_:
program test_abort
integer :: i = 1, j = 2
if (i /= j) call abort
end program test_abort
_See also_:
*Note EXIT::, *Note KILL::

File: gfortran.info, Node: ABS, Next: ACCESS, Prev: ABORT, Up: Intrinsic Procedures
8.3 `ABS' -- Absolute value
===========================
_Description_:
`ABS(A)' computes the absolute value of `A'.
_Standard_:
Fortran 77 and later, has overloads that are GNU extensions
_Class_:
Elemental function
_Syntax_:
`RESULT = ABS(A)'
_Arguments_:
A The type of the argument shall be an `INTEGER',
`REAL', or `COMPLEX'.
_Return value_:
The return value is of the same type and kind as the argument
except the return value is `REAL' for a `COMPLEX' argument.
_Example_:
program test_abs
integer :: i = -1
real :: x = -1.e0
complex :: z = (-1.e0,0.e0)
i = abs(i)
x = abs(x)
x = abs(z)
end program test_abs
_Specific names_:
Name Argument Return type Standard
`CABS(A)' `COMPLEX(4) `REAL(4)' Fortran 77 and
Z' later
`DABS(A)' `REAL(8) `REAL(8)' Fortran 77 and
X' later
`IABS(A)' `INTEGER(4) `INTEGER(4)' Fortran 77 and
I' later
`ZABS(A)' `COMPLEX(8) `COMPLEX(8)' GNU extension
Z'
`CDABS(A)' `COMPLEX(8) `COMPLEX(8)' GNU extension
Z'

File: gfortran.info, Node: ACCESS, Next: ACHAR, Prev: ABS, Up: Intrinsic Procedures
8.4 `ACCESS' -- Checks file access modes
========================================
_Description_:
`ACCESS(NAME, MODE)' checks whether the file NAME exists, is
readable, writable or executable. Except for the executable check,
`ACCESS' can be replaced by Fortran 95's `INQUIRE'.
_Standard_:
GNU extension
_Class_:
Inquiry function
_Syntax_:
`RESULT = ACCESS(NAME, MODE)'
_Arguments_:
NAME Scalar `CHARACTER' of default kind with the
file name. Tailing blank are ignored unless
the character `achar(0)' is present, then all
characters up to and excluding `achar(0)' are
used as file name.
MODE Scalar `CHARACTER' of default kind with the
file access mode, may be any concatenation of
`"r"' (readable), `"w"' (writable) and `"x"'
(executable), or `" "' to check for existence.
_Return value_:
Returns a scalar `INTEGER', which is `0' if the file is accessible
in the given mode; otherwise or if an invalid argument has been
given for `MODE' the value `1' is returned.
_Example_:
program access_test
implicit none
character(len=*), parameter :: file = 'test.dat'
character(len=*), parameter :: file2 = 'test.dat '//achar(0)
if(access(file,' ') == 0) print *, trim(file),' is exists'
if(access(file,'r') == 0) print *, trim(file),' is readable'
if(access(file,'w') == 0) print *, trim(file),' is writable'
if(access(file,'x') == 0) print *, trim(file),' is executable'
if(access(file2,'rwx') == 0) &
print *, trim(file2),' is readable, writable and executable'
end program access_test
_Specific names_:
_See also_:

File: gfortran.info, Node: ACHAR, Next: ACOS, Prev: ACCESS, Up: Intrinsic Procedures
8.5 `ACHAR' -- Character in ASCII collating sequence
====================================================
_Description_:
`ACHAR(I)' returns the character located at position `I' in the
ASCII collating sequence.
_Standard_:
Fortran 77 and later, with KIND argument Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ACHAR(I [, KIND])'
_Arguments_:
I The type shall be `INTEGER'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `CHARACTER' with a length of one. If
the KIND argument is present, the return value is of the specified
kind and of the default kind otherwise.
_Example_:
program test_achar
character c
c = achar(32)
end program test_achar
_Note_:
See *Note ICHAR:: for a discussion of converting between numerical
values and formatted string representations.
_See also_:
*Note CHAR::, *Note IACHAR::, *Note ICHAR::

File: gfortran.info, Node: ACOS, Next: ACOSH, Prev: ACHAR, Up: Intrinsic Procedures
8.6 `ACOS' -- Arccosine function
================================
_Description_:
`ACOS(X)' computes the arccosine of X (inverse of `COS(X)').
_Standard_:
Fortran 77 and later, for a complex argument Fortran 2008 or later
_Class_:
Elemental function
_Syntax_:
`RESULT = ACOS(X)'
_Arguments_:
X The type shall either be `REAL' with a
magnitude that is less than or equal to one -
or the type shall be `COMPLEX'.
_Return value_:
The return value is of the same type and kind as X. The real part
of the result is in radians and lies in the range 0 \leq \Re
\acos(x) \leq \pi.
_Example_:
program test_acos
real(8) :: x = 0.866_8
x = acos(x)
end program test_acos
_Specific names_:
Name Argument Return type Standard
`DACOS(X)' `REAL(8) X' `REAL(8)' Fortran 77 and
later
_See also_:
Inverse function: *Note COS::

File: gfortran.info, Node: ACOSH, Next: ADJUSTL, Prev: ACOS, Up: Intrinsic Procedures
8.7 `ACOSH' -- Inverse hyperbolic cosine function
=================================================
_Description_:
`ACOSH(X)' computes the inverse hyperbolic cosine of X.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ACOSH(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has the same type and kind as X. If X is complex,
the imaginary part of the result is in radians and lies between 0
\leq \Im \acosh(x) \leq \pi.
_Example_:
PROGRAM test_acosh
REAL(8), DIMENSION(3) :: x = (/ 1.0, 2.0, 3.0 /)
WRITE (*,*) ACOSH(x)
END PROGRAM
_Specific names_:
Name Argument Return type Standard
`DACOSH(X)' `REAL(8) X' `REAL(8)' GNU extension
_See also_:
Inverse function: *Note COSH::

File: gfortran.info, Node: ADJUSTL, Next: ADJUSTR, Prev: ACOSH, Up: Intrinsic Procedures
8.8 `ADJUSTL' -- Left adjust a string
=====================================
_Description_:
`ADJUSTL(STRING)' will left adjust a string by removing leading
spaces. Spaces are inserted at the end of the string as needed.
_Standard_:
Fortran 90 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ADJUSTL(STRING)'
_Arguments_:
STRING The type shall be `CHARACTER'.
_Return value_:
The return value is of type `CHARACTER' and of the same kind as
STRING where leading spaces are removed and the same number of
spaces are inserted on the end of STRING.
_Example_:
program test_adjustl
character(len=20) :: str = ' gfortran'
str = adjustl(str)
print *, str
end program test_adjustl
_See also_:
*Note ADJUSTR::, *Note TRIM::

File: gfortran.info, Node: ADJUSTR, Next: AIMAG, Prev: ADJUSTL, Up: Intrinsic Procedures
8.9 `ADJUSTR' -- Right adjust a string
======================================
_Description_:
`ADJUSTR(STRING)' will right adjust a string by removing trailing
spaces. Spaces are inserted at the start of the string as needed.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ADJUSTR(STRING)'
_Arguments_:
STR The type shall be `CHARACTER'.
_Return value_:
The return value is of type `CHARACTER' and of the same kind as
STRING where trailing spaces are removed and the same number of
spaces are inserted at the start of STRING.
_Example_:
program test_adjustr
character(len=20) :: str = 'gfortran'
str = adjustr(str)
print *, str
end program test_adjustr
_See also_:
*Note ADJUSTL::, *Note TRIM::

File: gfortran.info, Node: AIMAG, Next: AINT, Prev: ADJUSTR, Up: Intrinsic Procedures
8.10 `AIMAG' -- Imaginary part of complex number
================================================
_Description_:
`AIMAG(Z)' yields the imaginary part of complex argument `Z'. The
`IMAG(Z)' and `IMAGPART(Z)' intrinsic functions are provided for
compatibility with `g77', and their use in new code is strongly
discouraged.
_Standard_:
Fortran 77 and later, has overloads that are GNU extensions
_Class_:
Elemental function
_Syntax_:
`RESULT = AIMAG(Z)'
_Arguments_:
Z The type of the argument shall be `COMPLEX'.
_Return value_:
The return value is of type `REAL' with the kind type parameter of
the argument.
_Example_:
program test_aimag
complex(4) z4
complex(8) z8
z4 = cmplx(1.e0_4, 0.e0_4)
z8 = cmplx(0.e0_8, 1.e0_8)
print *, aimag(z4), dimag(z8)
end program test_aimag
_Specific names_:
Name Argument Return type Standard
`DIMAG(Z)' `COMPLEX(8) `REAL(8)' GNU extension
Z'
`IMAG(Z)' `COMPLEX Z' `REAL' GNU extension
`IMAGPART(Z)' `COMPLEX Z' `REAL' GNU extension

File: gfortran.info, Node: AINT, Next: ALARM, Prev: AIMAG, Up: Intrinsic Procedures
8.11 `AINT' -- Truncate to a whole number
=========================================
_Description_:
`AINT(A [, KIND])' truncates its argument to a whole number.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = AINT(A [, KIND])'
_Arguments_:
A The type of the argument shall be `REAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `REAL' with the kind type parameter of
the argument if the optional KIND is absent; otherwise, the kind
type parameter will be given by KIND. If the magnitude of X is
less than one, `AINT(X)' returns zero. If the magnitude is equal
to or greater than one then it returns the largest whole number
that does not exceed its magnitude. The sign is the same as the
sign of X.
_Example_:
program test_aint
real(4) x4
real(8) x8
x4 = 1.234E0_4
x8 = 4.321_8
print *, aint(x4), dint(x8)
x8 = aint(x4,8)
end program test_aint
_Specific names_:
Name Argument Return type Standard
`DINT(X)' `REAL(8) X' `REAL(8)' Fortran 77 and
later

File: gfortran.info, Node: ALARM, Next: ALL, Prev: AINT, Up: Intrinsic Procedures
8.12 `ALARM' -- Execute a routine after a given delay
=====================================================
_Description_:
`ALARM(SECONDS, HANDLER [, STATUS])' causes external subroutine
HANDLER to be executed after a delay of SECONDS by using
`alarm(2)' to set up a signal and `signal(2)' to catch it. If
STATUS is supplied, it will be returned with the number of seconds
remaining until any previously scheduled alarm was due to be
delivered, or zero if there was no previously scheduled alarm.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL ALARM(SECONDS, HANDLER [, STATUS])'
_Arguments_:
SECONDS The type of the argument shall be a scalar
`INTEGER'. It is `INTENT(IN)'.
HANDLER Signal handler (`INTEGER FUNCTION' or
`SUBROUTINE') or dummy/global `INTEGER'
scalar. The scalar values may be either
`SIG_IGN=1' to ignore the alarm generated or
`SIG_DFL=0' to set the default action. It is
`INTENT(IN)'.
STATUS (Optional) STATUS shall be a scalar variable
of the default `INTEGER' kind. It is
`INTENT(OUT)'.
_Example_:
program test_alarm
external handler_print
integer i
call alarm (3, handler_print, i)
print *, i
call sleep(10)
end program test_alarm
This will cause the external routine HANDLER_PRINT to be called
after 3 seconds.

File: gfortran.info, Node: ALL, Next: ALLOCATED, Prev: ALARM, Up: Intrinsic Procedures
8.13 `ALL' -- All values in MASK along DIM are true
===================================================
_Description_:
`ALL(MASK [, DIM])' determines if all the values are true in MASK
in the array along dimension DIM.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = ALL(MASK [, DIM])'
_Arguments_:
MASK The type of the argument shall be `LOGICAL' and
it shall not be scalar.
DIM (Optional) DIM shall be a scalar integer with
a value that lies between one and the rank of
MASK.
_Return value_:
`ALL(MASK)' returns a scalar value of type `LOGICAL' where the
kind type parameter is the same as the kind type parameter of
MASK. If DIM is present, then `ALL(MASK, DIM)' returns an array
with the rank of MASK minus 1. The shape is determined from the
shape of MASK where the DIM dimension is elided.
(A)
`ALL(MASK)' is true if all elements of MASK are true. It
also is true if MASK has zero size; otherwise, it is false.
(B)
If the rank of MASK is one, then `ALL(MASK,DIM)' is equivalent
to `ALL(MASK)'. If the rank is greater than one, then
`ALL(MASK,DIM)' is determined by applying `ALL' to the array
sections.
_Example_:
program test_all
logical l
l = all((/.true., .true., .true./))
print *, l
call section
contains
subroutine section
integer a(2,3), b(2,3)
a = 1
b = 1
b(2,2) = 2
print *, all(a .eq. b, 1)
print *, all(a .eq. b, 2)
end subroutine section
end program test_all

File: gfortran.info, Node: ALLOCATED, Next: AND, Prev: ALL, Up: Intrinsic Procedures
8.14 `ALLOCATED' -- Status of an allocatable entity
===================================================
_Description_:
`ALLOCATED(ARRAY)' checks the status of whether X is allocated.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = ALLOCATED(ARRAY)'
_Arguments_:
ARRAY The argument shall be an `ALLOCATABLE' array.
_Return value_:
The return value is a scalar `LOGICAL' with the default logical
kind type parameter. If ARRAY is allocated, `ALLOCATED(ARRAY)' is
`.TRUE.'; otherwise, it returns `.FALSE.'
_Example_:
program test_allocated
integer :: i = 4
real(4), allocatable :: x(:)
if (.not. allocated(x)) allocate(x(i))
end program test_allocated

File: gfortran.info, Node: AND, Next: ANINT, Prev: ALLOCATED, Up: Intrinsic Procedures
8.15 `AND' -- Bitwise logical AND
=================================
_Description_:
Bitwise logical `AND'.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. For integer arguments, programmers should consider
the use of the *Note IAND:: intrinsic defined by the Fortran
standard.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = AND(I, J)'
_Arguments_:
I The type shall be either a scalar `INTEGER'
type or a scalar `LOGICAL' type.
J The type shall be the same as the type of I.
_Return value_:
The return type is either a scalar `INTEGER' or a scalar
`LOGICAL'. If the kind type parameters differ, then the smaller
kind type is implicitly converted to larger kind, and the return
has the larger kind.
_Example_:
PROGRAM test_and
LOGICAL :: T = .TRUE., F = .FALSE.
INTEGER :: a, b
DATA a / Z'F' /, b / Z'3' /
WRITE (*,*) AND(T, T), AND(T, F), AND(F, T), AND(F, F)
WRITE (*,*) AND(a, b)
END PROGRAM
_See also_:
Fortran 95 elemental function: *Note IAND::

File: gfortran.info, Node: ANINT, Next: ANY, Prev: AND, Up: Intrinsic Procedures
8.16 `ANINT' -- Nearest whole number
====================================
_Description_:
`ANINT(A [, KIND])' rounds its argument to the nearest whole
number.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ANINT(A [, KIND])'
_Arguments_:
A The type of the argument shall be `REAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type real with the kind type parameter of
the argument if the optional KIND is absent; otherwise, the kind
type parameter will be given by KIND. If A is greater than zero,
`ANINT(A)' returns `AINT(X+0.5)'. If A is less than or equal to
zero then it returns `AINT(X-0.5)'.
_Example_:
program test_anint
real(4) x4
real(8) x8
x4 = 1.234E0_4
x8 = 4.321_8
print *, anint(x4), dnint(x8)
x8 = anint(x4,8)
end program test_anint
_Specific names_:
Name Argument Return type Standard
`DNINT(A)' `REAL(8) A' `REAL(8)' Fortran 77 and
later

File: gfortran.info, Node: ANY, Next: ASIN, Prev: ANINT, Up: Intrinsic Procedures
8.17 `ANY' -- Any value in MASK along DIM is true
=================================================
_Description_:
`ANY(MASK [, DIM])' determines if any of the values in the logical
array MASK along dimension DIM are `.TRUE.'.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = ANY(MASK [, DIM])'
_Arguments_:
MASK The type of the argument shall be `LOGICAL' and
it shall not be scalar.
DIM (Optional) DIM shall be a scalar integer with
a value that lies between one and the rank of
MASK.
_Return value_:
`ANY(MASK)' returns a scalar value of type `LOGICAL' where the
kind type parameter is the same as the kind type parameter of
MASK. If DIM is present, then `ANY(MASK, DIM)' returns an array
with the rank of MASK minus 1. The shape is determined from the
shape of MASK where the DIM dimension is elided.
(A)
`ANY(MASK)' is true if any element of MASK is true;
otherwise, it is false. It also is false if MASK has zero
size.
(B)
If the rank of MASK is one, then `ANY(MASK,DIM)' is equivalent
to `ANY(MASK)'. If the rank is greater than one, then
`ANY(MASK,DIM)' is determined by applying `ANY' to the array
sections.
_Example_:
program test_any
logical l
l = any((/.true., .true., .true./))
print *, l
call section
contains
subroutine section
integer a(2,3), b(2,3)
a = 1
b = 1
b(2,2) = 2
print *, any(a .eq. b, 1)
print *, any(a .eq. b, 2)
end subroutine section
end program test_any

File: gfortran.info, Node: ASIN, Next: ASINH, Prev: ANY, Up: Intrinsic Procedures
8.18 `ASIN' -- Arcsine function
===============================
_Description_:
`ASIN(X)' computes the arcsine of its X (inverse of `SIN(X)').
_Standard_:
Fortran 77 and later, for a complex argument Fortran 2008 or later
_Class_:
Elemental function
_Syntax_:
`RESULT = ASIN(X)'
_Arguments_:
X The type shall be either `REAL' and a
magnitude that is less than or equal to one -
or be `COMPLEX'.
_Return value_:
The return value is of the same type and kind as X. The real part
of the result is in radians and lies in the range -\pi/2 \leq \Re
\asin(x) \leq \pi/2.
_Example_:
program test_asin
real(8) :: x = 0.866_8
x = asin(x)
end program test_asin
_Specific names_:
Name Argument Return type Standard
`DASIN(X)' `REAL(8) X' `REAL(8)' Fortran 77 and
later
_See also_:
Inverse function: *Note SIN::

File: gfortran.info, Node: ASINH, Next: ASSOCIATED, Prev: ASIN, Up: Intrinsic Procedures
8.19 `ASINH' -- Inverse hyperbolic sine function
================================================
_Description_:
`ASINH(X)' computes the inverse hyperbolic sine of X.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ASINH(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value is of the same type and kind as X. If X is
complex, the imaginary part of the result is in radians and lies
between -\pi/2 \leq \Im \asinh(x) \leq \pi/2.
_Example_:
PROGRAM test_asinh
REAL(8), DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /)
WRITE (*,*) ASINH(x)
END PROGRAM
_Specific names_:
Name Argument Return type Standard
`DASINH(X)' `REAL(8) X' `REAL(8)' GNU extension.
_See also_:
Inverse function: *Note SINH::

File: gfortran.info, Node: ASSOCIATED, Next: ATAN, Prev: ASINH, Up: Intrinsic Procedures
8.20 `ASSOCIATED' -- Status of a pointer or pointer/target pair
===============================================================
_Description_:
`ASSOCIATED(POINTER [, TARGET])' determines the status of the
pointer POINTER or if POINTER is associated with the target TARGET.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = ASSOCIATED(POINTER [, TARGET])'
_Arguments_:
POINTER POINTER shall have the `POINTER' attribute and
it can be of any type.
TARGET (Optional) TARGET shall be a pointer or a
target. It must have the same type, kind type
parameter, and array rank as POINTER.
The association status of neither POINTER nor TARGET shall be
undefined.
_Return value_:
`ASSOCIATED(POINTER)' returns a scalar value of type `LOGICAL(4)'.
There are several cases:
(A) When the optional TARGET is not present then
`ASSOCIATED(POINTER)' is true if POINTER is associated with a
target; otherwise, it returns false.
(B) If TARGET is present and a scalar target, the result is true if
TARGET is not a zero-sized storage sequence and the target
associated with POINTER occupies the same storage units. If
POINTER is disassociated, the result is false.
(C) If TARGET is present and an array target, the result is true if
TARGET and POINTER have the same shape, are not zero-sized
arrays, are arrays whose elements are not zero-sized storage
sequences, and TARGET and POINTER occupy the same storage
units in array element order. As in case(B), the result is
false, if POINTER is disassociated.
(D) If TARGET is present and an scalar pointer, the result is true
if TARGET is associated with POINTER, the target associated
with TARGET are not zero-sized storage sequences and occupy
the same storage units. The result is false, if either
TARGET or POINTER is disassociated.
(E) If TARGET is present and an array pointer, the result is true if
target associated with POINTER and the target associated with
TARGET have the same shape, are not zero-sized arrays, are
arrays whose elements are not zero-sized storage sequences,
and TARGET and POINTER occupy the same storage units in array
element order. The result is false, if either TARGET or
POINTER is disassociated.
_Example_:
program test_associated
implicit none
real, target :: tgt(2) = (/1., 2./)
real, pointer :: ptr(:)
ptr => tgt
if (associated(ptr) .eqv. .false.) call abort
if (associated(ptr,tgt) .eqv. .false.) call abort
end program test_associated
_See also_:
*Note NULL::

File: gfortran.info, Node: ATAN, Next: ATAN2, Prev: ASSOCIATED, Up: Intrinsic Procedures
8.21 `ATAN' -- Arctangent function
==================================
_Description_:
`ATAN(X)' computes the arctangent of X.
_Standard_:
Fortran 77 and later, for a complex argument and for two arguments
Fortran 2008 or later
_Class_:
Elemental function
_Syntax_:
`RESULT = ATAN(X)' `RESULT = ATAN(Y, X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'; if Y is
present, X shall be REAL.
Y shall
be of the
same type
and kind
as X.
_Return value_:
The return value is of the same type and kind as X. If Y is
present, the result is identical to `ATAN2(Y,X)'. Otherwise, it
the arcus tangent of X, where the real part of the result is in
radians and lies in the range -\pi/2 \leq \Re \atan(x) \leq \pi/2.
_Example_:
program test_atan
real(8) :: x = 2.866_8
x = atan(x)
end program test_atan
_Specific names_:
Name Argument Return type Standard
`DATAN(X)' `REAL(8) X' `REAL(8)' Fortran 77 and
later
_See also_:
Inverse function: *Note TAN::

File: gfortran.info, Node: ATAN2, Next: ATANH, Prev: ATAN, Up: Intrinsic Procedures
8.22 `ATAN2' -- Arctangent function
===================================
_Description_:
`ATAN2(Y, X)' computes the principal value of the argument
function of the complex number X + i Y. This function can be used
to transform from carthesian into polar coordinates and allows to
determine the angle in the correct quadrant.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ATAN2(Y, X)'
_Arguments_:
Y The type shall be `REAL'.
X The type and kind type parameter shall be the
same as Y. If Y is zero, then X must be
nonzero.
_Return value_:
The return value has the same type and kind type parameter as Y.
It is the principal value of the complex number X + i Y. If X is
nonzero, then it lies in the range -\pi \le \atan (x) \leq \pi.
The sign is positive if Y is positive. If Y is zero, then the
return value is zero if X is positive and \pi if X is negative.
Finally, if X is zero, then the magnitude of the result is \pi/2.
_Example_:
program test_atan2
real(4) :: x = 1.e0_4, y = 0.5e0_4
x = atan2(y,x)
end program test_atan2
_Specific names_:
Name Argument Return type Standard
`DATAN2(X, `REAL(8) X', `REAL(8)' Fortran 77 and
Y)' `REAL(8) Y' later

File: gfortran.info, Node: ATANH, Next: BESSEL_J0, Prev: ATAN2, Up: Intrinsic Procedures
8.23 `ATANH' -- Inverse hyperbolic tangent function
===================================================
_Description_:
`ATANH(X)' computes the inverse hyperbolic tangent of X.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ATANH(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has same type and kind as X. If X is complex, the
imaginary part of the result is in radians and lies between -\pi/2
\leq \Im \atanh(x) \leq \pi/2.
_Example_:
PROGRAM test_atanh
REAL, DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /)
WRITE (*,*) ATANH(x)
END PROGRAM
_Specific names_:
Name Argument Return type Standard
`DATANH(X)' `REAL(8) X' `REAL(8)' GNU extension
_See also_:
Inverse function: *Note TANH::

File: gfortran.info, Node: BESSEL_J0, Next: BESSEL_J1, Prev: ATANH, Up: Intrinsic Procedures
8.24 `BESSEL_J0' -- Bessel function of the first kind of order 0
================================================================
_Description_:
`BESSEL_J0(X)' computes the Bessel function of the first kind of
order 0 of X. This function is available under the name `BESJ0' as
a GNU extension.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = BESSEL_J0(X)'
_Arguments_:
X The type shall be `REAL', and it shall be
scalar.
_Return value_:
The return value is of type `REAL' and lies in the range -
0.4027... \leq Bessel (0,x) \leq 1. It has the same kind as X.
_Example_:
program test_besj0
real(8) :: x = 0.0_8
x = bessel_j0(x)
end program test_besj0
_Specific names_:
Name Argument Return type Standard
`DBESJ0(X)' `REAL(8) X' `REAL(8)' GNU extension

File: gfortran.info, Node: BESSEL_J1, Next: BESSEL_JN, Prev: BESSEL_J0, Up: Intrinsic Procedures
8.25 `BESSEL_J1' -- Bessel function of the first kind of order 1
================================================================
_Description_:
`BESSEL_J1(X)' computes the Bessel function of the first kind of
order 1 of X. This function is available under the name `BESJ1' as
a GNU extension.
_Standard_:
Fortran 2008
_Class_:
Elemental function
_Syntax_:
`RESULT = BESSEL_J1(X)'
_Arguments_:
X The type shall be `REAL', and it shall be
scalar.
_Return value_:
The return value is of type `REAL' and it lies in the range -
0.5818... \leq Bessel (0,x) \leq 0.5818 . It has the same kind as
X.
_Example_:
program test_besj1
real(8) :: x = 1.0_8
x = bessel_j1(x)
end program test_besj1
_Specific names_:
Name Argument Return type Standard
`DBESJ1(X)' `REAL(8) X' `REAL(8)' GNU extension

File: gfortran.info, Node: BESSEL_JN, Next: BESSEL_Y0, Prev: BESSEL_J1, Up: Intrinsic Procedures
8.26 `BESSEL_JN' -- Bessel function of the first kind
=====================================================
_Description_:
`BESSEL_JN(N, X)' computes the Bessel function of the first kind of
order N of X. This function is available under the name `BESJN' as
a GNU extension.
If both arguments are arrays, their ranks and shapes shall conform.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = BESSEL_JN(N, X)'
_Arguments_:
N Shall be a scalar or an array of type
`INTEGER'.
X Shall be a scalar or an array of type `REAL'.
_Return value_:
The return value is a scalar of type `REAL'. It has the same kind
as X.
_Example_:
program test_besjn
real(8) :: x = 1.0_8
x = bessel_jn(5,x)
end program test_besjn
_Specific names_:
Name Argument Return type Standard
`DBESJN(N, `INTEGER N' `REAL(8)' GNU extension
X)'
`REAL(8) X'

File: gfortran.info, Node: BESSEL_Y0, Next: BESSEL_Y1, Prev: BESSEL_JN, Up: Intrinsic Procedures
8.27 `BESSEL_Y0' -- Bessel function of the second kind of order 0
=================================================================
_Description_:
`BESSEL_Y0(X)' computes the Bessel function of the second kind of
order 0 of X. This function is available under the name `BESY0' as
a GNU extension.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = BESSEL_Y0(X)'
_Arguments_:
X The type shall be `REAL', and it shall be
scalar.
_Return value_:
The return value is a scalar of type `REAL'. It has the same kind
as X.
_Example_:
program test_besy0
real(8) :: x = 0.0_8
x = bessel_y0(x)
end program test_besy0
_Specific names_:
Name Argument Return type Standard
`DBESY0(X)' `REAL(8) X' `REAL(8)' GNU extension

File: gfortran.info, Node: BESSEL_Y1, Next: BESSEL_YN, Prev: BESSEL_Y0, Up: Intrinsic Procedures
8.28 `BESSEL_Y1' -- Bessel function of the second kind of order 1
=================================================================
_Description_:
`BESSEL_Y1(X)' computes the Bessel function of the second kind of
order 1 of X. This function is available under the name `BESY1' as
a GNU extension.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = BESSEL_Y1(X)'
_Arguments_:
X The type shall be `REAL', and it shall be
scalar.
_Return value_:
The return value is a scalar of type `REAL'. It has the same kind
as X.
_Example_:
program test_besy1
real(8) :: x = 1.0_8
x = bessel_y1(x)
end program test_besy1
_Specific names_:
Name Argument Return type Standard
`DBESY1(X)' `REAL(8) X' `REAL(8)' GNU extension

File: gfortran.info, Node: BESSEL_YN, Next: BIT_SIZE, Prev: BESSEL_Y1, Up: Intrinsic Procedures
8.29 `BESSEL_YN' -- Bessel function of the second kind
======================================================
_Description_:
`BESSEL_YN(N, X)' computes the Bessel function of the second kind
of order N of X. This function is available under the name `BESYN'
as a GNU extension.
If both arguments are arrays, their ranks and shapes shall conform.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = BESSEL_YN(N, X)'
_Arguments_:
N Shall be a scalar or an array of type
`INTEGER'.
X Shall be a scalar or an array of type `REAL'.
_Return value_:
The return value is a scalar of type `REAL'. It has the same kind
as X.
_Example_:
program test_besyn
real(8) :: x = 1.0_8
x = bessel_yn(5,x)
end program test_besyn
_Specific names_:
Name Argument Return type Standard
`DBESYN(N,X)' `INTEGER N' `REAL(8)' GNU extension
`REAL(8)
X'

File: gfortran.info, Node: BIT_SIZE, Next: BTEST, Prev: BESSEL_YN, Up: Intrinsic Procedures
8.30 `BIT_SIZE' -- Bit size inquiry function
============================================
_Description_:
`BIT_SIZE(I)' returns the number of bits (integer precision plus
sign bit) represented by the type of I. The result of
`BIT_SIZE(I)' is independent of the actual value of I.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = BIT_SIZE(I)'
_Arguments_:
I The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER'
_Example_:
program test_bit_size
integer :: i = 123
integer :: size
size = bit_size(i)
print *, size
end program test_bit_size

File: gfortran.info, Node: BTEST, Next: C_ASSOCIATED, Prev: BIT_SIZE, Up: Intrinsic Procedures
8.31 `BTEST' -- Bit test function
=================================
_Description_:
`BTEST(I,POS)' returns logical `.TRUE.' if the bit at POS in I is
set. The counting of the bits starts at 0.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = BTEST(I, POS)'
_Arguments_:
I The type shall be `INTEGER'.
POS The type shall be `INTEGER'.
_Return value_:
The return value is of type `LOGICAL'
_Example_:
program test_btest
integer :: i = 32768 + 1024 + 64
integer :: pos
logical :: bool
do pos=0,16
bool = btest(i, pos)
print *, pos, bool
end do
end program test_btest

File: gfortran.info, Node: C_ASSOCIATED, Next: C_F_POINTER, Prev: BTEST, Up: Intrinsic Procedures
8.32 `C_ASSOCIATED' -- Status of a C pointer
============================================
_Description_:
`C_ASSOCIATED(c_prt_1[, c_ptr_2])' determines the status of the C
pointer C_PTR_1 or if C_PTR_1 is associated with the target
C_PTR_2.
_Standard_:
Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = C_ASSOCIATED(c_prt_1[, c_ptr_2])'
_Arguments_:
C_PTR_1 Scalar of the type `C_PTR' or `C_FUNPTR'.
C_PTR_2 (Optional) Scalar of the same type as C_PTR_1.
_Return value_:
The return value is of type `LOGICAL'; it is `.false.' if either
C_PTR_1 is a C NULL pointer or if C_PTR1 and C_PTR_2 point to
different addresses.
_Example_:
subroutine association_test(a,b)
use iso_c_binding, only: c_associated, c_loc, c_ptr
implicit none
real, pointer :: a
type(c_ptr) :: b
if(c_associated(b, c_loc(a))) &
stop 'b and a do not point to same target'
end subroutine association_test
_See also_:
*Note C_LOC::, *Note C_FUNLOC::

File: gfortran.info, Node: C_FUNLOC, Next: C_LOC, Prev: C_F_PROCPOINTER, Up: Intrinsic Procedures
8.33 `C_FUNLOC' -- Obtain the C address of a procedure
======================================================
_Description_:
`C_FUNLOC(x)' determines the C address of the argument.
_Standard_:
Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = C_FUNLOC(x)'
_Arguments_:
X Interoperable function or pointer to such
function.
_Return value_:
The return value is of type `C_FUNPTR' and contains the C address
of the argument.
_Example_:
module x
use iso_c_binding
implicit none
contains
subroutine sub(a) bind(c)
real(c_float) :: a
a = sqrt(a)+5.0
end subroutine sub
end module x
program main
use iso_c_binding
use x
implicit none
interface
subroutine my_routine(p) bind(c,name='myC_func')
import :: c_funptr
type(c_funptr), intent(in) :: p
end subroutine
end interface
call my_routine(c_funloc(sub))
end program main
_See also_:
*Note C_ASSOCIATED::, *Note C_LOC::, *Note C_F_POINTER::, *Note
C_F_PROCPOINTER::

File: gfortran.info, Node: C_F_PROCPOINTER, Next: C_FUNLOC, Prev: C_F_POINTER, Up: Intrinsic Procedures
8.34 `C_F_PROCPOINTER' -- Convert C into Fortran procedure pointer
==================================================================
_Description_:
`C_F_PROCPOINTER(CPTR, FPTR)' Assign the target of the C function
pointer CPTR to the Fortran procedure pointer FPTR.
_Standard_:
Fortran 2003 and later
_Class_:
Subroutine
_Syntax_:
`CALL C_F_PROCPOINTER(cptr, fptr)'
_Arguments_:
CPTR scalar of the type `C_FUNPTR'. It is
`INTENT(IN)'.
FPTR procedure pointer interoperable with CPTR. It
is `INTENT(OUT)'.
_Example_:
program main
use iso_c_binding
implicit none
abstract interface
function func(a)
import :: c_float
real(c_float), intent(in) :: a
real(c_float) :: func
end function
end interface
interface
function getIterFunc() bind(c,name="getIterFunc")
import :: c_funptr
type(c_funptr) :: getIterFunc
end function
end interface
type(c_funptr) :: cfunptr
procedure(func), pointer :: myFunc
cfunptr = getIterFunc()
call c_f_procpointer(cfunptr, myFunc)
end program main
_See also_:
*Note C_LOC::, *Note C_F_POINTER::

File: gfortran.info, Node: C_F_POINTER, Next: C_F_PROCPOINTER, Prev: C_ASSOCIATED, Up: Intrinsic Procedures
8.35 `C_F_POINTER' -- Convert C into Fortran pointer
====================================================
_Description_:
`C_F_POINTER(CPTR, FPTR[, SHAPE])' Assign the target the C pointer
CPTR to the Fortran pointer FPTR and specify its shape.
_Standard_:
Fortran 2003 and later
_Class_:
Subroutine
_Syntax_:
`CALL C_F_POINTER(CPTR, FPTR[, SHAPE])'
_Arguments_:
CPTR scalar of the type `C_PTR'. It is `INTENT(IN)'.
FPTR pointer interoperable with CPTR. It is
`INTENT(OUT)'.
SHAPE (Optional) Rank-one array of type `INTEGER'
with `INTENT(IN)'. It shall be present if and
only if FPTR is an array. The size must be
equal to the rank of FPTR.
_Example_:
program main
use iso_c_binding
implicit none
interface
subroutine my_routine(p) bind(c,name='myC_func')
import :: c_ptr
type(c_ptr), intent(out) :: p
end subroutine
end interface
type(c_ptr) :: cptr
real,pointer :: a(:)
call my_routine(cptr)
call c_f_pointer(cptr, a, [12])
end program main
_See also_:
*Note C_LOC::, *Note C_F_PROCPOINTER::

File: gfortran.info, Node: C_LOC, Next: C_SIZEOF, Prev: C_FUNLOC, Up: Intrinsic Procedures
8.36 `C_LOC' -- Obtain the C address of an object
=================================================
_Description_:
`C_LOC(X)' determines the C address of the argument.
_Standard_:
Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = C_LOC(X)'
_Arguments_:
X Associated scalar pointer or interoperable
scalar or allocated allocatable variable with
`TARGET' attribute.
_Return value_:
The return value is of type `C_PTR' and contains the C address of
the argument.
_Example_:
subroutine association_test(a,b)
use iso_c_binding, only: c_associated, c_loc, c_ptr
implicit none
real, pointer :: a
type(c_ptr) :: b
if(c_associated(b, c_loc(a))) &
stop 'b and a do not point to same target'
end subroutine association_test
_See also_:
*Note C_ASSOCIATED::, *Note C_FUNLOC::, *Note C_F_POINTER::, *Note
C_F_PROCPOINTER::

File: gfortran.info, Node: C_SIZEOF, Next: CEILING, Prev: C_LOC, Up: Intrinsic Procedures
8.37 `C_SIZEOF' -- Size in bytes of an expression
=================================================
_Description_:
`C_SIZEOF(X)' calculates the number of bytes of storage the
expression `X' occupies.
_Standard_:
Fortran 2008
_Class_:
Intrinsic function
_Syntax_:
`N = C_SIZEOF(X)'
_Arguments_:
X The argument shall be of any type, rank or
shape.
_Return value_:
The return value is of type integer and of the system-dependent
kind C_SIZE_T (from the ISO_C_BINDING module). Its value is the
number of bytes occupied by the argument. If the argument has the
`POINTER' attribute, the number of bytes of the storage area
pointed to is returned. If the argument is of a derived type with
`POINTER' or `ALLOCATABLE' components, the return value doesn't
account for the sizes of the data pointed to by these components.
_Example_:
use iso_c_binding
integer(c_int) :: i
real(c_float) :: r, s(5)
print *, (c_sizeof(s)/c_sizeof(r) == 5)
end
The example will print `.TRUE.' unless you are using a platform
where default `REAL' variables are unusually padded.
_See also_:
*Note SIZEOF::

File: gfortran.info, Node: CEILING, Next: CHAR, Prev: C_SIZEOF, Up: Intrinsic Procedures
8.38 `CEILING' -- Integer ceiling function
==========================================
_Description_:
`CEILING(A)' returns the least integer greater than or equal to A.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = CEILING(A [, KIND])'
_Arguments_:
A The type shall be `REAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER(KIND)' if KIND is present and
a default-kind `INTEGER' otherwise.
_Example_:
program test_ceiling
real :: x = 63.29
real :: y = -63.59
print *, ceiling(x) ! returns 64
print *, ceiling(y) ! returns -63
end program test_ceiling
_See also_:
*Note FLOOR::, *Note NINT::

File: gfortran.info, Node: CHAR, Next: CHDIR, Prev: CEILING, Up: Intrinsic Procedures
8.39 `CHAR' -- Character conversion function
============================================
_Description_:
`CHAR(I [, KIND])' returns the character represented by the
integer I.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = CHAR(I [, KIND])'
_Arguments_:
I The type shall be `INTEGER'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `CHARACTER(1)'
_Example_:
program test_char
integer :: i = 74
character(1) :: c
c = char(i)
print *, i, c ! returns 'J'
end program test_char
_Note_:
See *Note ICHAR:: for a discussion of converting between numerical
values and formatted string representations.
_See also_:
*Note ACHAR::, *Note IACHAR::, *Note ICHAR::

File: gfortran.info, Node: CHDIR, Next: CHMOD, Prev: CHAR, Up: Intrinsic Procedures
8.40 `CHDIR' -- Change working directory
========================================
_Description_:
Change current working directory to a specified path.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL CHDIR(NAME [, STATUS])'
`STATUS = CHDIR(NAME)'
_Arguments_:
NAME The type shall be `CHARACTER' of default kind
and shall specify a valid path within the file
system.
STATUS (Optional) `INTEGER' status flag of the default
kind. Returns 0 on success, and a system
specific and nonzero error code otherwise.
_Example_:
PROGRAM test_chdir
CHARACTER(len=255) :: path
CALL getcwd(path)
WRITE(*,*) TRIM(path)
CALL chdir("/tmp")
CALL getcwd(path)
WRITE(*,*) TRIM(path)
END PROGRAM
_See also_:
*Note GETCWD::

File: gfortran.info, Node: CHMOD, Next: CMPLX, Prev: CHDIR, Up: Intrinsic Procedures
8.41 `CHMOD' -- Change access permissions of files
==================================================
_Description_:
`CHMOD' changes the permissions of a file. This function invokes
`/bin/chmod' and might therefore not work on all platforms.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL CHMOD(NAME, MODE[, STATUS])'
`STATUS = CHMOD(NAME, MODE)'
_Arguments_:
NAME Scalar `CHARACTER' of default kind with the
file name. Trailing blanks are ignored unless
the character `achar(0)' is present, then all
characters up to and excluding `achar(0)' are
used as the file name.
MODE Scalar `CHARACTER' of default kind giving the
file permission. MODE uses the same syntax as
the MODE argument of `/bin/chmod'.
STATUS (optional) scalar `INTEGER', which is `0' on
success and nonzero otherwise.
_Return value_:
In either syntax, STATUS is set to `0' on success and nonzero
otherwise.
_Example_:
`CHMOD' as subroutine
program chmod_test
implicit none
integer :: status
call chmod('test.dat','u+x',status)
print *, 'Status: ', status
end program chmod_test
`CHMOD' as function:
program chmod_test
implicit none
integer :: status
status = chmod('test.dat','u+x')
print *, 'Status: ', status
end program chmod_test

File: gfortran.info, Node: CMPLX, Next: COMMAND_ARGUMENT_COUNT, Prev: CHMOD, Up: Intrinsic Procedures
8.42 `CMPLX' -- Complex conversion function
===========================================
_Description_:
`CMPLX(X [, Y [, KIND]])' returns a complex number where X is
converted to the real component. If Y is present it is converted
to the imaginary component. If Y is not present then the
imaginary component is set to 0.0. If X is complex then Y must
not be present.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = CMPLX(X [, Y [, KIND]])'
_Arguments_:
X The type may be `INTEGER', `REAL', or
`COMPLEX'.
Y (Optional; only allowed if X is not
`COMPLEX'.) May be `INTEGER' or `REAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of `COMPLEX' type, with a kind equal to KIND
if it is specified. If KIND is not specified, the result is of
the default `COMPLEX' kind, regardless of the kinds of X and Y.
_Example_:
program test_cmplx
integer :: i = 42
real :: x = 3.14
complex :: z
z = cmplx(i, x)
print *, z, cmplx(x)
end program test_cmplx
_See also_:
*Note COMPLEX::

File: gfortran.info, Node: COMMAND_ARGUMENT_COUNT, Next: COMPLEX, Prev: CMPLX, Up: Intrinsic Procedures
8.43 `COMMAND_ARGUMENT_COUNT' -- Get number of command line arguments
=====================================================================
_Description_:
`COMMAND_ARGUMENT_COUNT()' returns the number of arguments passed
on the command line when the containing program was invoked.
_Standard_:
Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = COMMAND_ARGUMENT_COUNT()'
_Arguments_:
None
_Return value_:
The return value is an `INTEGER' of default kind.
_Example_:
program test_command_argument_count
integer :: count
count = command_argument_count()
print *, count
end program test_command_argument_count
_See also_:
*Note GET_COMMAND::, *Note GET_COMMAND_ARGUMENT::

File: gfortran.info, Node: COMPLEX, Next: CONJG, Prev: COMMAND_ARGUMENT_COUNT, Up: Intrinsic Procedures
8.44 `COMPLEX' -- Complex conversion function
=============================================
_Description_:
`COMPLEX(X, Y)' returns a complex number where X is converted to
the real component and Y is converted to the imaginary component.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = COMPLEX(X, Y)'
_Arguments_:
X The type may be `INTEGER' or `REAL'.
Y The type may be `INTEGER' or `REAL'.
_Return value_:
If X and Y are both of `INTEGER' type, then the return value is of
default `COMPLEX' type.
If X and Y are of `REAL' type, or one is of `REAL' type and one is
of `INTEGER' type, then the return value is of `COMPLEX' type with
a kind equal to that of the `REAL' argument with the highest
precision.
_Example_:
program test_complex
integer :: i = 42
real :: x = 3.14
print *, complex(i, x)
end program test_complex
_See also_:
*Note CMPLX::

File: gfortran.info, Node: CONJG, Next: COS, Prev: COMPLEX, Up: Intrinsic Procedures
8.45 `CONJG' -- Complex conjugate function
==========================================
_Description_:
`CONJG(Z)' returns the conjugate of Z. If Z is `(x, y)' then the
result is `(x, -y)'
_Standard_:
Fortran 77 and later, has overloads that are GNU extensions
_Class_:
Elemental function
_Syntax_:
`Z = CONJG(Z)'
_Arguments_:
Z The type shall be `COMPLEX'.
_Return value_:
The return value is of type `COMPLEX'.
_Example_:
program test_conjg
complex :: z = (2.0, 3.0)
complex(8) :: dz = (2.71_8, -3.14_8)
z= conjg(z)
print *, z
dz = dconjg(dz)
print *, dz
end program test_conjg
_Specific names_:
Name Argument Return type Standard
`DCONJG(Z)' `COMPLEX(8) `COMPLEX(8)' GNU extension
Z'

File: gfortran.info, Node: COS, Next: COSH, Prev: CONJG, Up: Intrinsic Procedures
8.46 `COS' -- Cosine function
=============================
_Description_:
`COS(X)' computes the cosine of X.
_Standard_:
Fortran 77 and later, has overloads that are GNU extensions
_Class_:
Elemental function
_Syntax_:
`RESULT = COS(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value is of the same type and kind as X. The real part
of the result is in radians. If X is of the type `REAL', the
return value lies in the range -1 \leq \cos (x) \leq 1.
_Example_:
program test_cos
real :: x = 0.0
x = cos(x)
end program test_cos
_Specific names_:
Name Argument Return type Standard
`DCOS(X)' `REAL(8) X' `REAL(8)' Fortran 77 and
later
`CCOS(X)' `COMPLEX(4) `COMPLEX(4)' Fortran 77 and
X' later
`ZCOS(X)' `COMPLEX(8) `COMPLEX(8)' GNU extension
X'
`CDCOS(X)' `COMPLEX(8) `COMPLEX(8)' GNU extension
X'
_See also_:
Inverse function: *Note ACOS::

File: gfortran.info, Node: COSH, Next: COUNT, Prev: COS, Up: Intrinsic Procedures
8.47 `COSH' -- Hyperbolic cosine function
=========================================
_Description_:
`COSH(X)' computes the hyperbolic cosine of X.
_Standard_:
Fortran 77 and later, for a complex argument Fortran 2008 or later
_Class_:
Elemental function
_Syntax_:
`X = COSH(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has same type and kind as X. If X is complex, the
imaginary part of the result is in radians. If X is `REAL', the
return value has a lower bound of one, \cosh (x) \geq 1.
_Example_:
program test_cosh
real(8) :: x = 1.0_8
x = cosh(x)
end program test_cosh
_Specific names_:
Name Argument Return type Standard
`DCOSH(X)' `REAL(8) X' `REAL(8)' Fortran 77 and
later
_See also_:
Inverse function: *Note ACOSH::

File: gfortran.info, Node: COUNT, Next: CPU_TIME, Prev: COSH, Up: Intrinsic Procedures
8.48 `COUNT' -- Count function
==============================
_Description_:
Counts the number of `.TRUE.' elements in a logical MASK, or, if
the DIM argument is supplied, counts the number of elements along
each row of the array in the DIM direction. If the array has zero
size, or all of the elements of MASK are `.FALSE.', then the
result is `0'.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = COUNT(MASK [, DIM, KIND])'
_Arguments_:
MASK The type shall be `LOGICAL'.
DIM (Optional) The type shall be `INTEGER'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind. If DIM is
present, the result is an array with a rank one less than the rank
of ARRAY, and a size corresponding to the shape of ARRAY with the
DIM dimension removed.
_Example_:
program test_count
integer, dimension(2,3) :: a, b
logical, dimension(2,3) :: mask
a = reshape( (/ 1, 2, 3, 4, 5, 6 /), (/ 2, 3 /))
b = reshape( (/ 0, 7, 3, 4, 5, 8 /), (/ 2, 3 /))
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print *
print '(3i3)', b(1,:)
print '(3i3)', b(2,:)
print *
mask = a.ne.b
print '(3l3)', mask(1,:)
print '(3l3)', mask(2,:)
print *
print '(3i3)', count(mask)
print *
print '(3i3)', count(mask, 1)
print *
print '(3i3)', count(mask, 2)
end program test_count

File: gfortran.info, Node: CPU_TIME, Next: CSHIFT, Prev: COUNT, Up: Intrinsic Procedures
8.49 `CPU_TIME' -- CPU elapsed time in seconds
==============================================
_Description_:
Returns a `REAL' value representing the elapsed CPU time in
seconds. This is useful for testing segments of code to determine
execution time.
If a time source is available, time will be reported with
microsecond resolution. If no time source is available, TIME is
set to `-1.0'.
Note that TIME may contain a, system dependent, arbitrary offset
and may not start with `0.0'. For `CPU_TIME', the absolute value
is meaningless, only differences between subsequent calls to this
subroutine, as shown in the example below, should be used.
_Standard_:
Fortran 95 and later
_Class_:
Subroutine
_Syntax_:
`CALL CPU_TIME(TIME)'
_Arguments_:
TIME The type shall be `REAL' with `INTENT(OUT)'.
_Return value_:
None
_Example_:
program test_cpu_time
real :: start, finish
call cpu_time(start)
! put code to test here
call cpu_time(finish)
print '("Time = ",f6.3," seconds.")',finish-start
end program test_cpu_time
_See also_:
*Note SYSTEM_CLOCK::, *Note DATE_AND_TIME::

File: gfortran.info, Node: CSHIFT, Next: CTIME, Prev: CPU_TIME, Up: Intrinsic Procedures
8.50 `CSHIFT' -- Circular shift elements of an array
====================================================
_Description_:
`CSHIFT(ARRAY, SHIFT [, DIM])' performs a circular shift on
elements of ARRAY along the dimension of DIM. If DIM is omitted
it is taken to be `1'. DIM is a scalar of type `INTEGER' in the
range of 1 \leq DIM \leq n) where n is the rank of ARRAY. If the
rank of ARRAY is one, then all elements of ARRAY are shifted by
SHIFT places. If rank is greater than one, then all complete rank
one sections of ARRAY along the given dimension are shifted.
Elements shifted out one end of each rank one section are shifted
back in the other end.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = CSHIFT(ARRAY, SHIFT [, DIM])'
_Arguments_:
ARRAY Shall be an array of any type.
SHIFT The type shall be `INTEGER'.
DIM The type shall be `INTEGER'.
_Return value_:
Returns an array of same type and rank as the ARRAY argument.
_Example_:
program test_cshift
integer, dimension(3,3) :: a
a = reshape( (/ 1, 2, 3, 4, 5, 6, 7, 8, 9 /), (/ 3, 3 /))
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
a = cshift(a, SHIFT=(/1, 2, -1/), DIM=2)
print *
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
end program test_cshift

File: gfortran.info, Node: CTIME, Next: DATE_AND_TIME, Prev: CSHIFT, Up: Intrinsic Procedures
8.51 `CTIME' -- Convert a time into a string
============================================
_Description_:
`CTIME' converts a system time value, such as returned by
`TIME8()', to a string of the form `Sat Aug 19 18:13:14 1995'.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL CTIME(TIME, RESULT)'.
`RESULT = CTIME(TIME)', (not recommended).
_Arguments_:
TIME The type shall be of type `INTEGER(KIND=8)'.
RESULT The type shall be of type `CHARACTER' and of
default kind.
_Return value_:
The converted date and time as a string.
_Example_:
program test_ctime
integer(8) :: i
character(len=30) :: date
i = time8()
! Do something, main part of the program
call ctime(i,date)
print *, 'Program was started on ', date
end program test_ctime
_See Also_:
*Note GMTIME::, *Note LTIME::, *Note TIME::, *Note TIME8::

File: gfortran.info, Node: DATE_AND_TIME, Next: DBLE, Prev: CTIME, Up: Intrinsic Procedures
8.52 `DATE_AND_TIME' -- Date and time subroutine
================================================
_Description_:
`DATE_AND_TIME(DATE, TIME, ZONE, VALUES)' gets the corresponding
date and time information from the real-time system clock. DATE is
`INTENT(OUT)' and has form ccyymmdd. TIME is `INTENT(OUT)' and
has form hhmmss.sss. ZONE is `INTENT(OUT)' and has form (+-)hhmm,
representing the difference with respect to Coordinated Universal
Time (UTC). Unavailable time and date parameters return blanks.
VALUES is `INTENT(OUT)' and provides the following:
`VALUE(1)': The year
`VALUE(2)': The month
`VALUE(3)': The day of the month
`VALUE(4)': Time difference with UTC
in minutes
`VALUE(5)': The hour of the day
`VALUE(6)': The minutes of the hour
`VALUE(7)': The seconds of the minute
`VALUE(8)': The milliseconds of the
second
_Standard_:
Fortran 95 and later
_Class_:
Subroutine
_Syntax_:
`CALL DATE_AND_TIME([DATE, TIME, ZONE, VALUES])'
_Arguments_:
DATE (Optional) The type shall be `CHARACTER(LEN=8)'
or larger, and of default kind.
TIME (Optional) The type shall be
`CHARACTER(LEN=10)' or larger, and of default
kind.
ZONE (Optional) The type shall be `CHARACTER(LEN=5)'
or larger, and of default kind.
VALUES (Optional) The type shall be `INTEGER(8)'.
_Return value_:
None
_Example_:
program test_time_and_date
character(8) :: date
character(10) :: time
character(5) :: zone
integer,dimension(8) :: values
! using keyword arguments
call date_and_time(date,time,zone,values)
call date_and_time(DATE=date,ZONE=zone)
call date_and_time(TIME=time)
call date_and_time(VALUES=values)
print '(a,2x,a,2x,a)', date, time, zone
print '(8i5))', values
end program test_time_and_date
_See also_:
*Note CPU_TIME::, *Note SYSTEM_CLOCK::

File: gfortran.info, Node: DBLE, Next: DCMPLX, Prev: DATE_AND_TIME, Up: Intrinsic Procedures
8.53 `DBLE' -- Double conversion function
=========================================
_Description_:
`DBLE(A)' Converts A to double precision real type.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = DBLE(A)'
_Arguments_:
A The type shall be `INTEGER', `REAL', or
`COMPLEX'.
_Return value_:
The return value is of type double precision real.
_Example_:
program test_dble
real :: x = 2.18
integer :: i = 5
complex :: z = (2.3,1.14)
print *, dble(x), dble(i), dble(z)
end program test_dble
_See also_:
*Note DFLOAT::, *Note FLOAT::, *Note REAL::

File: gfortran.info, Node: DCMPLX, Next: DFLOAT, Prev: DBLE, Up: Intrinsic Procedures
8.54 `DCMPLX' -- Double complex conversion function
===================================================
_Description_:
`DCMPLX(X [,Y])' returns a double complex number where X is
converted to the real component. If Y is present it is converted
to the imaginary component. If Y is not present then the
imaginary component is set to 0.0. If X is complex then Y must
not be present.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = DCMPLX(X [, Y])'
_Arguments_:
X The type may be `INTEGER', `REAL', or
`COMPLEX'.
Y (Optional if X is not `COMPLEX'.) May be
`INTEGER' or `REAL'.
_Return value_:
The return value is of type `COMPLEX(8)'
_Example_:
program test_dcmplx
integer :: i = 42
real :: x = 3.14
complex :: z
z = cmplx(i, x)
print *, dcmplx(i)
print *, dcmplx(x)
print *, dcmplx(z)
print *, dcmplx(x,i)
end program test_dcmplx

File: gfortran.info, Node: DFLOAT, Next: DIGITS, Prev: DCMPLX, Up: Intrinsic Procedures
8.55 `DFLOAT' -- Double conversion function
===========================================
_Description_:
`DFLOAT(A)' Converts A to double precision real type.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = DFLOAT(A)'
_Arguments_:
A The type shall be `INTEGER'.
_Return value_:
The return value is of type double precision real.
_Example_:
program test_dfloat
integer :: i = 5
print *, dfloat(i)
end program test_dfloat
_See also_:
*Note DBLE::, *Note FLOAT::, *Note REAL::

File: gfortran.info, Node: DIGITS, Next: DIM, Prev: DFLOAT, Up: Intrinsic Procedures
8.56 `DIGITS' -- Significant binary digits function
===================================================
_Description_:
`DIGITS(X)' returns the number of significant binary digits of the
internal model representation of X. For example, on a system
using a 32-bit floating point representation, a default real
number would likely return 24.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = DIGITS(X)'
_Arguments_:
X The type may be `INTEGER' or `REAL'.
_Return value_:
The return value is of type `INTEGER'.
_Example_:
program test_digits
integer :: i = 12345
real :: x = 3.143
real(8) :: y = 2.33
print *, digits(i)
print *, digits(x)
print *, digits(y)
end program test_digits

File: gfortran.info, Node: DIM, Next: DOT_PRODUCT, Prev: DIGITS, Up: Intrinsic Procedures
8.57 `DIM' -- Positive difference
=================================
_Description_:
`DIM(X,Y)' returns the difference `X-Y' if the result is positive;
otherwise returns zero.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = DIM(X, Y)'
_Arguments_:
X The type shall be `INTEGER' or `REAL'
Y The type shall be the same type and kind as X.
_Return value_:
The return value is of type `INTEGER' or `REAL'.
_Example_:
program test_dim
integer :: i
real(8) :: x
i = dim(4, 15)
x = dim(4.345_8, 2.111_8)
print *, i
print *, x
end program test_dim
_Specific names_:
Name Argument Return type Standard
`IDIM(X,Y)' `INTEGER(4) `INTEGER(4)' Fortran 77 and
X,Y' later
`DDIM(X,Y)' `REAL(8) `REAL(8)' Fortran 77 and
X,Y' later

File: gfortran.info, Node: DOT_PRODUCT, Next: DPROD, Prev: DIM, Up: Intrinsic Procedures
8.58 `DOT_PRODUCT' -- Dot product function
==========================================
_Description_:
`DOT_PRODUCT(VECTOR_A, VECTOR_B)' computes the dot product
multiplication of two vectors VECTOR_A and VECTOR_B. The two
vectors may be either numeric or logical and must be arrays of
rank one and of equal size. If the vectors are `INTEGER' or
`REAL', the result is `SUM(VECTOR_A*VECTOR_B)'. If the vectors are
`COMPLEX', the result is `SUM(CONJG(VECTOR_A)*VECTOR_B)'. If the
vectors are `LOGICAL', the result is `ANY(VECTOR_A .AND.
VECTOR_B)'.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = DOT_PRODUCT(VECTOR_A, VECTOR_B)'
_Arguments_:
VECTOR_A The type shall be numeric or `LOGICAL', rank 1.
VECTOR_B The type shall be numeric if VECTOR_A is of
numeric type or `LOGICAL' if VECTOR_A is of
type `LOGICAL'. VECTOR_B shall be a rank-one
array.
_Return value_:
If the arguments are numeric, the return value is a scalar of
numeric type, `INTEGER', `REAL', or `COMPLEX'. If the arguments
are `LOGICAL', the return value is `.TRUE.' or `.FALSE.'.
_Example_:
program test_dot_prod
integer, dimension(3) :: a, b
a = (/ 1, 2, 3 /)
b = (/ 4, 5, 6 /)
print '(3i3)', a
print *
print '(3i3)', b
print *
print *, dot_product(a,b)
end program test_dot_prod

File: gfortran.info, Node: DPROD, Next: DREAL, Prev: DOT_PRODUCT, Up: Intrinsic Procedures
8.59 `DPROD' -- Double product function
=======================================
_Description_:
`DPROD(X,Y)' returns the product `X*Y'.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = DPROD(X, Y)'
_Arguments_:
X The type shall be `REAL'.
Y The type shall be `REAL'.
_Return value_:
The return value is of type `REAL(8)'.
_Example_:
program test_dprod
real :: x = 5.2
real :: y = 2.3
real(8) :: d
d = dprod(x,y)
print *, d
end program test_dprod

File: gfortran.info, Node: DREAL, Next: DTIME, Prev: DPROD, Up: Intrinsic Procedures
8.60 `DREAL' -- Double real part function
=========================================
_Description_:
`DREAL(Z)' returns the real part of complex variable Z.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = DREAL(A)'
_Arguments_:
A The type shall be `COMPLEX(8)'.
_Return value_:
The return value is of type `REAL(8)'.
_Example_:
program test_dreal
complex(8) :: z = (1.3_8,7.2_8)
print *, dreal(z)
end program test_dreal
_See also_:
*Note AIMAG::

File: gfortran.info, Node: DTIME, Next: EOSHIFT, Prev: DREAL, Up: Intrinsic Procedures
8.61 `DTIME' -- Execution time subroutine (or function)
=======================================================
_Description_:
`DTIME(VALUES, TIME)' initially returns the number of seconds of
runtime since the start of the process's execution in TIME. VALUES
returns the user and system components of this time in `VALUES(1)'
and `VALUES(2)' respectively. TIME is equal to `VALUES(1) +
VALUES(2)'.
Subsequent invocations of `DTIME' return values accumulated since
the previous invocation.
On some systems, the underlying timings are represented using
types with sufficiently small limits that overflows (wrap around)
are possible, such as 32-bit types. Therefore, the values returned
by this intrinsic might be, or become, negative, or numerically
less than previous values, during a single run of the compiled
program.
Please note, that this implementation is thread safe if used
within OpenMP directives, i.e., its state will be consistent while
called from multiple threads. However, if `DTIME' is called from
multiple threads, the result is still the time since the last
invocation. This may not give the intended results. If possible,
use `CPU_TIME' instead.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
VALUES and TIME are `INTENT(OUT)' and provide the following:
`VALUES(1)': User time in seconds.
`VALUES(2)': System time in seconds.
`TIME': Run time since start in
seconds.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL DTIME(VALUES, TIME)'.
`TIME = DTIME(VALUES)', (not recommended).
_Arguments_:
VALUES The type shall be `REAL(4), DIMENSION(2)'.
TIME The type shall be `REAL(4)'.
_Return value_:
Elapsed time in seconds since the last invocation or since the
start of program execution if not called before.
_Example_:
program test_dtime
integer(8) :: i, j
real, dimension(2) :: tarray
real :: result
call dtime(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
do i=1,100000000 ! Just a delay
j = i * i - i
end do
call dtime(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
end program test_dtime
_See also_:
*Note CPU_TIME::

File: gfortran.info, Node: EOSHIFT, Next: EPSILON, Prev: DTIME, Up: Intrinsic Procedures
8.62 `EOSHIFT' -- End-off shift elements of an array
====================================================
_Description_:
`EOSHIFT(ARRAY, SHIFT[, BOUNDARY, DIM])' performs an end-off shift
on elements of ARRAY along the dimension of DIM. If DIM is
omitted it is taken to be `1'. DIM is a scalar of type `INTEGER'
in the range of 1 \leq DIM \leq n) where n is the rank of ARRAY.
If the rank of ARRAY is one, then all elements of ARRAY are
shifted by SHIFT places. If rank is greater than one, then all
complete rank one sections of ARRAY along the given dimension are
shifted. Elements shifted out one end of each rank one section
are dropped. If BOUNDARY is present then the corresponding value
of from BOUNDARY is copied back in the other end. If BOUNDARY is
not present then the following are copied in depending on the type
of ARRAY.
_Array _Boundary Value_
Type_
Numeric 0 of the type and kind of ARRAY.
Logical `.FALSE.'.
Character(LEN)LEN blanks.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = EOSHIFT(ARRAY, SHIFT [, BOUNDARY, DIM])'
_Arguments_:
ARRAY May be any type, not scalar.
SHIFT The type shall be `INTEGER'.
BOUNDARY Same type as ARRAY.
DIM The type shall be `INTEGER'.
_Return value_:
Returns an array of same type and rank as the ARRAY argument.
_Example_:
program test_eoshift
integer, dimension(3,3) :: a
a = reshape( (/ 1, 2, 3, 4, 5, 6, 7, 8, 9 /), (/ 3, 3 /))
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
a = EOSHIFT(a, SHIFT=(/1, 2, 1/), BOUNDARY=-5, DIM=2)
print *
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
end program test_eoshift

File: gfortran.info, Node: EPSILON, Next: ERF, Prev: EOSHIFT, Up: Intrinsic Procedures
8.63 `EPSILON' -- Epsilon function
==================================
_Description_:
`EPSILON(X)' returns the smallest number E of the same kind as X
such that 1 + E > 1.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = EPSILON(X)'
_Arguments_:
X The type shall be `REAL'.
_Return value_:
The return value is of same type as the argument.
_Example_:
program test_epsilon
real :: x = 3.143
real(8) :: y = 2.33
print *, EPSILON(x)
print *, EPSILON(y)
end program test_epsilon

File: gfortran.info, Node: ERF, Next: ERFC, Prev: EPSILON, Up: Intrinsic Procedures
8.64 `ERF' -- Error function
============================
_Description_:
`ERF(X)' computes the error function of X.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ERF(X)'
_Arguments_:
X The type shall be `REAL'.
_Return value_:
The return value is of type `REAL', of the same kind as X and lies
in the range -1 \leq erf (x) \leq 1 .
_Example_:
program test_erf
real(8) :: x = 0.17_8
x = erf(x)
end program test_erf
_Specific names_:
Name Argument Return type Standard
`DERF(X)' `REAL(8) X' `REAL(8)' GNU extension

File: gfortran.info, Node: ERFC, Next: ERFC_SCALED, Prev: ERF, Up: Intrinsic Procedures
8.65 `ERFC' -- Error function
=============================
_Description_:
`ERFC(X)' computes the complementary error function of X.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ERFC(X)'
_Arguments_:
X The type shall be `REAL'.
_Return value_:
The return value is of type `REAL' and of the same kind as X. It
lies in the range 0 \leq erfc (x) \leq 2 .
_Example_:
program test_erfc
real(8) :: x = 0.17_8
x = erfc(x)
end program test_erfc
_Specific names_:
Name Argument Return type Standard
`DERFC(X)' `REAL(8) X' `REAL(8)' GNU extension

File: gfortran.info, Node: ERFC_SCALED, Next: ETIME, Prev: ERFC, Up: Intrinsic Procedures
8.66 `ERFC_SCALED' -- Error function
====================================
_Description_:
`ERFC_SCALED(X)' computes the exponentially-scaled complementary
error function of X.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ERFC_SCALED(X)'
_Arguments_:
X The type shall be `REAL'.
_Return value_:
The return value is of type `REAL' and of the same kind as X.
_Example_:
program test_erfc_scaled
real(8) :: x = 0.17_8
x = erfc_scaled(x)
end program test_erfc_scaled

File: gfortran.info, Node: ETIME, Next: EXIT, Prev: ERFC_SCALED, Up: Intrinsic Procedures
8.67 `ETIME' -- Execution time subroutine (or function)
=======================================================
_Description_:
`ETIME(VALUES, TIME)' returns the number of seconds of runtime
since the start of the process's execution in TIME. VALUES
returns the user and system components of this time in `VALUES(1)'
and `VALUES(2)' respectively. TIME is equal to `VALUES(1) +
VALUES(2)'.
On some systems, the underlying timings are represented using
types with sufficiently small limits that overflows (wrap around)
are possible, such as 32-bit types. Therefore, the values returned
by this intrinsic might be, or become, negative, or numerically
less than previous values, during a single run of the compiled
program.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
VALUES and TIME are `INTENT(OUT)' and provide the following:
`VALUES(1)': User time in seconds.
`VALUES(2)': System time in seconds.
`TIME': Run time since start in seconds.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL ETIME(VALUES, TIME)'.
`TIME = ETIME(VALUES)', (not recommended).
_Arguments_:
VALUES The type shall be `REAL(4), DIMENSION(2)'.
TIME The type shall be `REAL(4)'.
_Return value_:
Elapsed time in seconds since the start of program execution.
_Example_:
program test_etime
integer(8) :: i, j
real, dimension(2) :: tarray
real :: result
call ETIME(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
do i=1,100000000 ! Just a delay
j = i * i - i
end do
call ETIME(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
end program test_etime
_See also_:
*Note CPU_TIME::

File: gfortran.info, Node: EXIT, Next: EXP, Prev: ETIME, Up: Intrinsic Procedures
8.68 `EXIT' -- Exit the program with status.
============================================
_Description_:
`EXIT' causes immediate termination of the program with status.
If status is omitted it returns the canonical _success_ for the
system. All Fortran I/O units are closed.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL EXIT([STATUS])'
_Arguments_:
STATUS Shall be an `INTEGER' of the default kind.
_Return value_:
`STATUS' is passed to the parent process on exit.
_Example_:
program test_exit
integer :: STATUS = 0
print *, 'This program is going to exit.'
call EXIT(STATUS)
end program test_exit
_See also_:
*Note ABORT::, *Note KILL::

File: gfortran.info, Node: EXP, Next: EXPONENT, Prev: EXIT, Up: Intrinsic Procedures
8.69 `EXP' -- Exponential function
==================================
_Description_:
`EXP(X)' computes the base e exponential of X.
_Standard_:
Fortran 77 and later, has overloads that are GNU extensions
_Class_:
Elemental function
_Syntax_:
`RESULT = EXP(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has same type and kind as X.
_Example_:
program test_exp
real :: x = 1.0
x = exp(x)
end program test_exp
_Specific names_:
Name Argument Return type Standard
`DEXP(X)' `REAL(8) X' `REAL(8)' Fortran 77 and
later
`CEXP(X)' `COMPLEX(4) `COMPLEX(4)' Fortran 77 and
X' later
`ZEXP(X)' `COMPLEX(8) `COMPLEX(8)' GNU extension
X'
`CDEXP(X)' `COMPLEX(8) `COMPLEX(8)' GNU extension
X'

File: gfortran.info, Node: EXPONENT, Next: FDATE, Prev: EXP, Up: Intrinsic Procedures
8.70 `EXPONENT' -- Exponent function
====================================
_Description_:
`EXPONENT(X)' returns the value of the exponent part of X. If X is
zero the value returned is zero.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = EXPONENT(X)'
_Arguments_:
X The type shall be `REAL'.
_Return value_:
The return value is of type default `INTEGER'.
_Example_:
program test_exponent
real :: x = 1.0
integer :: i
i = exponent(x)
print *, i
print *, exponent(0.0)
end program test_exponent

File: gfortran.info, Node: FDATE, Next: FGET, Prev: EXPONENT, Up: Intrinsic Procedures
8.71 `FDATE' -- Get the current time as a string
================================================
_Description_:
`FDATE(DATE)' returns the current date (using the same format as
`CTIME') in DATE. It is equivalent to `CALL CTIME(DATE, TIME())'.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
DATE is an `INTENT(OUT)' `CHARACTER' variable of the default kind.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL FDATE(DATE)'.
`DATE = FDATE()', (not recommended).
_Arguments_:
DATE The type shall be of type `CHARACTER' of the
default kind
_Return value_:
The current date as a string.
_Example_:
program test_fdate
integer(8) :: i, j
character(len=30) :: date
call fdate(date)
print *, 'Program started on ', date
do i = 1, 100000000 ! Just a delay
j = i * i - i
end do
call fdate(date)
print *, 'Program ended on ', date
end program test_fdate

File: gfortran.info, Node: FLOAT, Next: FLOOR, Prev: FGETC, Up: Intrinsic Procedures
8.72 `FLOAT' -- Convert integer to default real
===============================================
_Description_:
`FLOAT(A)' converts the integer A to a default real value.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = FLOAT(A)'
_Arguments_:
A The type shall be `INTEGER'.
_Return value_:
The return value is of type default `REAL'.
_Example_:
program test_float
integer :: i = 1
if (float(i) /= 1.) call abort
end program test_float
_See also_:
*Note DBLE::, *Note DFLOAT::, *Note REAL::

File: gfortran.info, Node: FGET, Next: FGETC, Prev: FDATE, Up: Intrinsic Procedures
8.73 `FGET' -- Read a single character in stream mode from stdin
================================================================
_Description_:
Read a single character in stream mode from stdin by bypassing
normal formatted output. Stream I/O should not be mixed with
normal record-oriented (formatted or unformatted) I/O on the same
unit; the results are unpredictable.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
Note that the `FGET' intrinsic is provided for backwards
compatibility with `g77'. GNU Fortran provides the Fortran 2003
Stream facility. Programmers should consider the use of new
stream IO feature in new code for future portability. See also
*Note Fortran 2003 status::.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL FGET(C [, STATUS])'
_Arguments_:
C The type shall be `CHARACTER' and of default
kind.
STATUS (Optional) status flag of type `INTEGER'.
Returns 0 on success, -1 on end-of-file, and a
system specific positive error code otherwise.
_Example_:
PROGRAM test_fget
INTEGER, PARAMETER :: strlen = 100
INTEGER :: status, i = 1
CHARACTER(len=strlen) :: str = ""
WRITE (*,*) 'Enter text:'
DO
CALL fget(str(i:i), status)
if (status /= 0 .OR. i > strlen) exit
i = i + 1
END DO
WRITE (*,*) TRIM(str)
END PROGRAM
_See also_:
*Note FGETC::, *Note FPUT::, *Note FPUTC::

File: gfortran.info, Node: FGETC, Next: FLOAT, Prev: FGET, Up: Intrinsic Procedures
8.74 `FGETC' -- Read a single character in stream mode
======================================================
_Description_:
Read a single character in stream mode by bypassing normal
formatted output. Stream I/O should not be mixed with normal
record-oriented (formatted or unformatted) I/O on the same unit;
the results are unpredictable.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
Note that the `FGET' intrinsic is provided for backwards
compatibility with `g77'. GNU Fortran provides the Fortran 2003
Stream facility. Programmers should consider the use of new
stream IO feature in new code for future portability. See also
*Note Fortran 2003 status::.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL FGETC(UNIT, C [, STATUS])'
_Arguments_:
UNIT The type shall be `INTEGER'.
C The type shall be `CHARACTER' and of default
kind.
STATUS (Optional) status flag of type `INTEGER'.
Returns 0 on success, -1 on end-of-file and a
system specific positive error code otherwise.
_Example_:
PROGRAM test_fgetc
INTEGER :: fd = 42, status
CHARACTER :: c
OPEN(UNIT=fd, FILE="/etc/passwd", ACTION="READ", STATUS = "OLD")
DO
CALL fgetc(fd, c, status)
IF (status /= 0) EXIT
call fput(c)
END DO
CLOSE(UNIT=fd)
END PROGRAM
_See also_:
*Note FGET::, *Note FPUT::, *Note FPUTC::

File: gfortran.info, Node: FLOOR, Next: FLUSH, Prev: FLOAT, Up: Intrinsic Procedures
8.75 `FLOOR' -- Integer floor function
======================================
_Description_:
`FLOOR(A)' returns the greatest integer less than or equal to X.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = FLOOR(A [, KIND])'
_Arguments_:
A The type shall be `REAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER(KIND)' if KIND is present and
of default-kind `INTEGER' otherwise.
_Example_:
program test_floor
real :: x = 63.29
real :: y = -63.59
print *, floor(x) ! returns 63
print *, floor(y) ! returns -64
end program test_floor
_See also_:
*Note CEILING::, *Note NINT::

File: gfortran.info, Node: FLUSH, Next: FNUM, Prev: FLOOR, Up: Intrinsic Procedures
8.76 `FLUSH' -- Flush I/O unit(s)
=================================
_Description_:
Flushes Fortran unit(s) currently open for output. Without the
optional argument, all units are flushed, otherwise just the unit
specified.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL FLUSH(UNIT)'
_Arguments_:
UNIT (Optional) The type shall be `INTEGER'.
_Note_:
Beginning with the Fortran 2003 standard, there is a `FLUSH'
statement that should be preferred over the `FLUSH' intrinsic.

File: gfortran.info, Node: FNUM, Next: FPUT, Prev: FLUSH, Up: Intrinsic Procedures
8.77 `FNUM' -- File number function
===================================
_Description_:
`FNUM(UNIT)' returns the POSIX file descriptor number
corresponding to the open Fortran I/O unit `UNIT'.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = FNUM(UNIT)'
_Arguments_:
UNIT The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER'
_Example_:
program test_fnum
integer :: i
open (unit=10, status = "scratch")
i = fnum(10)
print *, i
close (10)
end program test_fnum

File: gfortran.info, Node: FPUT, Next: FPUTC, Prev: FNUM, Up: Intrinsic Procedures
8.78 `FPUT' -- Write a single character in stream mode to stdout
================================================================
_Description_:
Write a single character in stream mode to stdout by bypassing
normal formatted output. Stream I/O should not be mixed with
normal record-oriented (formatted or unformatted) I/O on the same
unit; the results are unpredictable.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
Note that the `FGET' intrinsic is provided for backwards
compatibility with `g77'. GNU Fortran provides the Fortran 2003
Stream facility. Programmers should consider the use of new
stream IO feature in new code for future portability. See also
*Note Fortran 2003 status::.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL FPUT(C [, STATUS])'
_Arguments_:
C The type shall be `CHARACTER' and of default
kind.
STATUS (Optional) status flag of type `INTEGER'.
Returns 0 on success, -1 on end-of-file and a
system specific positive error code otherwise.
_Example_:
PROGRAM test_fput
CHARACTER(len=10) :: str = "gfortran"
INTEGER :: i
DO i = 1, len_trim(str)
CALL fput(str(i:i))
END DO
END PROGRAM
_See also_:
*Note FPUTC::, *Note FGET::, *Note FGETC::

File: gfortran.info, Node: FPUTC, Next: FRACTION, Prev: FPUT, Up: Intrinsic Procedures
8.79 `FPUTC' -- Write a single character in stream mode
=======================================================
_Description_:
Write a single character in stream mode by bypassing normal
formatted output. Stream I/O should not be mixed with normal
record-oriented (formatted or unformatted) I/O on the same unit;
the results are unpredictable.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
Note that the `FGET' intrinsic is provided for backwards
compatibility with `g77'. GNU Fortran provides the Fortran 2003
Stream facility. Programmers should consider the use of new
stream IO feature in new code for future portability. See also
*Note Fortran 2003 status::.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL FPUTC(UNIT, C [, STATUS])'
_Arguments_:
UNIT The type shall be `INTEGER'.
C The type shall be `CHARACTER' and of default
kind.
STATUS (Optional) status flag of type `INTEGER'.
Returns 0 on success, -1 on end-of-file and a
system specific positive error code otherwise.
_Example_:
PROGRAM test_fputc
CHARACTER(len=10) :: str = "gfortran"
INTEGER :: fd = 42, i
OPEN(UNIT = fd, FILE = "out", ACTION = "WRITE", STATUS="NEW")
DO i = 1, len_trim(str)
CALL fputc(fd, str(i:i))
END DO
CLOSE(fd)
END PROGRAM
_See also_:
*Note FPUT::, *Note FGET::, *Note FGETC::

File: gfortran.info, Node: FRACTION, Next: FREE, Prev: FPUTC, Up: Intrinsic Procedures
8.80 `FRACTION' -- Fractional part of the model representation
==============================================================
_Description_:
`FRACTION(X)' returns the fractional part of the model
representation of `X'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`Y = FRACTION(X)'
_Arguments_:
X The type of the argument shall be a `REAL'.
_Return value_:
The return value is of the same type and kind as the argument.
The fractional part of the model representation of `X' is returned;
it is `X * RADIX(X)**(-EXPONENT(X))'.
_Example_:
program test_fraction
real :: x
x = 178.1387e-4
print *, fraction(x), x * radix(x)**(-exponent(x))
end program test_fraction

File: gfortran.info, Node: FREE, Next: FSEEK, Prev: FRACTION, Up: Intrinsic Procedures
8.81 `FREE' -- Frees memory
===========================
_Description_:
Frees memory previously allocated by `MALLOC()'. The `FREE'
intrinsic is an extension intended to be used with Cray pointers,
and is provided in GNU Fortran to allow user to compile legacy
code. For new code using Fortran 95 pointers, the memory
de-allocation intrinsic is `DEALLOCATE'.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL FREE(PTR)'
_Arguments_:
PTR The type shall be `INTEGER'. It represents the
location of the memory that should be
de-allocated.
_Return value_:
None
_Example_:
See `MALLOC' for an example.
_See also_:
*Note MALLOC::

File: gfortran.info, Node: FSEEK, Next: FSTAT, Prev: FREE, Up: Intrinsic Procedures
8.82 `FSEEK' -- Low level file positioning subroutine
=====================================================
_Description_:
Moves UNIT to the specified OFFSET. If WHENCE is set to 0, the
OFFSET is taken as an absolute value `SEEK_SET', if set to 1,
OFFSET is taken to be relative to the current position `SEEK_CUR',
and if set to 2 relative to the end of the file `SEEK_END'. On
error, STATUS is set to a nonzero value. If STATUS the seek fails
silently.
This intrinsic routine is not fully backwards compatible with
`g77'. In `g77', the `FSEEK' takes a statement label instead of a
STATUS variable. If FSEEK is used in old code, change
CALL FSEEK(UNIT, OFFSET, WHENCE, *label)
to
INTEGER :: status
CALL FSEEK(UNIT, OFFSET, WHENCE, status)
IF (status /= 0) GOTO label
Please note that GNU Fortran provides the Fortran 2003 Stream
facility. Programmers should consider the use of new stream IO
feature in new code for future portability. See also *Note Fortran
2003 status::.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])'
_Arguments_:
UNIT Shall be a scalar of type `INTEGER'.
OFFSET Shall be a scalar of type `INTEGER'.
WHENCE Shall be a scalar of type `INTEGER'. Its
value shall be either 0, 1 or 2.
STATUS (Optional) shall be a scalar of type
`INTEGER(4)'.
_Example_:
PROGRAM test_fseek
INTEGER, PARAMETER :: SEEK_SET = 0, SEEK_CUR = 1, SEEK_END = 2
INTEGER :: fd, offset, ierr
ierr = 0
offset = 5
fd = 10
OPEN(UNIT=fd, FILE="fseek.test")
CALL FSEEK(fd, offset, SEEK_SET, ierr) ! move to OFFSET
print *, FTELL(fd), ierr
CALL FSEEK(fd, 0, SEEK_END, ierr) ! move to end
print *, FTELL(fd), ierr
CALL FSEEK(fd, 0, SEEK_SET, ierr) ! move to beginning
print *, FTELL(fd), ierr
CLOSE(UNIT=fd)
END PROGRAM
_See also_:
*Note FTELL::

File: gfortran.info, Node: FSTAT, Next: FTELL, Prev: FSEEK, Up: Intrinsic Procedures
8.83 `FSTAT' -- Get file status
===============================
_Description_:
`FSTAT' is identical to *Note STAT::, except that information
about an already opened file is obtained.
The elements in `VALUES' are the same as described by *Note STAT::.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL FSTAT(UNIT, VALUES [, STATUS])'
_Arguments_:
UNIT An open I/O unit number of type `INTEGER'.
VALUES The type shall be `INTEGER(4), DIMENSION(13)'.
STATUS (Optional) status flag of type `INTEGER(4)'.
Returns 0 on success and a system specific
error code otherwise.
_Example_:
See *Note STAT:: for an example.
_See also_:
To stat a link: *Note LSTAT::, to stat a file: *Note STAT::

File: gfortran.info, Node: FTELL, Next: GAMMA, Prev: FSTAT, Up: Intrinsic Procedures
8.84 `FTELL' -- Current stream position
=======================================
_Description_:
Retrieves the current position within an open file.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL FTELL(UNIT, OFFSET)'
`OFFSET = FTELL(UNIT)'
_Arguments_:
OFFSET Shall of type `INTEGER'.
UNIT Shall of type `INTEGER'.
_Return value_:
In either syntax, OFFSET is set to the current offset of unit
number UNIT, or to -1 if the unit is not currently open.
_Example_:
PROGRAM test_ftell
INTEGER :: i
OPEN(10, FILE="temp.dat")
CALL ftell(10,i)
WRITE(*,*) i
END PROGRAM
_See also_:
*Note FSEEK::

File: gfortran.info, Node: GAMMA, Next: GERROR, Prev: FTELL, Up: Intrinsic Procedures
8.85 `GAMMA' -- Gamma function
==============================
_Description_:
`GAMMA(X)' computes Gamma (\Gamma) of X. For positive, integer
values of X the Gamma function simplifies to the factorial
function \Gamma(x)=(x-1)!.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`X = GAMMA(X)'
_Arguments_:
X Shall be of type `REAL' and neither zero nor a
negative integer.
_Return value_:
The return value is of type `REAL' of the same kind as X.
_Example_:
program test_gamma
real :: x = 1.0
x = gamma(x) ! returns 1.0
end program test_gamma
_Specific names_:
Name Argument Return type Standard
`GAMMA(X)' `REAL(4) X' `REAL(4)' GNU Extension
`DGAMMA(X)' `REAL(8) X' `REAL(8)' GNU Extension
_See also_:
Logarithm of the Gamma function: *Note LOG_GAMMA::

File: gfortran.info, Node: GERROR, Next: GETARG, Prev: GAMMA, Up: Intrinsic Procedures
8.86 `GERROR' -- Get last system error message
==============================================
_Description_:
Returns the system error message corresponding to the last system
error. This resembles the functionality of `strerror(3)' in C.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL GERROR(RESULT)'
_Arguments_:
RESULT Shall of type `CHARACTER' and of default
_Example_:
PROGRAM test_gerror
CHARACTER(len=100) :: msg
CALL gerror(msg)
WRITE(*,*) msg
END PROGRAM
_See also_:
*Note IERRNO::, *Note PERROR::

File: gfortran.info, Node: GETARG, Next: GET_COMMAND, Prev: GERROR, Up: Intrinsic Procedures
8.87 `GETARG' -- Get command line arguments
===========================================
_Description_:
Retrieve the POS-th argument that was passed on the command line
when the containing program was invoked.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use
of the *Note GET_COMMAND_ARGUMENT:: intrinsic defined by the
Fortran 2003 standard.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL GETARG(POS, VALUE)'
_Arguments_:
POS Shall be of type `INTEGER' and not wider than
the default integer kind; POS \geq 0
VALUE Shall be of type `CHARACTER' and of default
kind.
VALUE Shall be of type `CHARACTER'.
_Return value_:
After `GETARG' returns, the VALUE argument holds the POSth command
line argument. If VALUE can not hold the argument, it is truncated
to fit the length of VALUE. If there are less than POS arguments
specified at the command line, VALUE will be filled with blanks.
If POS = 0, VALUE is set to the name of the program (on systems
that support this feature).
_Example_:
PROGRAM test_getarg
INTEGER :: i
CHARACTER(len=32) :: arg
DO i = 1, iargc()
CALL getarg(i, arg)
WRITE (*,*) arg
END DO
END PROGRAM
_See also_:
GNU Fortran 77 compatibility function: *Note IARGC::
Fortran 2003 functions and subroutines: *Note GET_COMMAND::, *Note
GET_COMMAND_ARGUMENT::, *Note COMMAND_ARGUMENT_COUNT::

File: gfortran.info, Node: GET_COMMAND, Next: GET_COMMAND_ARGUMENT, Prev: GETARG, Up: Intrinsic Procedures
8.88 `GET_COMMAND' -- Get the entire command line
=================================================
_Description_:
Retrieve the entire command line that was used to invoke the
program.
_Standard_:
Fortran 2003 and later
_Class_:
Subroutine
_Syntax_:
`CALL GET_COMMAND([COMMAND, LENGTH, STATUS])'
_Arguments_:
COMMAND (Optional) shall be of type `CHARACTER' and of
default kind.
LENGTH (Optional) Shall be of type `INTEGER' and of
default kind.
STATUS (Optional) Shall be of type `INTEGER' and of
default kind.
_Return value_:
If COMMAND is present, stores the entire command line that was used
to invoke the program in COMMAND. If LENGTH is present, it is
assigned the length of the command line. If STATUS is present, it
is assigned 0 upon success of the command, -1 if COMMAND is too
short to store the command line, or a positive value in case of an
error.
_Example_:
PROGRAM test_get_command
CHARACTER(len=255) :: cmd
CALL get_command(cmd)
WRITE (*,*) TRIM(cmd)
END PROGRAM
_See also_:
*Note GET_COMMAND_ARGUMENT::, *Note COMMAND_ARGUMENT_COUNT::

File: gfortran.info, Node: GET_COMMAND_ARGUMENT, Next: GETCWD, Prev: GET_COMMAND, Up: Intrinsic Procedures
8.89 `GET_COMMAND_ARGUMENT' -- Get command line arguments
=========================================================
_Description_:
Retrieve the NUMBER-th argument that was passed on the command
line when the containing program was invoked.
_Standard_:
Fortran 2003 and later
_Class_:
Subroutine
_Syntax_:
`CALL GET_COMMAND_ARGUMENT(NUMBER [, VALUE, LENGTH, STATUS])'
_Arguments_:
NUMBER Shall be a scalar of type `INTEGER' and of
default kind, NUMBER \geq 0
VALUE Shall be a scalar of type `CHARACTER' and of
default kind.
LENGTH (Option) Shall be a scalar of type `INTEGER'
and of default kind.
STATUS (Option) Shall be a scalar of type `INTEGER'
and of default kind.
_Return value_:
After `GET_COMMAND_ARGUMENT' returns, the VALUE argument holds the
NUMBER-th command line argument. If VALUE can not hold the
argument, it is truncated to fit the length of VALUE. If there are
less than NUMBER arguments specified at the command line, VALUE
will be filled with blanks. If NUMBER = 0, VALUE is set to the
name of the program (on systems that support this feature). The
LENGTH argument contains the length of the NUMBER-th command line
argument. If the argument retrieval fails, STATUS is a positive
number; if VALUE contains a truncated command line argument,
STATUS is -1; and otherwise the STATUS is zero.
_Example_:
PROGRAM test_get_command_argument
INTEGER :: i
CHARACTER(len=32) :: arg
i = 0
DO
CALL get_command_argument(i, arg)
IF (LEN_TRIM(arg) == 0) EXIT
WRITE (*,*) TRIM(arg)
i = i+1
END DO
END PROGRAM
_See also_:
*Note GET_COMMAND::, *Note COMMAND_ARGUMENT_COUNT::

File: gfortran.info, Node: GETCWD, Next: GETENV, Prev: GET_COMMAND_ARGUMENT, Up: Intrinsic Procedures
8.90 `GETCWD' -- Get current working directory
==============================================
_Description_:
Get current working directory.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL GETCWD(C [, STATUS])'
_Arguments_:
C The type shall be `CHARACTER' and of default
kind.
STATUS (Optional) status flag. Returns 0 on success,
a system specific and nonzero error code
otherwise.
_Example_:
PROGRAM test_getcwd
CHARACTER(len=255) :: cwd
CALL getcwd(cwd)
WRITE(*,*) TRIM(cwd)
END PROGRAM
_See also_:
*Note CHDIR::

File: gfortran.info, Node: GETENV, Next: GET_ENVIRONMENT_VARIABLE, Prev: GETCWD, Up: Intrinsic Procedures
8.91 `GETENV' -- Get an environmental variable
==============================================
_Description_:
Get the VALUE of the environmental variable NAME.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use
of the *Note GET_ENVIRONMENT_VARIABLE:: intrinsic defined by the
Fortran 2003 standard.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL GETENV(NAME, VALUE)'
_Arguments_:
NAME Shall be of type `CHARACTER' and of default
kind.
VALUE Shall be of type `CHARACTER' and of default
kind.
_Return value_:
Stores the value of NAME in VALUE. If VALUE is not large enough to
hold the data, it is truncated. If NAME is not set, VALUE will be
filled with blanks.
_Example_:
PROGRAM test_getenv
CHARACTER(len=255) :: homedir
CALL getenv("HOME", homedir)
WRITE (*,*) TRIM(homedir)
END PROGRAM
_See also_:
*Note GET_ENVIRONMENT_VARIABLE::

File: gfortran.info, Node: GET_ENVIRONMENT_VARIABLE, Next: GETGID, Prev: GETENV, Up: Intrinsic Procedures
8.92 `GET_ENVIRONMENT_VARIABLE' -- Get an environmental variable
================================================================
_Description_:
Get the VALUE of the environmental variable NAME.
_Standard_:
Fortran 2003 and later
_Class_:
Subroutine
_Syntax_:
`CALL GET_ENVIRONMENT_VARIABLE(NAME[, VALUE, LENGTH, STATUS,
TRIM_NAME)'
_Arguments_:
NAME Shall be a scalar of type `CHARACTER' and of
default kind.
VALUE Shall be a scalar of type `CHARACTER' and of
default kind.
LENGTH Shall be a scalar of type `INTEGER' and of
default kind.
STATUS Shall be a scalar of type `INTEGER' and of
default kind.
TRIM_NAME Shall be a scalar of type `LOGICAL' and of
default kind.
_Return value_:
Stores the value of NAME in VALUE. If VALUE is not large enough to
hold the data, it is truncated. If NAME is not set, VALUE will be
filled with blanks. Argument LENGTH contains the length needed for
storing the environment variable NAME or zero if it is not
present. STATUS is -1 if VALUE is present but too short for the
environment variable; it is 1 if the environment variable does not
exist and 2 if the processor does not support environment
variables; in all other cases STATUS is zero. If TRIM_NAME is
present with the value `.FALSE.', the trailing blanks in NAME are
significant; otherwise they are not part of the environment
variable name.
_Example_:
PROGRAM test_getenv
CHARACTER(len=255) :: homedir
CALL get_environment_variable("HOME", homedir)
WRITE (*,*) TRIM(homedir)
END PROGRAM

File: gfortran.info, Node: GETGID, Next: GETLOG, Prev: GET_ENVIRONMENT_VARIABLE, Up: Intrinsic Procedures
8.93 `GETGID' -- Group ID function
==================================
_Description_:
Returns the numerical group ID of the current process.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = GETGID()'
_Return value_:
The return value of `GETGID' is an `INTEGER' of the default kind.
_Example_:
See `GETPID' for an example.
_See also_:
*Note GETPID::, *Note GETUID::

File: gfortran.info, Node: GETLOG, Next: GETPID, Prev: GETGID, Up: Intrinsic Procedures
8.94 `GETLOG' -- Get login name
===============================
_Description_:
Gets the username under which the program is running.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL GETLOG(C)'
_Arguments_:
C Shall be of type `CHARACTER' and of default
kind.
_Return value_:
Stores the current user name in LOGIN. (On systems where POSIX
functions `geteuid' and `getpwuid' are not available, and the
`getlogin' function is not implemented either, this will return a
blank string.)
_Example_:
PROGRAM TEST_GETLOG
CHARACTER(32) :: login
CALL GETLOG(login)
WRITE(*,*) login
END PROGRAM
_See also_:
*Note GETUID::

File: gfortran.info, Node: GETPID, Next: GETUID, Prev: GETLOG, Up: Intrinsic Procedures
8.95 `GETPID' -- Process ID function
====================================
_Description_:
Returns the numerical process identifier of the current process.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = GETPID()'
_Return value_:
The return value of `GETPID' is an `INTEGER' of the default kind.
_Example_:
program info
print *, "The current process ID is ", getpid()
print *, "Your numerical user ID is ", getuid()
print *, "Your numerical group ID is ", getgid()
end program info
_See also_:
*Note GETGID::, *Note GETUID::

File: gfortran.info, Node: GETUID, Next: GMTIME, Prev: GETPID, Up: Intrinsic Procedures
8.96 `GETUID' -- User ID function
=================================
_Description_:
Returns the numerical user ID of the current process.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = GETUID()'
_Return value_:
The return value of `GETUID' is an `INTEGER' of the default kind.
_Example_:
See `GETPID' for an example.
_See also_:
*Note GETPID::, *Note GETLOG::

File: gfortran.info, Node: GMTIME, Next: HOSTNM, Prev: GETUID, Up: Intrinsic Procedures
8.97 `GMTIME' -- Convert time to GMT info
=========================================
_Description_:
Given a system time value TIME (as provided by the `TIME8()'
intrinsic), fills VALUES with values extracted from it appropriate
to the UTC time zone (Universal Coordinated Time, also known in
some countries as GMT, Greenwich Mean Time), using `gmtime(3)'.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL GMTIME(TIME, VALUES)'
_Arguments_:
TIME An `INTEGER' scalar expression corresponding
to a system time, with `INTENT(IN)'.
VALUES A default `INTEGER' array with 9 elements,
with `INTENT(OUT)'.
_Return value_:
The elements of VALUES are assigned as follows:
1. Seconds after the minute, range 0-59 or 0-61 to allow for leap
seconds
2. Minutes after the hour, range 0-59
3. Hours past midnight, range 0-23
4. Day of month, range 0-31
5. Number of months since January, range 0-12
6. Years since 1900
7. Number of days since Sunday, range 0-6
8. Days since January 1
9. Daylight savings indicator: positive if daylight savings is in
effect, zero if not, and negative if the information is not
available.
_See also_:
*Note CTIME::, *Note LTIME::, *Note TIME::, *Note TIME8::

File: gfortran.info, Node: HOSTNM, Next: HUGE, Prev: GMTIME, Up: Intrinsic Procedures
8.98 `HOSTNM' -- Get system host name
=====================================
_Description_:
Retrieves the host name of the system on which the program is
running.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL HOSTNM(C [, STATUS])'
`STATUS = HOSTNM(NAME)'
_Arguments_:
C Shall of type `CHARACTER' and of default kind.
STATUS (Optional) status flag of type `INTEGER'.
Returns 0 on success, or a system specific
error code otherwise.
_Return value_:
In either syntax, NAME is set to the current hostname if it can be
obtained, or to a blank string otherwise.

File: gfortran.info, Node: HUGE, Next: HYPOT, Prev: HOSTNM, Up: Intrinsic Procedures
8.99 `HUGE' -- Largest number of a kind
=======================================
_Description_:
`HUGE(X)' returns the largest number that is not an infinity in
the model of the type of `X'.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = HUGE(X)'
_Arguments_:
X Shall be of type `REAL' or `INTEGER'.
_Return value_:
The return value is of the same type and kind as X
_Example_:
program test_huge_tiny
print *, huge(0), huge(0.0), huge(0.0d0)
print *, tiny(0.0), tiny(0.0d0)
end program test_huge_tiny

File: gfortran.info, Node: HYPOT, Next: IACHAR, Prev: HUGE, Up: Intrinsic Procedures
8.100 `HYPOT' -- Euclidean distance function
============================================
_Description_:
`HYPOT(X,Y)' is the Euclidean distance function. It is equal to
\sqrtX^2 + Y^2, without undue underflow or overflow.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = HYPOT(X, Y)'
_Arguments_:
X The type shall be `REAL'.
Y The type and kind type parameter shall be the
same as X.
_Return value_:
The return value has the same type and kind type parameter as X.
_Example_:
program test_hypot
real(4) :: x = 1.e0_4, y = 0.5e0_4
x = hypot(x,y)
end program test_hypot

File: gfortran.info, Node: IACHAR, Next: IAND, Prev: HYPOT, Up: Intrinsic Procedures
8.101 `IACHAR' -- Code in ASCII collating sequence
==================================================
_Description_:
`IACHAR(C)' returns the code for the ASCII character in the first
character position of `C'.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IACHAR(C [, KIND])'
_Arguments_:
C Shall be a scalar `CHARACTER', with
`INTENT(IN)'
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_Example_:
program test_iachar
integer i
i = iachar(' ')
end program test_iachar
_Note_:
See *Note ICHAR:: for a discussion of converting between numerical
values and formatted string representations.
_See also_:
*Note ACHAR::, *Note CHAR::, *Note ICHAR::

File: gfortran.info, Node: IAND, Next: IARGC, Prev: IACHAR, Up: Intrinsic Procedures
8.102 `IAND' -- Bitwise logical and
===================================
_Description_:
Bitwise logical `AND'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IAND(I, J)'
_Arguments_:
I The type shall be `INTEGER'.
J The type shall be `INTEGER', of the same kind
as I. (As a GNU extension, different kinds
are also permitted.)
_Return value_:
The return type is `INTEGER', of the same kind as the arguments.
(If the argument kinds differ, it is of the same kind as the
larger argument.)
_Example_:
PROGRAM test_iand
INTEGER :: a, b
DATA a / Z'F' /, b / Z'3' /
WRITE (*,*) IAND(a, b)
END PROGRAM
_See also_:
*Note IOR::, *Note IEOR::, *Note IBITS::, *Note IBSET::, *Note
IBCLR::, *Note NOT::

File: gfortran.info, Node: IARGC, Next: IBCLR, Prev: IAND, Up: Intrinsic Procedures
8.103 `IARGC' -- Get the number of command line arguments
=========================================================
_Description_:
`IARGC()' returns the number of arguments passed on the command
line when the containing program was invoked.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use
of the *Note COMMAND_ARGUMENT_COUNT:: intrinsic defined by the
Fortran 2003 standard.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = IARGC()'
_Arguments_:
None.
_Return value_:
The number of command line arguments, type `INTEGER(4)'.
_Example_:
See *Note GETARG::
_See also_:
GNU Fortran 77 compatibility subroutine: *Note GETARG::
Fortran 2003 functions and subroutines: *Note GET_COMMAND::, *Note
GET_COMMAND_ARGUMENT::, *Note COMMAND_ARGUMENT_COUNT::

File: gfortran.info, Node: IBCLR, Next: IBITS, Prev: IARGC, Up: Intrinsic Procedures
8.104 `IBCLR' -- Clear bit
==========================
_Description_:
`IBCLR' returns the value of I with the bit at position POS set to
zero.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IBCLR(I, POS)'
_Arguments_:
I The type shall be `INTEGER'.
POS The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER' and of the same kind as I.
_See also_:
*Note IBITS::, *Note IBSET::, *Note IAND::, *Note IOR::, *Note
IEOR::, *Note MVBITS::

File: gfortran.info, Node: IBITS, Next: IBSET, Prev: IBCLR, Up: Intrinsic Procedures
8.105 `IBITS' -- Bit extraction
===============================
_Description_:
`IBITS' extracts a field of length LEN from I, starting from bit
position POS and extending left for LEN bits. The result is
right-justified and the remaining bits are zeroed. The value of
`POS+LEN' must be less than or equal to the value `BIT_SIZE(I)'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IBITS(I, POS, LEN)'
_Arguments_:
I The type shall be `INTEGER'.
POS The type shall be `INTEGER'.
LEN The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER' and of the same kind as I.
_See also_:
*Note BIT_SIZE::, *Note IBCLR::, *Note IBSET::, *Note IAND::,
*Note IOR::, *Note IEOR::

File: gfortran.info, Node: IBSET, Next: ICHAR, Prev: IBITS, Up: Intrinsic Procedures
8.106 `IBSET' -- Set bit
========================
_Description_:
`IBSET' returns the value of I with the bit at position POS set to
one.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IBSET(I, POS)'
_Arguments_:
I The type shall be `INTEGER'.
POS The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER' and of the same kind as I.
_See also_:
*Note IBCLR::, *Note IBITS::, *Note IAND::, *Note IOR::, *Note
IEOR::, *Note MVBITS::

File: gfortran.info, Node: ICHAR, Next: IDATE, Prev: IBSET, Up: Intrinsic Procedures
8.107 `ICHAR' -- Character-to-integer conversion function
=========================================================
_Description_:
`ICHAR(C)' returns the code for the character in the first
character position of `C' in the system's native character set.
The correspondence between characters and their codes is not
necessarily the same across different GNU Fortran implementations.
_Standard_:
Fortan 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ICHAR(C [, KIND])'
_Arguments_:
C Shall be a scalar `CHARACTER', with
`INTENT(IN)'
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_Example_:
program test_ichar
integer i
i = ichar(' ')
end program test_ichar
_Note_:
No intrinsic exists to convert between a numeric value and a
formatted character string representation - for instance, given the
`CHARACTER' value `'154'', obtaining an `INTEGER' or `REAL' value
with the value 154, or vice versa. Instead, this functionality is
provided by internal-file I/O, as in the following example:
program read_val
integer value
character(len=10) string, string2
string = '154'
! Convert a string to a numeric value
read (string,'(I10)') value
print *, value
! Convert a value to a formatted string
write (string2,'(I10)') value
print *, string2
end program read_val
_See also_:
*Note ACHAR::, *Note CHAR::, *Note IACHAR::

File: gfortran.info, Node: IDATE, Next: IEOR, Prev: ICHAR, Up: Intrinsic Procedures
8.108 `IDATE' -- Get current local time subroutine (day/month/year)
===================================================================
_Description_:
`IDATE(VALUES)' Fills VALUES with the numerical values at the
current local time. The day (in the range 1-31), month (in the
range 1-12), and year appear in elements 1, 2, and 3 of VALUES,
respectively. The year has four significant digits.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL IDATE(VALUES)'
_Arguments_:
VALUES The type shall be `INTEGER, DIMENSION(3)' and
the kind shall be the default integer kind.
_Return value_:
Does not return anything.
_Example_:
program test_idate
integer, dimension(3) :: tarray
call idate(tarray)
print *, tarray(1)
print *, tarray(2)
print *, tarray(3)
end program test_idate

File: gfortran.info, Node: IEOR, Next: IERRNO, Prev: IDATE, Up: Intrinsic Procedures
8.109 `IEOR' -- Bitwise logical exclusive or
============================================
_Description_:
`IEOR' returns the bitwise boolean exclusive-OR of I and J.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IEOR(I, J)'
_Arguments_:
I The type shall be `INTEGER'.
J The type shall be `INTEGER', of the same kind
as I. (As a GNU extension, different kinds
are also permitted.)
_Return value_:
The return type is `INTEGER', of the same kind as the arguments.
(If the argument kinds differ, it is of the same kind as the
larger argument.)
_See also_:
*Note IOR::, *Note IAND::, *Note IBITS::, *Note IBSET::, *Note
IBCLR::, *Note NOT::

File: gfortran.info, Node: IERRNO, Next: INDEX intrinsic, Prev: IEOR, Up: Intrinsic Procedures
8.110 `IERRNO' -- Get the last system error number
==================================================
_Description_:
Returns the last system error number, as given by the C `errno()'
function.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = IERRNO()'
_Arguments_:
None.
_Return value_:
The return value is of type `INTEGER' and of the default integer
kind.
_See also_:
*Note PERROR::

File: gfortran.info, Node: INDEX intrinsic, Next: INT, Prev: IERRNO, Up: Intrinsic Procedures
8.111 `INDEX' -- Position of a substring within a string
========================================================
_Description_:
Returns the position of the start of the first occurrence of string
SUBSTRING as a substring in STRING, counting from one. If
SUBSTRING is not present in STRING, zero is returned. If the BACK
argument is present and true, the return value is the start of the
last occurrence rather than the first.
_Standard_:
Fortran 77 and later, with KIND argument Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = INDEX(STRING, SUBSTRING [, BACK [, KIND]])'
_Arguments_:
STRING Shall be a scalar `CHARACTER', with
`INTENT(IN)'
SUBSTRING Shall be a scalar `CHARACTER', with
`INTENT(IN)'
BACK (Optional) Shall be a scalar `LOGICAL', with
`INTENT(IN)'
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_See also_:
*Note SCAN::, *Note VERIFY::

File: gfortran.info, Node: INT, Next: INT2, Prev: INDEX intrinsic, Up: Intrinsic Procedures
8.112 `INT' -- Convert to integer type
======================================
_Description_:
Convert to integer type
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = INT(A [, KIND))'
_Arguments_:
A Shall be of type `INTEGER', `REAL', or
`COMPLEX'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
These functions return a `INTEGER' variable or array under the
following rules:
(A)
If A is of type `INTEGER', `INT(A) = A'
(B)
If A is of type `REAL' and |A| < 1, `INT(A)' equals `0'. If
|A| \geq 1, then `INT(A)' equals the largest integer that
does not exceed the range of A and whose sign is the same as
the sign of A.
(C)
If A is of type `COMPLEX', rule B is applied to the real part
of A.
_Example_:
program test_int
integer :: i = 42
complex :: z = (-3.7, 1.0)
print *, int(i)
print *, int(z), int(z,8)
end program
_Specific names_:
Name Argument Return type Standard
`IFIX(A)' `REAL(4) A' `INTEGER' Fortran 77 and
later
`IDINT(A)' `REAL(8) A' `INTEGER' Fortran 77 and
later

File: gfortran.info, Node: INT2, Next: INT8, Prev: INT, Up: Intrinsic Procedures
8.113 `INT2' -- Convert to 16-bit integer type
==============================================
_Description_:
Convert to a `KIND=2' integer type. This is equivalent to the
standard `INT' intrinsic with an optional argument of `KIND=2',
and is only included for backwards compatibility.
The `SHORT' intrinsic is equivalent to `INT2'.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = INT2(A)'
_Arguments_:
A Shall be of type `INTEGER', `REAL', or
`COMPLEX'.
_Return value_:
The return value is a `INTEGER(2)' variable.
_See also_:
*Note INT::, *Note INT8::, *Note LONG::

File: gfortran.info, Node: INT8, Next: IOR, Prev: INT2, Up: Intrinsic Procedures
8.114 `INT8' -- Convert to 64-bit integer type
==============================================
_Description_:
Convert to a `KIND=8' integer type. This is equivalent to the
standard `INT' intrinsic with an optional argument of `KIND=8',
and is only included for backwards compatibility.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = INT8(A)'
_Arguments_:
A Shall be of type `INTEGER', `REAL', or
`COMPLEX'.
_Return value_:
The return value is a `INTEGER(8)' variable.
_See also_:
*Note INT::, *Note INT2::, *Note LONG::

File: gfortran.info, Node: IOR, Next: IRAND, Prev: INT8, Up: Intrinsic Procedures
8.115 `IOR' -- Bitwise logical or
=================================
_Description_:
`IOR' returns the bitwise boolean inclusive-OR of I and J.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IOR(I, J)'
_Arguments_:
I The type shall be `INTEGER'.
J The type shall be `INTEGER', of the same kind
as I. (As a GNU extension, different kinds
are also permitted.)
_Return value_:
The return type is `INTEGER', of the same kind as the arguments.
(If the argument kinds differ, it is of the same kind as the
larger argument.)
_See also_:
*Note IEOR::, *Note IAND::, *Note IBITS::, *Note IBSET::, *Note
IBCLR::, *Note NOT::

File: gfortran.info, Node: IRAND, Next: IS_IOSTAT_END, Prev: IOR, Up: Intrinsic Procedures
8.116 `IRAND' -- Integer pseudo-random number
=============================================
_Description_:
`IRAND(FLAG)' returns a pseudo-random number from a uniform
distribution between 0 and a system-dependent limit (which is in
most cases 2147483647). If FLAG is 0, the next number in the
current sequence is returned; if FLAG is 1, the generator is
restarted by `CALL SRAND(0)'; if FLAG has any other value, it is
used as a new seed with `SRAND'.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. It implements a simple modulo generator as provided
by `g77'. For new code, one should consider the use of *Note
RANDOM_NUMBER:: as it implements a superior algorithm.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = IRAND(I)'
_Arguments_:
I Shall be a scalar `INTEGER' of kind 4.
_Return value_:
The return value is of `INTEGER(kind=4)' type.
_Example_:
program test_irand
integer,parameter :: seed = 86456
call srand(seed)
print *, irand(), irand(), irand(), irand()
print *, irand(seed), irand(), irand(), irand()
end program test_irand

File: gfortran.info, Node: IS_IOSTAT_END, Next: IS_IOSTAT_EOR, Prev: IRAND, Up: Intrinsic Procedures
8.117 `IS_IOSTAT_END' -- Test for end-of-file value
===================================================
_Description_:
`IS_IOSTAT_END' tests whether an variable has the value of the I/O
status "end of file". The function is equivalent to comparing the
variable with the `IOSTAT_END' parameter of the intrinsic module
`ISO_FORTRAN_ENV'.
_Standard_:
Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IS_IOSTAT_END(I)'
_Arguments_:
I Shall be of the type `INTEGER'.
_Return value_:
Returns a `LOGICAL' of the default kind, which `.TRUE.' if I has
the value which indicates an end of file condition for IOSTAT=
specifiers, and is `.FALSE.' otherwise.
_Example_:
PROGRAM iostat
IMPLICIT NONE
INTEGER :: stat, i
OPEN(88, FILE='test.dat')
READ(88, *, IOSTAT=stat) i
IF(IS_IOSTAT_END(stat)) STOP 'END OF FILE'
END PROGRAM

File: gfortran.info, Node: IS_IOSTAT_EOR, Next: ISATTY, Prev: IS_IOSTAT_END, Up: Intrinsic Procedures
8.118 `IS_IOSTAT_EOR' -- Test for end-of-record value
=====================================================
_Description_:
`IS_IOSTAT_EOR' tests whether an variable has the value of the I/O
status "end of record". The function is equivalent to comparing the
variable with the `IOSTAT_EOR' parameter of the intrinsic module
`ISO_FORTRAN_ENV'.
_Standard_:
Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = IS_IOSTAT_EOR(I)'
_Arguments_:
I Shall be of the type `INTEGER'.
_Return value_:
Returns a `LOGICAL' of the default kind, which `.TRUE.' if I has
the value which indicates an end of file condition for IOSTAT=
specifiers, and is `.FALSE.' otherwise.
_Example_:
PROGRAM iostat
IMPLICIT NONE
INTEGER :: stat, i(50)
OPEN(88, FILE='test.dat', FORM='UNFORMATTED')
READ(88, IOSTAT=stat) i
IF(IS_IOSTAT_EOR(stat)) STOP 'END OF RECORD'
END PROGRAM

File: gfortran.info, Node: ISATTY, Next: ISHFT, Prev: IS_IOSTAT_EOR, Up: Intrinsic Procedures
8.119 `ISATTY' -- Whether a unit is a terminal device.
======================================================
_Description_:
Determine whether a unit is connected to a terminal device.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = ISATTY(UNIT)'
_Arguments_:
UNIT Shall be a scalar `INTEGER'.
_Return value_:
Returns `.TRUE.' if the UNIT is connected to a terminal device,
`.FALSE.' otherwise.
_Example_:
PROGRAM test_isatty
INTEGER(kind=1) :: unit
DO unit = 1, 10
write(*,*) isatty(unit=unit)
END DO
END PROGRAM
_See also_:
*Note TTYNAM::

File: gfortran.info, Node: ISHFT, Next: ISHFTC, Prev: ISATTY, Up: Intrinsic Procedures
8.120 `ISHFT' -- Shift bits
===========================
_Description_:
`ISHFT' returns a value corresponding to I with all of the bits
shifted SHIFT places. A value of SHIFT greater than zero
corresponds to a left shift, a value of zero corresponds to no
shift, and a value less than zero corresponds to a right shift.
If the absolute value of SHIFT is greater than `BIT_SIZE(I)', the
value is undefined. Bits shifted out from the left end or right
end are lost; zeros are shifted in from the opposite end.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ISHFT(I, SHIFT)'
_Arguments_:
I The type shall be `INTEGER'.
SHIFT The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER' and of the same kind as I.
_See also_:
*Note ISHFTC::

File: gfortran.info, Node: ISHFTC, Next: ISNAN, Prev: ISHFT, Up: Intrinsic Procedures
8.121 `ISHFTC' -- Shift bits circularly
=======================================
_Description_:
`ISHFTC' returns a value corresponding to I with the rightmost
SIZE bits shifted circularly SHIFT places; that is, bits shifted
out one end are shifted into the opposite end. A value of SHIFT
greater than zero corresponds to a left shift, a value of zero
corresponds to no shift, and a value less than zero corresponds to
a right shift. The absolute value of SHIFT must be less than
SIZE. If the SIZE argument is omitted, it is taken to be
equivalent to `BIT_SIZE(I)'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = ISHFTC(I, SHIFT [, SIZE])'
_Arguments_:
I The type shall be `INTEGER'.
SHIFT The type shall be `INTEGER'.
SIZE (Optional) The type shall be `INTEGER'; the
value must be greater than zero and less than
or equal to `BIT_SIZE(I)'.
_Return value_:
The return value is of type `INTEGER' and of the same kind as I.
_See also_:
*Note ISHFT::

File: gfortran.info, Node: ISNAN, Next: ITIME, Prev: ISHFTC, Up: Intrinsic Procedures
8.122 `ISNAN' -- Test for a NaN
===============================
_Description_:
`ISNAN' tests whether a floating-point value is an IEEE
Not-a-Number (NaN).
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`ISNAN(X)'
_Arguments_:
X Variable of the type `REAL'.
_Return value_:
Returns a default-kind `LOGICAL'. The returned value is `TRUE' if
X is a NaN and `FALSE' otherwise.
_Example_:
program test_nan
implicit none
real :: x
x = -1.0
x = sqrt(x)
if (isnan(x)) stop '"x" is a NaN'
end program test_nan

File: gfortran.info, Node: ITIME, Next: KILL, Prev: ISNAN, Up: Intrinsic Procedures
8.123 `ITIME' -- Get current local time subroutine (hour/minutes/seconds)
=========================================================================
_Description_:
`IDATE(VALUES)' Fills VALUES with the numerical values at the
current local time. The hour (in the range 1-24), minute (in the
range 1-60), and seconds (in the range 1-60) appear in elements 1,
2, and 3 of VALUES, respectively.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL ITIME(VALUES)'
_Arguments_:
VALUES The type shall be `INTEGER, DIMENSION(3)' and
the kind shall be the default integer kind.
_Return value_:
Does not return anything.
_Example_:
program test_itime
integer, dimension(3) :: tarray
call itime(tarray)
print *, tarray(1)
print *, tarray(2)
print *, tarray(3)
end program test_itime

File: gfortran.info, Node: KILL, Next: KIND, Prev: ITIME, Up: Intrinsic Procedures
8.124 `KILL' -- Send a signal to a process
==========================================
_Description_:
_Standard_:
Sends the signal specified by SIGNAL to the process PID. See
`kill(2)'.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Class_:
Subroutine, function
_Syntax_:
`CALL KILL(C, VALUE [, STATUS])'
_Arguments_:
C Shall be a scalar `INTEGER', with `INTENT(IN)'
VALUE Shall be a scalar `INTEGER', with `INTENT(IN)'
STATUS (Optional) status flag of type `INTEGER(4)' or
`INTEGER(8)'. Returns 0 on success, or a
system-specific error code otherwise.
_See also_:
*Note ABORT::, *Note EXIT::

File: gfortran.info, Node: KIND, Next: LBOUND, Prev: KILL, Up: Intrinsic Procedures
8.125 `KIND' -- Kind of an entity
=================================
_Description_:
`KIND(X)' returns the kind value of the entity X.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`K = KIND(X)'
_Arguments_:
X Shall be of type `LOGICAL', `INTEGER', `REAL',
`COMPLEX' or `CHARACTER'.
_Return value_:
The return value is a scalar of type `INTEGER' and of the default
integer kind.
_Example_:
program test_kind
integer,parameter :: kc = kind(' ')
integer,parameter :: kl = kind(.true.)
print *, "The default character kind is ", kc
print *, "The default logical kind is ", kl
end program test_kind

File: gfortran.info, Node: LBOUND, Next: LEADZ, Prev: KIND, Up: Intrinsic Procedures
8.126 `LBOUND' -- Lower dimension bounds of an array
====================================================
_Description_:
Returns the lower bounds of an array, or a single lower bound
along the DIM dimension.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = LBOUND(ARRAY [, DIM [, KIND]])'
_Arguments_:
ARRAY Shall be an array, of any type.
DIM (Optional) Shall be a scalar `INTEGER'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind. If DIM is
absent, the result is an array of the lower bounds of ARRAY. If
DIM is present, the result is a scalar corresponding to the lower
bound of the array along that dimension. If ARRAY is an
expression rather than a whole array or array structure component,
or if it has a zero extent along the relevant dimension, the lower
bound is taken to be 1.
_See also_:
*Note UBOUND::

File: gfortran.info, Node: LEADZ, Next: LEN, Prev: LBOUND, Up: Intrinsic Procedures
8.127 `LEADZ' -- Number of leading zero bits of an integer
==========================================================
_Description_:
`LEADZ' returns the number of leading zero bits of an integer.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LEADZ(I)'
_Arguments_:
I Shall be of type `INTEGER'.
_Return value_:
The type of the return value is the default `INTEGER'. If all the
bits of `I' are zero, the result value is `BIT_SIZE(I)'.
_Example_:
PROGRAM test_leadz
WRITE (*,*) LEADZ(1) ! prints 8 if BITSIZE(I) has the value 32
END PROGRAM
_See also_:
*Note BIT_SIZE::, *Note TRAILZ::

File: gfortran.info, Node: LEN, Next: LEN_TRIM, Prev: LEADZ, Up: Intrinsic Procedures
8.128 `LEN' -- Length of a character entity
===========================================
_Description_:
Returns the length of a character string. If STRING is an array,
the length of an element of STRING is returned. Note that STRING
need not be defined when this intrinsic is invoked, since only the
length, not the content, of STRING is needed.
_Standard_:
Fortran 77 and later, with KIND argument Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`L = LEN(STRING [, KIND])'
_Arguments_:
STRING Shall be a scalar or array of type
`CHARACTER', with `INTENT(IN)'
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_See also_:
*Note LEN_TRIM::, *Note ADJUSTL::, *Note ADJUSTR::

File: gfortran.info, Node: LEN_TRIM, Next: LGE, Prev: LEN, Up: Intrinsic Procedures
8.129 `LEN_TRIM' -- Length of a character entity without trailing blank characters
==================================================================================
_Description_:
Returns the length of a character string, ignoring any trailing
blanks.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LEN_TRIM(STRING [, KIND])'
_Arguments_:
STRING Shall be a scalar of type `CHARACTER', with
`INTENT(IN)'
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_See also_:
*Note LEN::, *Note ADJUSTL::, *Note ADJUSTR::

File: gfortran.info, Node: LGE, Next: LGT, Prev: LEN_TRIM, Up: Intrinsic Procedures
8.130 `LGE' -- Lexical greater than or equal
============================================
_Description_:
Determines whether one string is lexically greater than or equal to
another string, where the two strings are interpreted as containing
ASCII character codes. If the String A and String B are not the
same length, the shorter is compared as if spaces were appended to
it to form a value that has the same length as the longer.
In general, the lexical comparison intrinsics `LGE', `LGT', `LLE',
and `LLT' differ from the corresponding intrinsic operators
`.GE.', `.GT.', `.LE.', and `.LT.', in that the latter use the
processor's character ordering (which is not ASCII on some
targets), whereas the former always use the ASCII ordering.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LGE(STRING_A, STRING_B)'
_Arguments_:
STRING_A Shall be of default `CHARACTER' type.
STRING_B Shall be of default `CHARACTER' type.
_Return value_:
Returns `.TRUE.' if `STRING_A >= STRING_B', and `.FALSE.'
otherwise, based on the ASCII ordering.
_See also_:
*Note LGT::, *Note LLE::, *Note LLT::

File: gfortran.info, Node: LGT, Next: LINK, Prev: LGE, Up: Intrinsic Procedures
8.131 `LGT' -- Lexical greater than
===================================
_Description_:
Determines whether one string is lexically greater than another
string, where the two strings are interpreted as containing ASCII
character codes. If the String A and String B are not the same
length, the shorter is compared as if spaces were appended to it
to form a value that has the same length as the longer.
In general, the lexical comparison intrinsics `LGE', `LGT', `LLE',
and `LLT' differ from the corresponding intrinsic operators
`.GE.', `.GT.', `.LE.', and `.LT.', in that the latter use the
processor's character ordering (which is not ASCII on some
targets), whereas the former always use the ASCII ordering.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LGT(STRING_A, STRING_B)'
_Arguments_:
STRING_A Shall be of default `CHARACTER' type.
STRING_B Shall be of default `CHARACTER' type.
_Return value_:
Returns `.TRUE.' if `STRING_A > STRING_B', and `.FALSE.'
otherwise, based on the ASCII ordering.
_See also_:
*Note LGE::, *Note LLE::, *Note LLT::

File: gfortran.info, Node: LINK, Next: LLE, Prev: LGT, Up: Intrinsic Procedures
8.132 `LINK' -- Create a hard link
==================================
_Description_:
Makes a (hard) link from file PATH1 to PATH2. A null character
(`CHAR(0)') can be used to mark the end of the names in PATH1 and
PATH2; otherwise, trailing blanks in the file names are ignored.
If the STATUS argument is supplied, it contains 0 on success or a
nonzero error code upon return; see `link(2)'.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL LINK(PATH1, PATH2 [, STATUS])'
`STATUS = LINK(PATH1, PATH2)'
_Arguments_:
PATH1 Shall be of default `CHARACTER' type.
PATH2 Shall be of default `CHARACTER' type.
STATUS (Optional) Shall be of default `INTEGER' type.
_See also_:
*Note SYMLNK::, *Note UNLINK::

File: gfortran.info, Node: LLE, Next: LLT, Prev: LINK, Up: Intrinsic Procedures
8.133 `LLE' -- Lexical less than or equal
=========================================
_Description_:
Determines whether one string is lexically less than or equal to
another string, where the two strings are interpreted as
containing ASCII character codes. If the String A and String B
are not the same length, the shorter is compared as if spaces were
appended to it to form a value that has the same length as the
longer.
In general, the lexical comparison intrinsics `LGE', `LGT', `LLE',
and `LLT' differ from the corresponding intrinsic operators
`.GE.', `.GT.', `.LE.', and `.LT.', in that the latter use the
processor's character ordering (which is not ASCII on some
targets), whereas the former always use the ASCII ordering.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LLE(STRING_A, STRING_B)'
_Arguments_:
STRING_A Shall be of default `CHARACTER' type.
STRING_B Shall be of default `CHARACTER' type.
_Return value_:
Returns `.TRUE.' if `STRING_A <= STRING_B', and `.FALSE.'
otherwise, based on the ASCII ordering.
_See also_:
*Note LGE::, *Note LGT::, *Note LLT::

File: gfortran.info, Node: LLT, Next: LNBLNK, Prev: LLE, Up: Intrinsic Procedures
8.134 `LLT' -- Lexical less than
================================
_Description_:
Determines whether one string is lexically less than another
string, where the two strings are interpreted as containing ASCII
character codes. If the String A and String B are not the same
length, the shorter is compared as if spaces were appended to it
to form a value that has the same length as the longer.
In general, the lexical comparison intrinsics `LGE', `LGT', `LLE',
and `LLT' differ from the corresponding intrinsic operators
`.GE.', `.GT.', `.LE.', and `.LT.', in that the latter use the
processor's character ordering (which is not ASCII on some
targets), whereas the former always use the ASCII ordering.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LLT(STRING_A, STRING_B)'
_Arguments_:
STRING_A Shall be of default `CHARACTER' type.
STRING_B Shall be of default `CHARACTER' type.
_Return value_:
Returns `.TRUE.' if `STRING_A < STRING_B', and `.FALSE.'
otherwise, based on the ASCII ordering.
_See also_:
*Note LGE::, *Note LGT::, *Note LLE::

File: gfortran.info, Node: LNBLNK, Next: LOC, Prev: LLT, Up: Intrinsic Procedures
8.135 `LNBLNK' -- Index of the last non-blank character in a string
===================================================================
_Description_:
Returns the length of a character string, ignoring any trailing
blanks. This is identical to the standard `LEN_TRIM' intrinsic,
and is only included for backwards compatibility.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = LNBLNK(STRING)'
_Arguments_:
STRING Shall be a scalar of type `CHARACTER', with
`INTENT(IN)'
_Return value_:
The return value is of `INTEGER(kind=4)' type.
_See also_:
*Note INDEX intrinsic::, *Note LEN_TRIM::

File: gfortran.info, Node: LOC, Next: LOG, Prev: LNBLNK, Up: Intrinsic Procedures
8.136 `LOC' -- Returns the address of a variable
================================================
_Description_:
`LOC(X)' returns the address of X as an integer.
_Standard_:
GNU extension
_Class_:
Inquiry function
_Syntax_:
`RESULT = LOC(X)'
_Arguments_:
X Variable of any type.
_Return value_:
The return value is of type `INTEGER', with a `KIND' corresponding
to the size (in bytes) of a memory address on the target machine.
_Example_:
program test_loc
integer :: i
real :: r
i = loc(r)
print *, i
end program test_loc

File: gfortran.info, Node: LOG, Next: LOG10, Prev: LOC, Up: Intrinsic Procedures
8.137 `LOG' -- Logarithm function
=================================
_Description_:
`LOG(X)' computes the logarithm of X.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LOG(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value is of type `REAL' or `COMPLEX'. The kind type
parameter is the same as X. If X is `COMPLEX', the imaginary part
\omega is in the range -\pi \leq \omega \leq \pi.
_Example_:
program test_log
real(8) :: x = 1.0_8
complex :: z = (1.0, 2.0)
x = log(x)
z = log(z)
end program test_log
_Specific names_:
Name Argument Return type Standard
`ALOG(X)' `REAL(4) X' `REAL(4)' f95, gnu
`DLOG(X)' `REAL(8) X' `REAL(8)' f95, gnu
`CLOG(X)' `COMPLEX(4) `COMPLEX(4)' f95, gnu
X'
`ZLOG(X)' `COMPLEX(8) `COMPLEX(8)' f95, gnu
X'
`CDLOG(X)' `COMPLEX(8) `COMPLEX(8)' f95, gnu
X'

File: gfortran.info, Node: LOG10, Next: LOG_GAMMA, Prev: LOG, Up: Intrinsic Procedures
8.138 `LOG10' -- Base 10 logarithm function
===========================================
_Description_:
`LOG10(X)' computes the base 10 logarithm of X.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LOG10(X)'
_Arguments_:
X The type shall be `REAL'.
_Return value_:
The return value is of type `REAL' or `COMPLEX'. The kind type
parameter is the same as X.
_Example_:
program test_log10
real(8) :: x = 10.0_8
x = log10(x)
end program test_log10
_Specific names_:
Name Argument Return type Standard
`ALOG10(X)' `REAL(4) X' `REAL(4)' Fortran 95 and
later
`DLOG10(X)' `REAL(8) X' `REAL(8)' Fortran 95 and
later

File: gfortran.info, Node: LOG_GAMMA, Next: LOGICAL, Prev: LOG10, Up: Intrinsic Procedures
8.139 `LOG_GAMMA' -- Logarithm of the Gamma function
====================================================
_Description_:
`LOG_GAMMA(X)' computes the natural logarithm of the absolute value
of the Gamma (\Gamma) function.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`X = LOG_GAMMA(X)'
_Arguments_:
X Shall be of type `REAL' and neither zero nor a
negative integer.
_Return value_:
The return value is of type `REAL' of the same kind as X.
_Example_:
program test_log_gamma
real :: x = 1.0
x = lgamma(x) ! returns 0.0
end program test_log_gamma
_Specific names_:
Name Argument Return type Standard
`LGAMMA(X)' `REAL(4) X' `REAL(4)' GNU Extension
`ALGAMA(X)' `REAL(4) X' `REAL(4)' GNU Extension
`DLGAMA(X)' `REAL(8) X' `REAL(8)' GNU Extension
_See also_:
Gamma function: *Note GAMMA::

File: gfortran.info, Node: LOGICAL, Next: LONG, Prev: LOG_GAMMA, Up: Intrinsic Procedures
8.140 `LOGICAL' -- Convert to logical type
==========================================
_Description_:
Converts one kind of `LOGICAL' variable to another.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = LOGICAL(L [, KIND])'
_Arguments_:
L The type shall be `LOGICAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is a `LOGICAL' value equal to L, with a kind
corresponding to KIND, or of the default logical kind if KIND is
not given.
_See also_:
*Note INT::, *Note REAL::, *Note CMPLX::

File: gfortran.info, Node: LONG, Next: LSHIFT, Prev: LOGICAL, Up: Intrinsic Procedures
8.141 `LONG' -- Convert to integer type
=======================================
_Description_:
Convert to a `KIND=4' integer type, which is the same size as a C
`long' integer. This is equivalent to the standard `INT'
intrinsic with an optional argument of `KIND=4', and is only
included for backwards compatibility.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = LONG(A)'
_Arguments_:
A Shall be of type `INTEGER', `REAL', or
`COMPLEX'.
_Return value_:
The return value is a `INTEGER(4)' variable.
_See also_:
*Note INT::, *Note INT2::, *Note INT8::

File: gfortran.info, Node: LSHIFT, Next: LSTAT, Prev: LONG, Up: Intrinsic Procedures
8.142 `LSHIFT' -- Left shift bits
=================================
_Description_:
`LSHIFT' returns a value corresponding to I with all of the bits
shifted left by SHIFT places. If the absolute value of SHIFT is
greater than `BIT_SIZE(I)', the value is undefined. Bits shifted
out from the left end are lost; zeros are shifted in from the
opposite end.
This function has been superseded by the `ISHFT' intrinsic, which
is standard in Fortran 95 and later.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = LSHIFT(I, SHIFT)'
_Arguments_:
I The type shall be `INTEGER'.
SHIFT The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER' and of the same kind as I.
_See also_:
*Note ISHFT::, *Note ISHFTC::, *Note RSHIFT::

File: gfortran.info, Node: LSTAT, Next: LTIME, Prev: LSHIFT, Up: Intrinsic Procedures
8.143 `LSTAT' -- Get file status
================================
_Description_:
`LSTAT' is identical to *Note STAT::, except that if path is a
symbolic link, then the link itself is statted, not the file that
it refers to.
The elements in `VALUES' are the same as described by *Note STAT::.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL LSTAT(NAME, VALUES [, STATUS])'
_Arguments_:
NAME The type shall be `CHARACTER' of the default
kind, a valid path within the file system.
VALUES The type shall be `INTEGER(4), DIMENSION(13)'.
STATUS (Optional) status flag of type `INTEGER(4)'.
Returns 0 on success and a system specific
error code otherwise.
_Example_:
See *Note STAT:: for an example.
_See also_:
To stat an open file: *Note FSTAT::, to stat a file: *Note STAT::

File: gfortran.info, Node: LTIME, Next: MALLOC, Prev: LSTAT, Up: Intrinsic Procedures
8.144 `LTIME' -- Convert time to local time info
================================================
_Description_:
Given a system time value TIME (as provided by the `TIME8()'
intrinsic), fills VALUES with values extracted from it appropriate
to the local time zone using `localtime(3)'.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL LTIME(TIME, VALUES)'
_Arguments_:
TIME An `INTEGER' scalar expression corresponding
to a system time, with `INTENT(IN)'.
VALUES A default `INTEGER' array with 9 elements,
with `INTENT(OUT)'.
_Return value_:
The elements of VALUES are assigned as follows:
1. Seconds after the minute, range 0-59 or 0-61 to allow for leap
seconds
2. Minutes after the hour, range 0-59
3. Hours past midnight, range 0-23
4. Day of month, range 0-31
5. Number of months since January, range 0-12
6. Years since 1900
7. Number of days since Sunday, range 0-6
8. Days since January 1
9. Daylight savings indicator: positive if daylight savings is in
effect, zero if not, and negative if the information is not
available.
_See also_:
*Note CTIME::, *Note GMTIME::, *Note TIME::, *Note TIME8::

File: gfortran.info, Node: MALLOC, Next: MATMUL, Prev: LTIME, Up: Intrinsic Procedures
8.145 `MALLOC' -- Allocate dynamic memory
=========================================
_Description_:
`MALLOC(SIZE)' allocates SIZE bytes of dynamic memory and returns
the address of the allocated memory. The `MALLOC' intrinsic is an
extension intended to be used with Cray pointers, and is provided
in GNU Fortran to allow the user to compile legacy code. For new
code using Fortran 95 pointers, the memory allocation intrinsic is
`ALLOCATE'.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`PTR = MALLOC(SIZE)'
_Arguments_:
SIZE The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER(K)', with K such that
variables of type `INTEGER(K)' have the same size as C pointers
(`sizeof(void *)').
_Example_:
The following example demonstrates the use of `MALLOC' and `FREE'
with Cray pointers.
program test_malloc
implicit none
integer i
real*8 x(*), z
pointer(ptr_x,x)
ptr_x = malloc(20*8)
do i = 1, 20
x(i) = sqrt(1.0d0 / i)
end do
z = 0
do i = 1, 20
z = z + x(i)
print *, z
end do
call free(ptr_x)
end program test_malloc
_See also_:
*Note FREE::

File: gfortran.info, Node: MATMUL, Next: MAX, Prev: MALLOC, Up: Intrinsic Procedures
8.146 `MATMUL' -- matrix multiplication
=======================================
_Description_:
Performs a matrix multiplication on numeric or logical arguments.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = MATMUL(MATRIX_A, MATRIX_B)'
_Arguments_:
MATRIX_A An array of `INTEGER', `REAL', `COMPLEX', or
`LOGICAL' type, with a rank of one or two.
MATRIX_B An array of `INTEGER', `REAL', or `COMPLEX'
type if MATRIX_A is of a numeric type;
otherwise, an array of `LOGICAL' type. The
rank shall be one or two, and the first (or
only) dimension of MATRIX_B shall be equal to
the last (or only) dimension of MATRIX_A.
_Return value_:
The matrix product of MATRIX_A and MATRIX_B. The type and kind of
the result follow the usual type and kind promotion rules, as for
the `*' or `.AND.' operators.
_See also_:

File: gfortran.info, Node: MAX, Next: MAXEXPONENT, Prev: MATMUL, Up: Intrinsic Procedures
8.147 `MAX' -- Maximum value of an argument list
================================================
_Description_:
Returns the argument with the largest (most positive) value.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = MAX(A1, A2 [, A3 [, ...]])'
_Arguments_:
A1 The type shall be `INTEGER' or `REAL'.
A2, A3, An expression of the same type and kind as A1.
... (As a GNU extension, arguments of different
kinds are permitted.)
_Return value_:
The return value corresponds to the maximum value among the
arguments, and has the same type and kind as the first argument.
_Specific names_:
Name Argument Return type Standard
`MAX0(I)' `INTEGER(4) `INTEGER(4)' Fortran 77 and
I' later
`AMAX0(I)' `INTEGER(4) `REAL(MAX(X))'Fortran 77 and
I' later
`MAX1(X)' `REAL X' `INT(MAX(X))' Fortran 77 and
later
`AMAX1(X)' `REAL(4) `REAL(4)' Fortran 77 and
X' later
`DMAX1(X)' `REAL(8) `REAL(8)' Fortran 77 and
X' later
_See also_:
*Note MAXLOC:: *Note MAXVAL::, *Note MIN::

File: gfortran.info, Node: MAXEXPONENT, Next: MAXLOC, Prev: MAX, Up: Intrinsic Procedures
8.148 `MAXEXPONENT' -- Maximum exponent of a real kind
======================================================
_Description_:
`MAXEXPONENT(X)' returns the maximum exponent in the model of the
type of `X'.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = MAXEXPONENT(X)'
_Arguments_:
X Shall be of type `REAL'.
_Return value_:
The return value is of type `INTEGER' and of the default integer
kind.
_Example_:
program exponents
real(kind=4) :: x
real(kind=8) :: y
print *, minexponent(x), maxexponent(x)
print *, minexponent(y), maxexponent(y)
end program exponents

File: gfortran.info, Node: MAXLOC, Next: MAXVAL, Prev: MAXEXPONENT, Up: Intrinsic Procedures
8.149 `MAXLOC' -- Location of the maximum value within an array
===============================================================
_Description_:
Determines the location of the element in the array with the
maximum value, or, if the DIM argument is supplied, determines the
locations of the maximum element along each row of the array in the
DIM direction. If MASK is present, only the elements for which
MASK is `.TRUE.' are considered. If more than one element in the
array has the maximum value, the location returned is that of the
first such element in array element order. If the array has zero
size, or all of the elements of MASK are `.FALSE.', then the
result is an array of zeroes. Similarly, if DIM is supplied and
all of the elements of MASK along a given row are zero, the result
value for that row is zero.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = MAXLOC(ARRAY, DIM [, MASK])'
`RESULT = MAXLOC(ARRAY [, MASK])'
_Arguments_:
ARRAY Shall be an array of type `INTEGER' or `REAL'.
DIM (Optional) Shall be a scalar of type
`INTEGER', with a value between one and the
rank of ARRAY, inclusive. It may not be an
optional dummy argument.
MASK Shall be an array of type `LOGICAL', and
conformable with ARRAY.
_Return value_:
If DIM is absent, the result is a rank-one array with a length
equal to the rank of ARRAY. If DIM is present, the result is an
array with a rank one less than the rank of ARRAY, and a size
corresponding to the size of ARRAY with the DIM dimension removed.
If DIM is present and ARRAY has a rank of one, the result is a
scalar. In all cases, the result is of default `INTEGER' type.
_See also_:
*Note MAX::, *Note MAXVAL::

File: gfortran.info, Node: MAXVAL, Next: MCLOCK, Prev: MAXLOC, Up: Intrinsic Procedures
8.150 `MAXVAL' -- Maximum value of an array
===========================================
_Description_:
Determines the maximum value of the elements in an array value,
or, if the DIM argument is supplied, determines the maximum value
along each row of the array in the DIM direction. If MASK is
present, only the elements for which MASK is `.TRUE.' are
considered. If the array has zero size, or all of the elements of
MASK are `.FALSE.', then the result is `-HUGE(ARRAY)' if ARRAY is
numeric, or a string of nulls if ARRAY is of character type.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = MAXVAL(ARRAY, DIM [, MASK])'
`RESULT = MAXVAL(ARRAY [, MASK])'
_Arguments_:
ARRAY Shall be an array of type `INTEGER' or `REAL'.
DIM (Optional) Shall be a scalar of type
`INTEGER', with a value between one and the
rank of ARRAY, inclusive. It may not be an
optional dummy argument.
MASK Shall be an array of type `LOGICAL', and
conformable with ARRAY.
_Return value_:
If DIM is absent, or if ARRAY has a rank of one, the result is a
scalar. If DIM is present, the result is an array with a rank one
less than the rank of ARRAY, and a size corresponding to the size
of ARRAY with the DIM dimension removed. In all cases, the result
is of the same type and kind as ARRAY.
_See also_:
*Note MAX::, *Note MAXLOC::

File: gfortran.info, Node: MCLOCK, Next: MCLOCK8, Prev: MAXVAL, Up: Intrinsic Procedures
8.151 `MCLOCK' -- Time function
===============================
_Description_:
Returns the number of clock ticks since the start of the process,
based on the UNIX function `clock(3)'.
This intrinsic is not fully portable, such as to systems with
32-bit `INTEGER' types but supporting times wider than 32 bits.
Therefore, the values returned by this intrinsic might be, or
become, negative, or numerically less than previous values, during
a single run of the compiled program.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = MCLOCK()'
_Return value_:
The return value is a scalar of type `INTEGER(4)', equal to the
number of clock ticks since the start of the process, or `-1' if
the system does not support `clock(3)'.
_See also_:
*Note CTIME::, *Note GMTIME::, *Note LTIME::, *Note MCLOCK::,
*Note TIME::

File: gfortran.info, Node: MCLOCK8, Next: MERGE, Prev: MCLOCK, Up: Intrinsic Procedures
8.152 `MCLOCK8' -- Time function (64-bit)
=========================================
_Description_:
Returns the number of clock ticks since the start of the process,
based on the UNIX function `clock(3)'.
_Warning:_ this intrinsic does not increase the range of the timing
values over that returned by `clock(3)'. On a system with a 32-bit
`clock(3)', `MCLOCK8()' will return a 32-bit value, even though it
is converted to a 64-bit `INTEGER(8)' value. That means overflows
of the 32-bit value can still occur. Therefore, the values
returned by this intrinsic might be or become negative or
numerically less than previous values during a single run of the
compiled program.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = MCLOCK8()'
_Return value_:
The return value is a scalar of type `INTEGER(8)', equal to the
number of clock ticks since the start of the process, or `-1' if
the system does not support `clock(3)'.
_See also_:
*Note CTIME::, *Note GMTIME::, *Note LTIME::, *Note MCLOCK::,
*Note TIME8::

File: gfortran.info, Node: MERGE, Next: MIN, Prev: MCLOCK8, Up: Intrinsic Procedures
8.153 `MERGE' -- Merge variables
================================
_Description_:
Select values from two arrays according to a logical mask. The
result is equal to TSOURCE if MASK is `.TRUE.', or equal to
FSOURCE if it is `.FALSE.'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = MERGE(TSOURCE, FSOURCE, MASK)'
_Arguments_:
TSOURCE May be of any type.
FSOURCE Shall be of the same type and type parameters
as TSOURCE.
MASK Shall be of type `LOGICAL'.
_Return value_:
The result is of the same type and type parameters as TSOURCE.

File: gfortran.info, Node: MIN, Next: MINEXPONENT, Prev: MERGE, Up: Intrinsic Procedures
8.154 `MIN' -- Minimum value of an argument list
================================================
_Description_:
Returns the argument with the smallest (most negative) value.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = MIN(A1, A2 [, A3, ...])'
_Arguments_:
A1 The type shall be `INTEGER' or `REAL'.
A2, A3, An expression of the same type and kind as A1.
... (As a GNU extension, arguments of different
kinds are permitted.)
_Return value_:
The return value corresponds to the maximum value among the
arguments, and has the same type and kind as the first argument.
_Specific names_:
Name Argument Return type Standard
`MIN0(I)' `INTEGER(4) `INTEGER(4)' Fortran 77 and
I' later
`AMIN0(I)' `INTEGER(4) `REAL(MIN(X))'Fortran 77 and
I' later
`MIN1(X)' `REAL X' `INT(MIN(X))' Fortran 77 and
later
`AMIN1(X)' `REAL(4) `REAL(4)' Fortran 77 and
X' later
`DMIN1(X)' `REAL(8) `REAL(8)' Fortran 77 and
X' later
_See also_:
*Note MAX::, *Note MINLOC::, *Note MINVAL::

File: gfortran.info, Node: MINEXPONENT, Next: MINLOC, Prev: MIN, Up: Intrinsic Procedures
8.155 `MINEXPONENT' -- Minimum exponent of a real kind
======================================================
_Description_:
`MINEXPONENT(X)' returns the minimum exponent in the model of the
type of `X'.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = MINEXPONENT(X)'
_Arguments_:
X Shall be of type `REAL'.
_Return value_:
The return value is of type `INTEGER' and of the default integer
kind.
_Example_:
See `MAXEXPONENT' for an example.

File: gfortran.info, Node: MINLOC, Next: MINVAL, Prev: MINEXPONENT, Up: Intrinsic Procedures
8.156 `MINLOC' -- Location of the minimum value within an array
===============================================================
_Description_:
Determines the location of the element in the array with the
minimum value, or, if the DIM argument is supplied, determines the
locations of the minimum element along each row of the array in the
DIM direction. If MASK is present, only the elements for which
MASK is `.TRUE.' are considered. If more than one element in the
array has the minimum value, the location returned is that of the
first such element in array element order. If the array has zero
size, or all of the elements of MASK are `.FALSE.', then the
result is an array of zeroes. Similarly, if DIM is supplied and
all of the elements of MASK along a given row are zero, the result
value for that row is zero.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = MINLOC(ARRAY, DIM [, MASK])'
`RESULT = MINLOC(ARRAY [, MASK])'
_Arguments_:
ARRAY Shall be an array of type `INTEGER' or `REAL'.
DIM (Optional) Shall be a scalar of type
`INTEGER', with a value between one and the
rank of ARRAY, inclusive. It may not be an
optional dummy argument.
MASK Shall be an array of type `LOGICAL', and
conformable with ARRAY.
_Return value_:
If DIM is absent, the result is a rank-one array with a length
equal to the rank of ARRAY. If DIM is present, the result is an
array with a rank one less than the rank of ARRAY, and a size
corresponding to the size of ARRAY with the DIM dimension removed.
If DIM is present and ARRAY has a rank of one, the result is a
scalar. In all cases, the result is of default `INTEGER' type.
_See also_:
*Note MIN::, *Note MINVAL::

File: gfortran.info, Node: MINVAL, Next: MOD, Prev: MINLOC, Up: Intrinsic Procedures
8.157 `MINVAL' -- Minimum value of an array
===========================================
_Description_:
Determines the minimum value of the elements in an array value,
or, if the DIM argument is supplied, determines the minimum value
along each row of the array in the DIM direction. If MASK is
present, only the elements for which MASK is `.TRUE.' are
considered. If the array has zero size, or all of the elements of
MASK are `.FALSE.', then the result is `HUGE(ARRAY)' if ARRAY is
numeric, or a string of `CHAR(255)' characters if ARRAY is of
character type.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = MINVAL(ARRAY, DIM [, MASK])'
`RESULT = MINVAL(ARRAY [, MASK])'
_Arguments_:
ARRAY Shall be an array of type `INTEGER' or `REAL'.
DIM (Optional) Shall be a scalar of type
`INTEGER', with a value between one and the
rank of ARRAY, inclusive. It may not be an
optional dummy argument.
MASK Shall be an array of type `LOGICAL', and
conformable with ARRAY.
_Return value_:
If DIM is absent, or if ARRAY has a rank of one, the result is a
scalar. If DIM is present, the result is an array with a rank one
less than the rank of ARRAY, and a size corresponding to the size
of ARRAY with the DIM dimension removed. In all cases, the result
is of the same type and kind as ARRAY.
_See also_:
*Note MIN::, *Note MINLOC::

File: gfortran.info, Node: MOD, Next: MODULO, Prev: MINVAL, Up: Intrinsic Procedures
8.158 `MOD' -- Remainder function
=================================
_Description_:
`MOD(A,P)' computes the remainder of the division of A by P. It is
calculated as `A - (INT(A/P) * P)'.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = MOD(A, P)'
_Arguments_:
A Shall be a scalar of type `INTEGER' or `REAL'
P Shall be a scalar of the same type as A and not
equal to zero
_Return value_:
The kind of the return value is the result of cross-promoting the
kinds of the arguments.
_Example_:
program test_mod
print *, mod(17,3)
print *, mod(17.5,5.5)
print *, mod(17.5d0,5.5)
print *, mod(17.5,5.5d0)
print *, mod(-17,3)
print *, mod(-17.5,5.5)
print *, mod(-17.5d0,5.5)
print *, mod(-17.5,5.5d0)
print *, mod(17,-3)
print *, mod(17.5,-5.5)
print *, mod(17.5d0,-5.5)
print *, mod(17.5,-5.5d0)
end program test_mod
_Specific names_:
Name Arguments Return type Standard
`AMOD(A,P)' `REAL(4)' `REAL(4)' Fortran 95 and
later
`DMOD(A,P)' `REAL(8)' `REAL(8)' Fortran 95 and
later

File: gfortran.info, Node: MODULO, Next: MOVE_ALLOC, Prev: MOD, Up: Intrinsic Procedures
8.159 `MODULO' -- Modulo function
=================================
_Description_:
`MODULO(A,P)' computes the A modulo P.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = MODULO(A, P)'
_Arguments_:
A Shall be a scalar of type `INTEGER' or `REAL'
P Shall be a scalar of the same type and kind as
A
_Return value_:
The type and kind of the result are those of the arguments.
If A and P are of type `INTEGER':
`MODULO(A,P)' has the value R such that `A=Q*P+R', where Q is
an integer and R is between 0 (inclusive) and P (exclusive).
If A and P are of type `REAL':
`MODULO(A,P)' has the value of `A - FLOOR (A / P) * P'.
In all cases, if P is zero the result is processor-dependent.
_Example_:
program test_modulo
print *, modulo(17,3)
print *, modulo(17.5,5.5)
print *, modulo(-17,3)
print *, modulo(-17.5,5.5)
print *, modulo(17,-3)
print *, modulo(17.5,-5.5)
end program

File: gfortran.info, Node: MOVE_ALLOC, Next: MVBITS, Prev: MODULO, Up: Intrinsic Procedures
8.160 `MOVE_ALLOC' -- Move allocation from one object to another
================================================================
_Description_:
`MOVE_ALLOC(FROM, TO)' moves the allocation from FROM to TO. FROM
will become deallocated in the process.
_Standard_:
Fortran 2003 and later
_Class_:
Subroutine
_Syntax_:
`CALL MOVE_ALLOC(FROM, TO)'
_Arguments_:
FROM `ALLOCATABLE', `INTENT(INOUT)', may be of any
type and kind.
TO `ALLOCATABLE', `INTENT(OUT)', shall be of the
same type, kind and rank as FROM.
_Return value_:
None
_Example_:
program test_move_alloc
integer, allocatable :: a(:), b(:)
allocate(a(3))
a = [ 1, 2, 3 ]
call move_alloc(a, b)
print *, allocated(a), allocated(b)
print *, b
end program test_move_alloc

File: gfortran.info, Node: MVBITS, Next: NEAREST, Prev: MOVE_ALLOC, Up: Intrinsic Procedures
8.161 `MVBITS' -- Move bits from one integer to another
=======================================================
_Description_:
Moves LEN bits from positions FROMPOS through `FROMPOS+LEN-1' of
FROM to positions TOPOS through `TOPOS+LEN-1' of TO. The portion
of argument TO not affected by the movement of bits is unchanged.
The values of `FROMPOS+LEN-1' and `TOPOS+LEN-1' must be less than
`BIT_SIZE(FROM)'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental subroutine
_Syntax_:
`CALL MVBITS(FROM, FROMPOS, LEN, TO, TOPOS)'
_Arguments_:
FROM The type shall be `INTEGER'.
FROMPOS The type shall be `INTEGER'.
LEN The type shall be `INTEGER'.
TO The type shall be `INTEGER', of the same kind
as FROM.
TOPOS The type shall be `INTEGER'.
_See also_:
*Note IBCLR::, *Note IBSET::, *Note IBITS::, *Note IAND::, *Note
IOR::, *Note IEOR::

File: gfortran.info, Node: NEAREST, Next: NEW_LINE, Prev: MVBITS, Up: Intrinsic Procedures
8.162 `NEAREST' -- Nearest representable number
===============================================
_Description_:
`NEAREST(X, S)' returns the processor-representable number nearest
to `X' in the direction indicated by the sign of `S'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = NEAREST(X, S)'
_Arguments_:
X Shall be of type `REAL'.
S (Optional) shall be of type `REAL' and not
equal to zero.
_Return value_:
The return value is of the same type as `X'. If `S' is positive,
`NEAREST' returns the processor-representable number greater than
`X' and nearest to it. If `S' is negative, `NEAREST' returns the
processor-representable number smaller than `X' and nearest to it.
_Example_:
program test_nearest
real :: x, y
x = nearest(42.0, 1.0)
y = nearest(42.0, -1.0)
write (*,"(3(G20.15))") x, y, x - y
end program test_nearest

File: gfortran.info, Node: NEW_LINE, Next: NINT, Prev: NEAREST, Up: Intrinsic Procedures
8.163 `NEW_LINE' -- New line character
======================================
_Description_:
`NEW_LINE(C)' returns the new-line character.
_Standard_:
Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = NEW_LINE(C)'
_Arguments_:
C The argument shall be a scalar or array of the
type `CHARACTER'.
_Return value_:
Returns a CHARACTER scalar of length one with the new-line
character of the same kind as parameter C.
_Example_:
program newline
implicit none
write(*,'(A)') 'This is record 1.'//NEW_LINE('A')//'This is record 2.'
end program newline

File: gfortran.info, Node: NINT, Next: NOT, Prev: NEW_LINE, Up: Intrinsic Procedures
8.164 `NINT' -- Nearest whole number
====================================
_Description_:
`NINT(A)' rounds its argument to the nearest whole number.
_Standard_:
Fortran 77 and later, with KIND argument Fortran 90 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = NINT(A [, KIND])'
_Arguments_:
A The type of the argument shall be `REAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
Returns A with the fractional portion of its magnitude eliminated
by rounding to the nearest whole number and with its sign
preserved, converted to an `INTEGER' of the default kind.
_Example_:
program test_nint
real(4) x4
real(8) x8
x4 = 1.234E0_4
x8 = 4.321_8
print *, nint(x4), idnint(x8)
end program test_nint
_Specific names_:
Name Argument Standard
`IDNINT(X)' `REAL(8)' Fortran 95 and
later
_See also_:
*Note CEILING::, *Note FLOOR::

File: gfortran.info, Node: NOT, Next: NULL, Prev: NINT, Up: Intrinsic Procedures
8.165 `NOT' -- Logical negation
===============================
_Description_:
`NOT' returns the bitwise boolean inverse of I.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = NOT(I)'
_Arguments_:
I The type shall be `INTEGER'.
_Return value_:
The return type is `INTEGER', of the same kind as the argument.
_See also_:
*Note IAND::, *Note IEOR::, *Note IOR::, *Note IBITS::, *Note
IBSET::, *Note IBCLR::

File: gfortran.info, Node: NULL, Next: OR, Prev: NOT, Up: Intrinsic Procedures
8.166 `NULL' -- Function that returns an disassociated pointer
==============================================================
_Description_:
Returns a disassociated pointer.
If MOLD is present, a dissassociated pointer of the same type is
returned, otherwise the type is determined by context.
In Fortran 95, MOLD is optional. Please note that Fortran 2003
includes cases where it is required.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`PTR => NULL([MOLD])'
_Arguments_:
MOLD (Optional) shall be a pointer of any
association status and of any type.
_Return value_:
A disassociated pointer.
_Example_:
REAL, POINTER, DIMENSION(:) :: VEC => NULL ()
_See also_:
*Note ASSOCIATED::

File: gfortran.info, Node: OR, Next: PACK, Prev: NULL, Up: Intrinsic Procedures
8.167 `OR' -- Bitwise logical OR
================================
_Description_:
Bitwise logical `OR'.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. For integer arguments, programmers should consider
the use of the *Note IOR:: intrinsic defined by the Fortran
standard.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = OR(I, J)'
_Arguments_:
I The type shall be either a scalar `INTEGER'
type or a scalar `LOGICAL' type.
J The type shall be the same as the type of J.
_Return value_:
The return type is either a scalar `INTEGER' or a scalar
`LOGICAL'. If the kind type parameters differ, then the smaller
kind type is implicitly converted to larger kind, and the return
has the larger kind.
_Example_:
PROGRAM test_or
LOGICAL :: T = .TRUE., F = .FALSE.
INTEGER :: a, b
DATA a / Z'F' /, b / Z'3' /
WRITE (*,*) OR(T, T), OR(T, F), OR(F, T), OR(F, F)
WRITE (*,*) OR(a, b)
END PROGRAM
_See also_:
Fortran 95 elemental function: *Note IOR::

File: gfortran.info, Node: PACK, Next: PERROR, Prev: OR, Up: Intrinsic Procedures
8.168 `PACK' -- Pack an array into an array of rank one
=======================================================
_Description_:
Stores the elements of ARRAY in an array of rank one.
The beginning of the resulting array is made up of elements whose
MASK equals `TRUE'. Afterwards, positions are filled with elements
taken from VECTOR.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = PACK(ARRAY, MASK[,VECTOR]'
_Arguments_:
ARRAY Shall be an array of any type.
MASK Shall be an array of type `LOGICAL' and of the
same size as ARRAY. Alternatively, it may be a
`LOGICAL' scalar.
VECTOR (Optional) shall be an array of the same type
as ARRAY and of rank one. If present, the
number of elements in VECTOR shall be equal to
or greater than the number of true elements in
MASK. If MASK is scalar, the number of
elements in VECTOR shall be equal to or
greater than the number of elements in ARRAY.
_Return value_:
The result is an array of rank one and the same type as that of
ARRAY. If VECTOR is present, the result size is that of VECTOR,
the number of `TRUE' values in MASK otherwise.
_Example_:
Gathering nonzero elements from an array:
PROGRAM test_pack_1
INTEGER :: m(6)
m = (/ 1, 0, 0, 0, 5, 0 /)
WRITE(*, FMT="(6(I0, ' '))") pack(m, m /= 0) ! "1 5"
END PROGRAM
Gathering nonzero elements from an array and appending elements
from VECTOR:
PROGRAM test_pack_2
INTEGER :: m(4)
m = (/ 1, 0, 0, 2 /)
WRITE(*, FMT="(4(I0, ' '))") pack(m, m /= 0, (/ 0, 0, 3, 4 /)) ! "1 2 3 4"
END PROGRAM
_See also_:
*Note UNPACK::

File: gfortran.info, Node: PERROR, Next: PRECISION, Prev: PACK, Up: Intrinsic Procedures
8.169 `PERROR' -- Print system error message
============================================
_Description_:
Prints (on the C `stderr' stream) a newline-terminated error
message corresponding to the last system error. This is prefixed by
STRING, a colon and a space. See `perror(3)'.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL PERROR(STRING)'
_Arguments_:
STRING A scalar of type `CHARACTER' and of the
default kind.
_See also_:
*Note IERRNO::

File: gfortran.info, Node: PRECISION, Next: PRESENT, Prev: PERROR, Up: Intrinsic Procedures
8.170 `PRECISION' -- Decimal precision of a real kind
=====================================================
_Description_:
`PRECISION(X)' returns the decimal precision in the model of the
type of `X'.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = PRECISION(X)'
_Arguments_:
X Shall be of type `REAL' or `COMPLEX'.
_Return value_:
The return value is of type `INTEGER' and of the default integer
kind.
_Example_:
program prec_and_range
real(kind=4) :: x(2)
complex(kind=8) :: y
print *, precision(x), range(x)
print *, precision(y), range(y)
end program prec_and_range

File: gfortran.info, Node: PRESENT, Next: PRODUCT, Prev: PRECISION, Up: Intrinsic Procedures
8.171 `PRESENT' -- Determine whether an optional dummy argument is specified
============================================================================
_Description_:
Determines whether an optional dummy argument is present.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = PRESENT(A)'
_Arguments_:
A May be of any type and may be a pointer,
scalar or array value, or a dummy procedure.
It shall be the name of an optional dummy
argument accessible within the current
subroutine or function.
_Return value_:
Returns either `TRUE' if the optional argument A is present, or
`FALSE' otherwise.
_Example_:
PROGRAM test_present
WRITE(*,*) f(), f(42) ! "F T"
CONTAINS
LOGICAL FUNCTION f(x)
INTEGER, INTENT(IN), OPTIONAL :: x
f = PRESENT(x)
END FUNCTION
END PROGRAM

File: gfortran.info, Node: PRODUCT, Next: RADIX, Prev: PRESENT, Up: Intrinsic Procedures
8.172 `PRODUCT' -- Product of array elements
============================================
_Description_:
Multiplies the elements of ARRAY along dimension DIM if the
corresponding element in MASK is `TRUE'.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = PRODUCT(ARRAY[, MASK])'
`RESULT = PRODUCT(ARRAY, DIM[, MASK])'
_Arguments_:
ARRAY Shall be an array of type `INTEGER', `REAL' or
`COMPLEX'.
DIM (Optional) shall be a scalar of type `INTEGER'
with a value in the range from 1 to n, where n
equals the rank of ARRAY.
MASK (Optional) shall be of type `LOGICAL' and
either be a scalar or an array of the same
shape as ARRAY.
_Return value_:
The result is of the same type as ARRAY.
If DIM is absent, a scalar with the product of all elements in
ARRAY is returned. Otherwise, an array of rank n-1, where n equals
the rank of ARRAY, and a shape similar to that of ARRAY with
dimension DIM dropped is returned.
_Example_:
PROGRAM test_product
INTEGER :: x(5) = (/ 1, 2, 3, 4 ,5 /)
print *, PRODUCT(x) ! all elements, product = 120
print *, PRODUCT(x, MASK=MOD(x, 2)==1) ! odd elements, product = 15
END PROGRAM
_See also_:
*Note SUM::

File: gfortran.info, Node: RADIX, Next: RANDOM_NUMBER, Prev: PRODUCT, Up: Intrinsic Procedures
8.173 `RADIX' -- Base of a model number
=======================================
_Description_:
`RADIX(X)' returns the base of the model representing the entity X.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = RADIX(X)'
_Arguments_:
X Shall be of type `INTEGER' or `REAL'
_Return value_:
The return value is a scalar of type `INTEGER' and of the default
integer kind.
_Example_:
program test_radix
print *, "The radix for the default integer kind is", radix(0)
print *, "The radix for the default real kind is", radix(0.0)
end program test_radix

File: gfortran.info, Node: RAN, Next: REAL, Prev: RANGE, Up: Intrinsic Procedures
8.174 `RAN' -- Real pseudo-random number
========================================
_Description_:
For compatibility with HP FORTRAN 77/iX, the `RAN' intrinsic is
provided as an alias for `RAND'. See *Note RAND:: for complete
documentation.
_Standard_:
GNU extension
_Class_:
Function
_See also_:
*Note RAND::, *Note RANDOM_NUMBER::

File: gfortran.info, Node: RAND, Next: RANGE, Prev: RANDOM_SEED, Up: Intrinsic Procedures
8.175 `RAND' -- Real pseudo-random number
=========================================
_Description_:
`RAND(FLAG)' returns a pseudo-random number from a uniform
distribution between 0 and 1. If FLAG is 0, the next number in the
current sequence is returned; if FLAG is 1, the generator is
restarted by `CALL SRAND(0)'; if FLAG has any other value, it is
used as a new seed with `SRAND'.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. It implements a simple modulo generator as provided
by `g77'. For new code, one should consider the use of *Note
RANDOM_NUMBER:: as it implements a superior algorithm.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = RAND(I)'
_Arguments_:
I Shall be a scalar `INTEGER' of kind 4.
_Return value_:
The return value is of `REAL' type and the default kind.
_Example_:
program test_rand
integer,parameter :: seed = 86456
call srand(seed)
print *, rand(), rand(), rand(), rand()
print *, rand(seed), rand(), rand(), rand()
end program test_rand
_See also_:
*Note SRAND::, *Note RANDOM_NUMBER::

File: gfortran.info, Node: RANDOM_NUMBER, Next: RANDOM_SEED, Prev: RADIX, Up: Intrinsic Procedures
8.176 `RANDOM_NUMBER' -- Pseudo-random number
=============================================
_Description_:
Returns a single pseudorandom number or an array of pseudorandom
numbers from the uniform distribution over the range 0 \leq x < 1.
The runtime-library implements George Marsaglia's KISS (Keep It
Simple Stupid) random number generator (RNG). This RNG combines:
1. The congruential generator x(n) = 69069 \cdot x(n-1) +
1327217885 with a period of 2^32,
2. A 3-shift shift-register generator with a period of 2^32 - 1,
3. Two 16-bit multiply-with-carry generators with a period of
597273182964842497 > 2^59.
The overall period exceeds 2^123.
Please note, this RNG is thread safe if used within OpenMP
directives, i.e., its state will be consistent while called from
multiple threads. However, the KISS generator does not create
random numbers in parallel from multiple sources, but in sequence
from a single source. If an OpenMP-enabled application heavily
relies on random numbers, one should consider employing a
dedicated parallel random number generator instead.
_Standard_:
Fortran 95 and later
_Class_:
Subroutine
_Syntax_:
`RANDOM_NUMBER(HARVEST)'
_Arguments_:
HARVEST Shall be a scalar or an array of type `REAL'.
_Example_:
program test_random_number
REAL :: r(5,5)
CALL init_random_seed() ! see example of RANDOM_SEED
CALL RANDOM_NUMBER(r)
end program
_See also_:
*Note RANDOM_SEED::

File: gfortran.info, Node: RANDOM_SEED, Next: RAND, Prev: RANDOM_NUMBER, Up: Intrinsic Procedures
8.177 `RANDOM_SEED' -- Initialize a pseudo-random number sequence
=================================================================
_Description_:
Restarts or queries the state of the pseudorandom number generator
used by `RANDOM_NUMBER'.
If `RANDOM_SEED' is called without arguments, it is initialized to
a default state. The example below shows how to initialize the
random seed based on the system's time.
_Standard_:
Fortran 95 and later
_Class_:
Subroutine
_Syntax_:
`CALL RANDOM_SEED([SIZE, PUT, GET])'
_Arguments_:
SIZE (Optional) Shall be a scalar and of type
default `INTEGER', with `INTENT(OUT)'. It
specifies the minimum size of the arrays used
with the PUT and GET arguments.
PUT (Optional) Shall be an array of type default
`INTEGER' and rank one. It is `INTENT(IN)' and
the size of the array must be larger than or
equal to the number returned by the SIZE
argument.
GET (Optional) Shall be an array of type default
`INTEGER' and rank one. It is `INTENT(OUT)'
and the size of the array must be larger than
or equal to the number returned by the SIZE
argument.
_Example_:
SUBROUTINE init_random_seed()
INTEGER :: i, n, clock
INTEGER, DIMENSION(:), ALLOCATABLE :: seed
CALL RANDOM_SEED(size = n)
ALLOCATE(seed(n))
CALL SYSTEM_CLOCK(COUNT=clock)
seed = clock + 37 * (/ (i - 1, i = 1, n) /)
CALL RANDOM_SEED(PUT = seed)
DEALLOCATE(seed)
END SUBROUTINE
_See also_:
*Note RANDOM_NUMBER::

File: gfortran.info, Node: RANGE, Next: RAN, Prev: RAND, Up: Intrinsic Procedures
8.178 `RANGE' -- Decimal exponent range
=======================================
_Description_:
`RANGE(X)' returns the decimal exponent range in the model of the
type of `X'.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = RANGE(X)'
_Arguments_:
X Shall be of type `INTEGER', `REAL' or
`COMPLEX'.
_Return value_:
The return value is of type `INTEGER' and of the default integer
kind.
_Example_:
See `PRECISION' for an example.

File: gfortran.info, Node: REAL, Next: RENAME, Prev: RAN, Up: Intrinsic Procedures
8.179 `REAL' -- Convert to real type
====================================
_Description_:
`REAL(A [, KIND])' converts its argument A to a real type. The
`REALPART' function is provided for compatibility with `g77', and
its use is strongly discouraged.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = REAL(A [, KIND])'
`RESULT = REALPART(Z)'
_Arguments_:
A Shall be `INTEGER', `REAL', or `COMPLEX'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
These functions return a `REAL' variable or array under the
following rules:
(A)
`REAL(A)' is converted to a default real type if A is an
integer or real variable.
(B)
`REAL(A)' is converted to a real type with the kind type
parameter of A if A is a complex variable.
(C)
`REAL(A, KIND)' is converted to a real type with kind type
parameter KIND if A is a complex, integer, or real variable.
_Example_:
program test_real
complex :: x = (1.0, 2.0)
print *, real(x), real(x,8), realpart(x)
end program test_real
_See also_:
*Note DBLE::, *Note DFLOAT::, *Note FLOAT::

File: gfortran.info, Node: RENAME, Next: REPEAT, Prev: REAL, Up: Intrinsic Procedures
8.180 `RENAME' -- Rename a file
===============================
_Description_:
Renames a file from file PATH1 to PATH2. A null character
(`CHAR(0)') can be used to mark the end of the names in PATH1 and
PATH2; otherwise, trailing blanks in the file names are ignored.
If the STATUS argument is supplied, it contains 0 on success or a
nonzero error code upon return; see `rename(2)'.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL RENAME(PATH1, PATH2 [, STATUS])'
`STATUS = RENAME(PATH1, PATH2)'
_Arguments_:
PATH1 Shall be of default `CHARACTER' type.
PATH2 Shall be of default `CHARACTER' type.
STATUS (Optional) Shall be of default `INTEGER' type.
_See also_:
*Note LINK::

File: gfortran.info, Node: REPEAT, Next: RESHAPE, Prev: RENAME, Up: Intrinsic Procedures
8.181 `REPEAT' -- Repeated string concatenation
===============================================
_Description_:
Concatenates NCOPIES copies of a string.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = REPEAT(STRING, NCOPIES)'
_Arguments_:
STRING Shall be scalar and of type `CHARACTER'.
NCOPIES Shall be scalar and of type `INTEGER'.
_Return value_:
A new scalar of type `CHARACTER' built up from NCOPIES copies of
STRING.
_Example_:
program test_repeat
write(*,*) repeat("x", 5) ! "xxxxx"
end program

File: gfortran.info, Node: RESHAPE, Next: RRSPACING, Prev: REPEAT, Up: Intrinsic Procedures
8.182 `RESHAPE' -- Function to reshape an array
===============================================
_Description_:
Reshapes SOURCE to correspond to SHAPE. If necessary, the new
array may be padded with elements from PAD or permuted as defined
by ORDER.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = RESHAPE(SOURCE, SHAPE[, PAD, ORDER])'
_Arguments_:
SOURCE Shall be an array of any type.
SHAPE Shall be of type `INTEGER' and an array of
rank one. Its values must be positive or zero.
PAD (Optional) shall be an array of the same type
as SOURCE.
ORDER (Optional) shall be of type `INTEGER' and an
array of the same shape as SHAPE. Its values
shall be a permutation of the numbers from 1
to n, where n is the size of SHAPE. If ORDER
is absent, the natural ordering shall be
assumed.
_Return value_:
The result is an array of shape SHAPE with the same type as SOURCE.
_Example_:
PROGRAM test_reshape
INTEGER, DIMENSION(4) :: x
WRITE(*,*) SHAPE(x) ! prints "4"
WRITE(*,*) SHAPE(RESHAPE(x, (/2, 2/))) ! prints "2 2"
END PROGRAM
_See also_:
*Note SHAPE::

File: gfortran.info, Node: RRSPACING, Next: RSHIFT, Prev: RESHAPE, Up: Intrinsic Procedures
8.183 `RRSPACING' -- Reciprocal of the relative spacing
=======================================================
_Description_:
`RRSPACING(X)' returns the reciprocal of the relative spacing of
model numbers near X.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = RRSPACING(X)'
_Arguments_:
X Shall be of type `REAL'.
_Return value_:
The return value is of the same type and kind as X. The value
returned is equal to `ABS(FRACTION(X)) *
FLOAT(RADIX(X))**DIGITS(X)'.
_See also_:
*Note SPACING::

File: gfortran.info, Node: RSHIFT, Next: SCALE, Prev: RRSPACING, Up: Intrinsic Procedures
8.184 `RSHIFT' -- Right shift bits
==================================
_Description_:
`RSHIFT' returns a value corresponding to I with all of the bits
shifted right by SHIFT places. If the absolute value of SHIFT is
greater than `BIT_SIZE(I)', the value is undefined. Bits shifted
out from the left end are lost; zeros are shifted in from the
opposite end.
This function has been superseded by the `ISHFT' intrinsic, which
is standard in Fortran 95 and later.
_Standard_:
GNU extension
_Class_:
Elemental function
_Syntax_:
`RESULT = RSHIFT(I, SHIFT)'
_Arguments_:
I The type shall be `INTEGER'.
SHIFT The type shall be `INTEGER'.
_Return value_:
The return value is of type `INTEGER' and of the same kind as I.
_See also_:
*Note ISHFT::, *Note ISHFTC::, *Note LSHIFT::

File: gfortran.info, Node: SCALE, Next: SCAN, Prev: RSHIFT, Up: Intrinsic Procedures
8.185 `SCALE' -- Scale a real value
===================================
_Description_:
`SCALE(X,I)' returns `X * RADIX(X)**I'.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SCALE(X, I)'
_Arguments_:
X The type of the argument shall be a `REAL'.
I The type of the argument shall be a `INTEGER'.
_Return value_:
The return value is of the same type and kind as X. Its value is
`X * RADIX(X)**I'.
_Example_:
program test_scale
real :: x = 178.1387e-4
integer :: i = 5
print *, scale(x,i), x*radix(x)**i
end program test_scale

File: gfortran.info, Node: SCAN, Next: SECNDS, Prev: SCALE, Up: Intrinsic Procedures
8.186 `SCAN' -- Scan a string for the presence of a set of characters
=====================================================================
_Description_:
Scans a STRING for any of the characters in a SET of characters.
If BACK is either absent or equals `FALSE', this function returns
the position of the leftmost character of STRING that is in SET.
If BACK equals `TRUE', the rightmost position is returned. If no
character of SET is found in STRING, the result is zero.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SCAN(STRING, SET[, BACK [, KIND]])'
_Arguments_:
STRING Shall be of type `CHARACTER'.
SET Shall be of type `CHARACTER'.
BACK (Optional) shall be of type `LOGICAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_Example_:
PROGRAM test_scan
WRITE(*,*) SCAN("FORTRAN", "AO") ! 2, found 'O'
WRITE(*,*) SCAN("FORTRAN", "AO", .TRUE.) ! 6, found 'A'
WRITE(*,*) SCAN("FORTRAN", "C++") ! 0, found none
END PROGRAM
_See also_:
*Note INDEX intrinsic::, *Note VERIFY::

File: gfortran.info, Node: SECNDS, Next: SECOND, Prev: SCAN, Up: Intrinsic Procedures
8.187 `SECNDS' -- Time function
===============================
_Description_:
`SECNDS(X)' gets the time in seconds from the real-time system
clock. X is a reference time, also in seconds. If this is zero,
the time in seconds from midnight is returned. This function is
non-standard and its use is discouraged.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = SECNDS (X)'
_Arguments_:
T Shall be of type `REAL(4)'.
X Shall be of type `REAL(4)'.
_Return value_:
None
_Example_:
program test_secnds
integer :: i
real(4) :: t1, t2
print *, secnds (0.0) ! seconds since midnight
t1 = secnds (0.0) ! reference time
do i = 1, 10000000 ! do something
end do
t2 = secnds (t1) ! elapsed time
print *, "Something took ", t2, " seconds."
end program test_secnds

File: gfortran.info, Node: SECOND, Next: SELECTED_CHAR_KIND, Prev: SECNDS, Up: Intrinsic Procedures
8.188 `SECOND' -- CPU time function
===================================
_Description_:
Returns a `REAL(4)' value representing the elapsed CPU time in
seconds. This provides the same functionality as the standard
`CPU_TIME' intrinsic, and is only included for backwards
compatibility.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL SECOND(TIME)'
`TIME = SECOND()'
_Arguments_:
TIME Shall be of type `REAL(4)'.
_Return value_:
In either syntax, TIME is set to the process's current runtime in
seconds.
_See also_:
*Note CPU_TIME::

File: gfortran.info, Node: SELECTED_CHAR_KIND, Next: SELECTED_INT_KIND, Prev: SECOND, Up: Intrinsic Procedures
8.189 `SELECTED_CHAR_KIND' -- Choose character kind
===================================================
_Description_:
`SELECTED_CHAR_KIND(NAME)' returns the kind value for the character
set named NAME, if a character set with such a name is supported,
or -1 otherwise. Currently, supported character sets include
"ASCII" and "DEFAULT", which are equivalent.
_Standard_:
Fortran 2003 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = SELECTED_CHAR_KIND(NAME)'
_Arguments_:
NAME Shall be a scalar and of the default character
type.
_Example_:
program ascii_kind
integer,parameter :: ascii = selected_char_kind("ascii")
character(kind=ascii, len=26) :: s
s = ascii_"abcdefghijklmnopqrstuvwxyz"
print *, s
end program ascii_kind

File: gfortran.info, Node: SELECTED_INT_KIND, Next: SELECTED_REAL_KIND, Prev: SELECTED_CHAR_KIND, Up: Intrinsic Procedures
8.190 `SELECTED_INT_KIND' -- Choose integer kind
================================================
_Description_:
`SELECTED_INT_KIND(R)' return the kind value of the smallest
integer type that can represent all values ranging from -10^R
(exclusive) to 10^R (exclusive). If there is no integer kind that
accommodates this range, `SELECTED_INT_KIND' returns -1.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = SELECTED_INT_KIND(R)'
_Arguments_:
R Shall be a scalar and of type `INTEGER'.
_Example_:
program large_integers
integer,parameter :: k5 = selected_int_kind(5)
integer,parameter :: k15 = selected_int_kind(15)
integer(kind=k5) :: i5
integer(kind=k15) :: i15
print *, huge(i5), huge(i15)
! The following inequalities are always true
print *, huge(i5) >= 10_k5**5-1
print *, huge(i15) >= 10_k15**15-1
end program large_integers

File: gfortran.info, Node: SELECTED_REAL_KIND, Next: SET_EXPONENT, Prev: SELECTED_INT_KIND, Up: Intrinsic Procedures
8.191 `SELECTED_REAL_KIND' -- Choose real kind
==============================================
_Description_:
`SELECTED_REAL_KIND(P,R)' returns the kind value of a real data
type with decimal precision of at least `P' digits and exponent
range greater at least `R'.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = SELECTED_REAL_KIND([P, R])'
_Arguments_:
P (Optional) shall be a scalar and of type
`INTEGER'.
R (Optional) shall be a scalar and of type
`INTEGER'.
At least one argument shall be present.
_Return value_:
`SELECTED_REAL_KIND' returns the value of the kind type parameter
of a real data type with decimal precision of at least `P' digits
and a decimal exponent range of at least `R'. If more than one
real data type meet the criteria, the kind of the data type with
the smallest decimal precision is returned. If no real data type
matches the criteria, the result is
-1 if the processor does not support a real data type with a
precision greater than or equal to `P'
-2 if the processor does not support a real type with an exponent
range greater than or equal to `R'
-3 if neither is supported.
_Example_:
program real_kinds
integer,parameter :: p6 = selected_real_kind(6)
integer,parameter :: p10r100 = selected_real_kind(10,100)
integer,parameter :: r400 = selected_real_kind(r=400)
real(kind=p6) :: x
real(kind=p10r100) :: y
real(kind=r400) :: z
print *, precision(x), range(x)
print *, precision(y), range(y)
print *, precision(z), range(z)
end program real_kinds

File: gfortran.info, Node: SET_EXPONENT, Next: SHAPE, Prev: SELECTED_REAL_KIND, Up: Intrinsic Procedures
8.192 `SET_EXPONENT' -- Set the exponent of the model
=====================================================
_Description_:
`SET_EXPONENT(X, I)' returns the real number whose fractional part
is that that of X and whose exponent part is I.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SET_EXPONENT(X, I)'
_Arguments_:
X Shall be of type `REAL'.
I Shall be of type `INTEGER'.
_Return value_:
The return value is of the same type and kind as X. The real
number whose fractional part is that that of X and whose exponent
part if I is returned; it is `FRACTION(X) * RADIX(X)**I'.
_Example_:
PROGRAM test_setexp
REAL :: x = 178.1387e-4
INTEGER :: i = 17
PRINT *, SET_EXPONENT(x, i), FRACTION(x) * RADIX(x)**i
END PROGRAM

File: gfortran.info, Node: SHAPE, Next: SIGN, Prev: SET_EXPONENT, Up: Intrinsic Procedures
8.193 `SHAPE' -- Determine the shape of an array
================================================
_Description_:
Determines the shape of an array.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = SHAPE(SOURCE)'
_Arguments_:
SOURCE Shall be an array or scalar of any type. If
SOURCE is a pointer it must be associated and
allocatable arrays must be allocated.
_Return value_:
An `INTEGER' array of rank one with as many elements as SOURCE has
dimensions. The elements of the resulting array correspond to the
extend of SOURCE along the respective dimensions. If SOURCE is a
scalar, the result is the rank one array of size zero.
_Example_:
PROGRAM test_shape
INTEGER, DIMENSION(-1:1, -1:2) :: A
WRITE(*,*) SHAPE(A) ! (/ 3, 4 /)
WRITE(*,*) SIZE(SHAPE(42)) ! (/ /)
END PROGRAM
_See also_:
*Note RESHAPE::, *Note SIZE::

File: gfortran.info, Node: SIGN, Next: SIGNAL, Prev: SHAPE, Up: Intrinsic Procedures
8.194 `SIGN' -- Sign copying function
=====================================
_Description_:
`SIGN(A,B)' returns the value of A with the sign of B.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SIGN(A, B)'
_Arguments_:
A Shall be of type `INTEGER' or `REAL'
B Shall be of the same type and kind as A
_Return value_:
The kind of the return value is that of A and B. If B\ge 0 then
the result is `ABS(A)', else it is `-ABS(A)'.
_Example_:
program test_sign
print *, sign(-12,1)
print *, sign(-12,0)
print *, sign(-12,-1)
print *, sign(-12.,1.)
print *, sign(-12.,0.)
print *, sign(-12.,-1.)
end program test_sign
_Specific names_:
Name Arguments Return type Standard
`ISIGN(A,P)' `INTEGER(4)' `INTEGER(4)' f95, gnu
`DSIGN(A,P)' `REAL(8)' `REAL(8)' f95, gnu

File: gfortran.info, Node: SIGNAL, Next: SIN, Prev: SIGN, Up: Intrinsic Procedures
8.195 `SIGNAL' -- Signal handling subroutine (or function)
==========================================================
_Description_:
`SIGNAL(NUMBER, HANDLER [, STATUS])' causes external subroutine
HANDLER to be executed with a single integer argument when signal
NUMBER occurs. If HANDLER is an integer, it can be used to turn
off handling of signal NUMBER or revert to its default action.
See `signal(2)'.
If `SIGNAL' is called as a subroutine and the STATUS argument is
supplied, it is set to the value returned by `signal(2)'.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL SIGNAL(NUMBER, HANDLER [, STATUS])'
`STATUS = SIGNAL(NUMBER, HANDLER)'
_Arguments_:
NUMBER Shall be a scalar integer, with `INTENT(IN)'
HANDLER Signal handler (`INTEGER FUNCTION' or
`SUBROUTINE') or dummy/global `INTEGER' scalar.
`INTEGER'. It is `INTENT(IN)'.
STATUS (Optional) STATUS shall be a scalar integer.
It has `INTENT(OUT)'.
_Return value_:
The `SIGNAL' function returns the value returned by `signal(2)'.
_Example_:
program test_signal
intrinsic signal
external handler_print
call signal (12, handler_print)
call signal (10, 1)
call sleep (30)
end program test_signal

File: gfortran.info, Node: SIN, Next: SINH, Prev: SIGNAL, Up: Intrinsic Procedures
8.196 `SIN' -- Sine function
============================
_Description_:
`SIN(X)' computes the sine of X.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SIN(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has same type and kind as X.
_Example_:
program test_sin
real :: x = 0.0
x = sin(x)
end program test_sin
_Specific names_:
Name Argument Return type Standard
`DSIN(X)' `REAL(8) X' `REAL(8)' f95, gnu
`CSIN(X)' `COMPLEX(4) `COMPLEX(4)' f95, gnu
X'
`ZSIN(X)' `COMPLEX(8) `COMPLEX(8)' f95, gnu
X'
`CDSIN(X)' `COMPLEX(8) `COMPLEX(8)' f95, gnu
X'
_See also_:
*Note ASIN::

File: gfortran.info, Node: SINH, Next: SIZE, Prev: SIN, Up: Intrinsic Procedures
8.197 `SINH' -- Hyperbolic sine function
========================================
_Description_:
`SINH(X)' computes the hyperbolic sine of X.
_Standard_:
Fortran 95 and later, for a complex argument Fortran 2008 or later
_Class_:
Elemental function
_Syntax_:
`RESULT = SINH(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has same type and kind as X.
_Example_:
program test_sinh
real(8) :: x = - 1.0_8
x = sinh(x)
end program test_sinh
_Specific names_:
Name Argument Return type Standard
`DSINH(X)' `REAL(8) X' `REAL(8)' Fortran 95 and
later
_See also_:
*Note ASINH::

File: gfortran.info, Node: SIZE, Next: SIZEOF, Prev: SINH, Up: Intrinsic Procedures
8.198 `SIZE' -- Determine the size of an array
==============================================
_Description_:
Determine the extent of ARRAY along a specified dimension DIM, or
the total number of elements in ARRAY if DIM is absent.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = SIZE(ARRAY[, DIM [, KIND]])'
_Arguments_:
ARRAY Shall be an array of any type. If ARRAY is a
pointer it must be associated and allocatable
arrays must be allocated.
DIM (Optional) shall be a scalar of type `INTEGER'
and its value shall be in the range from 1 to
n, where n equals the rank of ARRAY.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_Example_:
PROGRAM test_size
WRITE(*,*) SIZE((/ 1, 2 /)) ! 2
END PROGRAM
_See also_:
*Note SHAPE::, *Note RESHAPE::

File: gfortran.info, Node: SIZEOF, Next: SLEEP, Prev: SIZE, Up: Intrinsic Procedures
8.199 `SIZEOF' -- Size in bytes of an expression
================================================
_Description_:
`SIZEOF(X)' calculates the number of bytes of storage the
expression `X' occupies.
_Standard_:
GNU extension
_Class_:
Intrinsic function
_Syntax_:
`N = SIZEOF(X)'
_Arguments_:
X The argument shall be of any type, rank or
shape.
_Return value_:
The return value is of type integer and of the system-dependent
kind C_SIZE_T (from the ISO_C_BINDING module). Its value is the
number of bytes occupied by the argument. If the argument has the
`POINTER' attribute, the number of bytes of the storage area
pointed to is returned. If the argument is of a derived type with
`POINTER' or `ALLOCATABLE' components, the return value doesn't
account for the sizes of the data pointed to by these components.
_Example_:
integer :: i
real :: r, s(5)
print *, (sizeof(s)/sizeof(r) == 5)
end
The example will print `.TRUE.' unless you are using a platform
where default `REAL' variables are unusually padded.
_See also_:
*Note C_SIZEOF::

File: gfortran.info, Node: SLEEP, Next: SNGL, Prev: SIZEOF, Up: Intrinsic Procedures
8.200 `SLEEP' -- Sleep for the specified number of seconds
==========================================================
_Description_:
Calling this subroutine causes the process to pause for SECONDS
seconds.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL SLEEP(SECONDS)'
_Arguments_:
SECONDS The type shall be of default `INTEGER'.
_Example_:
program test_sleep
call sleep(5)
end

File: gfortran.info, Node: SNGL, Next: SPACING, Prev: SLEEP, Up: Intrinsic Procedures
8.201 `SNGL' -- Convert double precision real to default real
=============================================================
_Description_:
`SNGL(A)' converts the double precision real A to a default real
value. This is an archaic form of `REAL' that is specific to one
type for A.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SNGL(A)'
_Arguments_:
A The type shall be a double precision `REAL'.
_Return value_:
The return value is of type default `REAL'.
_See also_:
*Note DBLE::

File: gfortran.info, Node: SPACING, Next: SPREAD, Prev: SNGL, Up: Intrinsic Procedures
8.202 `SPACING' -- Smallest distance between two numbers of a given type
========================================================================
_Description_:
Determines the distance between the argument X and the nearest
adjacent number of the same type.
_Standard_:
Fortran 95 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SPACING(X)'
_Arguments_:
X Shall be of type `REAL'.
_Return value_:
The result is of the same type as the input argument X.
_Example_:
PROGRAM test_spacing
INTEGER, PARAMETER :: SGL = SELECTED_REAL_KIND(p=6, r=37)
INTEGER, PARAMETER :: DBL = SELECTED_REAL_KIND(p=13, r=200)
WRITE(*,*) spacing(1.0_SGL) ! "1.1920929E-07" on i686
WRITE(*,*) spacing(1.0_DBL) ! "2.220446049250313E-016" on i686
END PROGRAM
_See also_:
*Note RRSPACING::

File: gfortran.info, Node: SPREAD, Next: SQRT, Prev: SPACING, Up: Intrinsic Procedures
8.203 `SPREAD' -- Add a dimension to an array
=============================================
_Description_:
Replicates a SOURCE array NCOPIES times along a specified
dimension DIM.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = SPREAD(SOURCE, DIM, NCOPIES)'
_Arguments_:
SOURCE Shall be a scalar or an array of any type and
a rank less than seven.
DIM Shall be a scalar of type `INTEGER' with a
value in the range from 1 to n+1, where n
equals the rank of SOURCE.
NCOPIES Shall be a scalar of type `INTEGER'.
_Return value_:
The result is an array of the same type as SOURCE and has rank n+1
where n equals the rank of SOURCE.
_Example_:
PROGRAM test_spread
INTEGER :: a = 1, b(2) = (/ 1, 2 /)
WRITE(*,*) SPREAD(A, 1, 2) ! "1 1"
WRITE(*,*) SPREAD(B, 1, 2) ! "1 1 2 2"
END PROGRAM
_See also_:
*Note UNPACK::

File: gfortran.info, Node: SQRT, Next: SRAND, Prev: SPREAD, Up: Intrinsic Procedures
8.204 `SQRT' -- Square-root function
====================================
_Description_:
`SQRT(X)' computes the square root of X.
_Standard_:
Fortran 77 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = SQRT(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value is of type `REAL' or `COMPLEX'. The kind type
parameter is the same as X.
_Example_:
program test_sqrt
real(8) :: x = 2.0_8
complex :: z = (1.0, 2.0)
x = sqrt(x)
z = sqrt(z)
end program test_sqrt
_Specific names_:
Name Argument Return type Standard
`DSQRT(X)' `REAL(8) X' `REAL(8)' Fortran 95 and
later
`CSQRT(X)' `COMPLEX(4) `COMPLEX(4)' Fortran 95 and
X' later
`ZSQRT(X)' `COMPLEX(8) `COMPLEX(8)' GNU extension
X'
`CDSQRT(X)' `COMPLEX(8) `COMPLEX(8)' GNU extension
X'

File: gfortran.info, Node: SRAND, Next: STAT, Prev: SQRT, Up: Intrinsic Procedures
8.205 `SRAND' -- Reinitialize the random number generator
=========================================================
_Description_:
`SRAND' reinitializes the pseudo-random number generator called by
`RAND' and `IRAND'. The new seed used by the generator is
specified by the required argument SEED.
_Standard_:
GNU extension
_Class_:
Subroutine
_Syntax_:
`CALL SRAND(SEED)'
_Arguments_:
SEED Shall be a scalar `INTEGER(kind=4)'.
_Return value_:
Does not return anything.
_Example_:
See `RAND' and `IRAND' for examples.
_Notes_:
The Fortran 2003 standard specifies the intrinsic `RANDOM_SEED' to
initialize the pseudo-random numbers generator and `RANDOM_NUMBER'
to generate pseudo-random numbers. Please note that in GNU
Fortran, these two sets of intrinsics (`RAND', `IRAND' and `SRAND'
on the one hand, `RANDOM_NUMBER' and `RANDOM_SEED' on the other
hand) access two independent pseudo-random number generators.
_See also_:
*Note RAND::, *Note RANDOM_SEED::, *Note RANDOM_NUMBER::

File: gfortran.info, Node: STAT, Next: SUM, Prev: SRAND, Up: Intrinsic Procedures
8.206 `STAT' -- Get file status
===============================
_Description_:
This function returns information about a file. No permissions are
required on the file itself, but execute (search) permission is
required on all of the directories in path that lead to the file.
The elements that are obtained and stored in the array `VALUES':
`VALUES(1)'Device ID
`VALUES(2)'Inode number
`VALUES(3)'File mode
`VALUES(4)'Number of links
`VALUES(5)'Owner's uid
`VALUES(6)'Owner's gid
`VALUES(7)'ID of device containing directory entry for
file (0 if not available)
`VALUES(8)'File size (bytes)
`VALUES(9)'Last access time
`VALUES(10)'Last modification time
`VALUES(11)'Last file status change time
`VALUES(12)'Preferred I/O block size (-1 if not available)
`VALUES(13)'Number of blocks allocated (-1 if not
available)
Not all these elements are relevant on all systems. If an element
is not relevant, it is returned as 0.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL STAT(NAME, VALUES [, STATUS])'
_Arguments_:
NAME The type shall be `CHARACTER', of the default
kind and a valid path within the file system.
VALUES The type shall be `INTEGER(4), DIMENSION(13)'.
STATUS (Optional) status flag of type `INTEGER(4)'.
Returns 0 on success and a system specific
error code otherwise.
_Example_:
PROGRAM test_stat
INTEGER, DIMENSION(13) :: buff
INTEGER :: status
CALL STAT("/etc/passwd", buff, status)
IF (status == 0) THEN
WRITE (*, FMT="('Device ID:', T30, I19)") buff(1)
WRITE (*, FMT="('Inode number:', T30, I19)") buff(2)
WRITE (*, FMT="('File mode (octal):', T30, O19)") buff(3)
WRITE (*, FMT="('Number of links:', T30, I19)") buff(4)
WRITE (*, FMT="('Owner''s uid:', T30, I19)") buff(5)
WRITE (*, FMT="('Owner''s gid:', T30, I19)") buff(6)
WRITE (*, FMT="('Device where located:', T30, I19)") buff(7)
WRITE (*, FMT="('File size:', T30, I19)") buff(8)
WRITE (*, FMT="('Last access time:', T30, A19)") CTIME(buff(9))
WRITE (*, FMT="('Last modification time', T30, A19)") CTIME(buff(10))
WRITE (*, FMT="('Last status change time:', T30, A19)") CTIME(buff(11))
WRITE (*, FMT="('Preferred block size:', T30, I19)") buff(12)
WRITE (*, FMT="('No. of blocks allocated:', T30, I19)") buff(13)
END IF
END PROGRAM
_See also_:
To stat an open file: *Note FSTAT::, to stat a link: *Note LSTAT::

File: gfortran.info, Node: SUM, Next: SYMLNK, Prev: STAT, Up: Intrinsic Procedures
8.207 `SUM' -- Sum of array elements
====================================
_Description_:
Adds the elements of ARRAY along dimension DIM if the
corresponding element in MASK is `TRUE'.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = SUM(ARRAY[, MASK])'
`RESULT = SUM(ARRAY, DIM[, MASK])'
_Arguments_:
ARRAY Shall be an array of type `INTEGER', `REAL' or
`COMPLEX'.
DIM (Optional) shall be a scalar of type `INTEGER'
with a value in the range from 1 to n, where n
equals the rank of ARRAY.
MASK (Optional) shall be of type `LOGICAL' and
either be a scalar or an array of the same
shape as ARRAY.
_Return value_:
The result is of the same type as ARRAY.
If DIM is absent, a scalar with the sum of all elements in ARRAY
is returned. Otherwise, an array of rank n-1, where n equals the
rank of ARRAY,and a shape similar to that of ARRAY with dimension
DIM dropped is returned.
_Example_:
PROGRAM test_sum
INTEGER :: x(5) = (/ 1, 2, 3, 4 ,5 /)
print *, SUM(x) ! all elements, sum = 15
print *, SUM(x, MASK=MOD(x, 2)==1) ! odd elements, sum = 9
END PROGRAM
_See also_:
*Note PRODUCT::

File: gfortran.info, Node: SYMLNK, Next: SYSTEM, Prev: SUM, Up: Intrinsic Procedures
8.208 `SYMLNK' -- Create a symbolic link
========================================
_Description_:
Makes a symbolic link from file PATH1 to PATH2. A null character
(`CHAR(0)') can be used to mark the end of the names in PATH1 and
PATH2; otherwise, trailing blanks in the file names are ignored.
If the STATUS argument is supplied, it contains 0 on success or a
nonzero error code upon return; see `symlink(2)'. If the system
does not supply `symlink(2)', `ENOSYS' is returned.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL SYMLNK(PATH1, PATH2 [, STATUS])'
`STATUS = SYMLNK(PATH1, PATH2)'
_Arguments_:
PATH1 Shall be of default `CHARACTER' type.
PATH2 Shall be of default `CHARACTER' type.
STATUS (Optional) Shall be of default `INTEGER' type.
_See also_:
*Note LINK::, *Note UNLINK::

File: gfortran.info, Node: SYSTEM, Next: SYSTEM_CLOCK, Prev: SYMLNK, Up: Intrinsic Procedures
8.209 `SYSTEM' -- Execute a shell command
=========================================
_Description_:
Passes the command COMMAND to a shell (see `system(3)'). If
argument STATUS is present, it contains the value returned by
`system(3)', which is presumably 0 if the shell command succeeded.
Note that which shell is used to invoke the command is
system-dependent and environment-dependent.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL SYSTEM(COMMAND [, STATUS])'
`STATUS = SYSTEM(COMMAND)'
_Arguments_:
COMMAND Shall be of default `CHARACTER' type.
STATUS (Optional) Shall be of default `INTEGER' type.
_See also_:

File: gfortran.info, Node: SYSTEM_CLOCK, Next: TAN, Prev: SYSTEM, Up: Intrinsic Procedures
8.210 `SYSTEM_CLOCK' -- Time function
=====================================
_Description_:
Determines the COUNT of milliseconds of wall clock time since the
Epoch (00:00:00 UTC, January 1, 1970) modulo COUNT_MAX, COUNT_RATE
determines the number of clock ticks per second. COUNT_RATE and
COUNT_MAX are constant and specific to `gfortran'.
If there is no clock, COUNT is set to `-HUGE(COUNT)', and
COUNT_RATE and COUNT_MAX are set to zero
_Standard_:
Fortran 95 and later
_Class_:
Subroutine
_Syntax_:
`CALL SYSTEM_CLOCK([COUNT, COUNT_RATE, COUNT_MAX])'
_Arguments_:
_Arguments_:
COUNT (Optional) shall be a scalar of type default
`INTEGER' with `INTENT(OUT)'.
COUNT_RATE (Optional) shall be a scalar of type default
`INTEGER' with `INTENT(OUT)'.
COUNT_MAX (Optional) shall be a scalar of type default
`INTEGER' with `INTENT(OUT)'.
_Example_:
PROGRAM test_system_clock
INTEGER :: count, count_rate, count_max
CALL SYSTEM_CLOCK(count, count_rate, count_max)
WRITE(*,*) count, count_rate, count_max
END PROGRAM
_See also_:
*Note DATE_AND_TIME::, *Note CPU_TIME::

File: gfortran.info, Node: TAN, Next: TANH, Prev: SYSTEM_CLOCK, Up: Intrinsic Procedures
8.211 `TAN' -- Tangent function
===============================
_Description_:
`TAN(X)' computes the tangent of X.
_Standard_:
Fortran 77 and later, for a complex argument Fortran 2008 or later
_Class_:
Elemental function
_Syntax_:
`RESULT = TAN(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has same type and kind as X.
_Example_:
program test_tan
real(8) :: x = 0.165_8
x = tan(x)
end program test_tan
_Specific names_:
Name Argument Return type Standard
`DTAN(X)' `REAL(8) X' `REAL(8)' Fortran 95 and
later
_See also_:
*Note ATAN::

File: gfortran.info, Node: TANH, Next: TIME, Prev: TAN, Up: Intrinsic Procedures
8.212 `TANH' -- Hyperbolic tangent function
===========================================
_Description_:
`TANH(X)' computes the hyperbolic tangent of X.
_Standard_:
Fortran 77 and later, for a complex argument Fortran 2008 or later
_Class_:
Elemental function
_Syntax_:
`X = TANH(X)'
_Arguments_:
X The type shall be `REAL' or `COMPLEX'.
_Return value_:
The return value has same type and kind as X. If X is complex, the
imaginary part of the result is in radians. If X is `REAL', the
return value lies in the range - 1 \leq tanh(x) \leq 1 .
_Example_:
program test_tanh
real(8) :: x = 2.1_8
x = tanh(x)
end program test_tanh
_Specific names_:
Name Argument Return type Standard
`DTANH(X)' `REAL(8) X' `REAL(8)' Fortran 95 and
later
_See also_:
*Note ATANH::

File: gfortran.info, Node: TIME, Next: TIME8, Prev: TANH, Up: Intrinsic Procedures
8.213 `TIME' -- Time function
=============================
_Description_:
Returns the current time encoded as an integer (in the manner of
the UNIX function `time(3)'). This value is suitable for passing to
`CTIME()', `GMTIME()', and `LTIME()'.
This intrinsic is not fully portable, such as to systems with
32-bit `INTEGER' types but supporting times wider than 32 bits.
Therefore, the values returned by this intrinsic might be, or
become, negative, or numerically less than previous values, during
a single run of the compiled program.
See *Note TIME8::, for information on a similar intrinsic that
might be portable to more GNU Fortran implementations, though to
fewer Fortran compilers.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = TIME()'
_Return value_:
The return value is a scalar of type `INTEGER(4)'.
_See also_:
*Note CTIME::, *Note GMTIME::, *Note LTIME::, *Note MCLOCK::,
*Note TIME8::

File: gfortran.info, Node: TIME8, Next: TINY, Prev: TIME, Up: Intrinsic Procedures
8.214 `TIME8' -- Time function (64-bit)
=======================================
_Description_:
Returns the current time encoded as an integer (in the manner of
the UNIX function `time(3)'). This value is suitable for passing to
`CTIME()', `GMTIME()', and `LTIME()'.
_Warning:_ this intrinsic does not increase the range of the timing
values over that returned by `time(3)'. On a system with a 32-bit
`time(3)', `TIME8()' will return a 32-bit value, even though it is
converted to a 64-bit `INTEGER(8)' value. That means overflows of
the 32-bit value can still occur. Therefore, the values returned
by this intrinsic might be or become negative or numerically less
than previous values during a single run of the compiled program.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = TIME8()'
_Return value_:
The return value is a scalar of type `INTEGER(8)'.
_See also_:
*Note CTIME::, *Note GMTIME::, *Note LTIME::, *Note MCLOCK8::,
*Note TIME::

File: gfortran.info, Node: TINY, Next: TRAILZ, Prev: TIME8, Up: Intrinsic Procedures
8.215 `TINY' -- Smallest positive number of a real kind
=======================================================
_Description_:
`TINY(X)' returns the smallest positive (non zero) number in the
model of the type of `X'.
_Standard_:
Fortran 95 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = TINY(X)'
_Arguments_:
X Shall be of type `REAL'.
_Return value_:
The return value is of the same type and kind as X
_Example_:
See `HUGE' for an example.

File: gfortran.info, Node: TRAILZ, Next: TRANSFER, Prev: TINY, Up: Intrinsic Procedures
8.216 `TRAILZ' -- Number of trailing zero bits of an integer
============================================================
_Description_:
`TRAILZ' returns the number of trailing zero bits of an integer.
_Standard_:
Fortran 2008 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = TRAILZ(I)'
_Arguments_:
I Shall be of type `INTEGER'.
_Return value_:
The type of the return value is the default `INTEGER'. If all the
bits of `I' are zero, the result value is `BIT_SIZE(I)'.
_Example_:
PROGRAM test_trailz
WRITE (*,*) TRAILZ(8) ! prints 3
END PROGRAM
_See also_:
*Note BIT_SIZE::, *Note LEADZ::

File: gfortran.info, Node: TRANSFER, Next: TRANSPOSE, Prev: TRAILZ, Up: Intrinsic Procedures
8.217 `TRANSFER' -- Transfer bit patterns
=========================================
_Description_:
Interprets the bitwise representation of SOURCE in memory as if it
is the representation of a variable or array of the same type and
type parameters as MOLD.
This is approximately equivalent to the C concept of _casting_ one
type to another.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = TRANSFER(SOURCE, MOLD[, SIZE])'
_Arguments_:
SOURCE Shall be a scalar or an array of any type.
MOLD Shall be a scalar or an array of any type.
SIZE (Optional) shall be a scalar of type `INTEGER'.
_Return value_:
The result has the same type as MOLD, with the bit level
representation of SOURCE. If SIZE is present, the result is a
one-dimensional array of length SIZE. If SIZE is absent but MOLD
is an array (of any size or shape), the result is a one-
dimensional array of the minimum length needed to contain the
entirety of the bitwise representation of SOURCE. If SIZE is
absent and MOLD is a scalar, the result is a scalar.
If the bitwise representation of the result is longer than that of
SOURCE, then the leading bits of the result correspond to those of
SOURCE and any trailing bits are filled arbitrarily.
When the resulting bit representation does not correspond to a
valid representation of a variable of the same type as MOLD, the
results are undefined, and subsequent operations on the result
cannot be guaranteed to produce sensible behavior. For example,
it is possible to create `LOGICAL' variables for which `VAR' and
`.NOT.VAR' both appear to be true.
_Example_:
PROGRAM test_transfer
integer :: x = 2143289344
print *, transfer(x, 1.0) ! prints "NaN" on i686
END PROGRAM

File: gfortran.info, Node: TRANSPOSE, Next: TRIM, Prev: TRANSFER, Up: Intrinsic Procedures
8.218 `TRANSPOSE' -- Transpose an array of rank two
===================================================
_Description_:
Transpose an array of rank two. Element (i, j) of the result has
the value `MATRIX(j, i)', for all i, j.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = TRANSPOSE(MATRIX)'
_Arguments_:
MATRIX Shall be an array of any type and have a rank
of two.
_Return value_:
The result has the same type as MATRIX, and has shape `(/ m, n /)'
if MATRIX has shape `(/ n, m /)'.

File: gfortran.info, Node: TRIM, Next: TTYNAM, Prev: TRANSPOSE, Up: Intrinsic Procedures
8.219 `TRIM' -- Remove trailing blank characters of a string
============================================================
_Description_:
Removes trailing blank characters of a string.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = TRIM(STRING)'
_Arguments_:
STRING Shall be a scalar of type `CHARACTER'.
_Return value_:
A scalar of type `CHARACTER' which length is that of STRING less
the number of trailing blanks.
_Example_:
PROGRAM test_trim
CHARACTER(len=10), PARAMETER :: s = "GFORTRAN "
WRITE(*,*) LEN(s), LEN(TRIM(s)) ! "10 8", with/without trailing blanks
END PROGRAM
_See also_:
*Note ADJUSTL::, *Note ADJUSTR::

File: gfortran.info, Node: TTYNAM, Next: UBOUND, Prev: TRIM, Up: Intrinsic Procedures
8.220 `TTYNAM' -- Get the name of a terminal device.
====================================================
_Description_:
Get the name of a terminal device. For more information, see
`ttyname(3)'.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL TTYNAM(UNIT, NAME)'
`NAME = TTYNAM(UNIT)'
_Arguments_:
UNIT Shall be a scalar `INTEGER'.
NAME Shall be of type `CHARACTER'.
_Example_:
PROGRAM test_ttynam
INTEGER :: unit
DO unit = 1, 10
IF (isatty(unit=unit)) write(*,*) ttynam(unit)
END DO
END PROGRAM
_See also_:
*Note ISATTY::

File: gfortran.info, Node: UBOUND, Next: UMASK, Prev: TTYNAM, Up: Intrinsic Procedures
8.221 `UBOUND' -- Upper dimension bounds of an array
====================================================
_Description_:
Returns the upper bounds of an array, or a single upper bound
along the DIM dimension.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Inquiry function
_Syntax_:
`RESULT = UBOUND(ARRAY [, DIM [, KIND]])'
_Arguments_:
ARRAY Shall be an array, of any type.
DIM (Optional) Shall be a scalar `INTEGER'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind. If DIM is
absent, the result is an array of the upper bounds of ARRAY. If
DIM is present, the result is a scalar corresponding to the upper
bound of the array along that dimension. If ARRAY is an
expression rather than a whole array or array structure component,
or if it has a zero extent along the relevant dimension, the upper
bound is taken to be the number of elements along the relevant
dimension.
_See also_:
*Note LBOUND::

File: gfortran.info, Node: UMASK, Next: UNLINK, Prev: UBOUND, Up: Intrinsic Procedures
8.222 `UMASK' -- Set the file creation mask
===========================================
_Description_:
Sets the file creation mask to MASK. If called as a function, it
returns the old value. If called as a subroutine and argument OLD
if it is supplied, it is set to the old value. See `umask(2)'.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL UMASK(MASK [, OLD])' `OLD = UMASK(MASK)'
_Arguments_:
MASK Shall be a scalar of type `INTEGER'.
OLD (Optional) Shall be a scalar of type `INTEGER'.

File: gfortran.info, Node: UNLINK, Next: UNPACK, Prev: UMASK, Up: Intrinsic Procedures
8.223 `UNLINK' -- Remove a file from the file system
====================================================
_Description_:
Unlinks the file PATH. A null character (`CHAR(0)') can be used to
mark the end of the name in PATH; otherwise, trailing blanks in
the file name are ignored. If the STATUS argument is supplied, it
contains 0 on success or a nonzero error code upon return; see
`unlink(2)'.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
_Standard_:
GNU extension
_Class_:
Subroutine, function
_Syntax_:
`CALL UNLINK(PATH [, STATUS])'
`STATUS = UNLINK(PATH)'
_Arguments_:
PATH Shall be of default `CHARACTER' type.
STATUS (Optional) Shall be of default `INTEGER' type.
_See also_:
*Note LINK::, *Note SYMLNK::

File: gfortran.info, Node: UNPACK, Next: VERIFY, Prev: UNLINK, Up: Intrinsic Procedures
8.224 `UNPACK' -- Unpack an array of rank one into an array
===========================================================
_Description_:
Store the elements of VECTOR in an array of higher rank.
_Standard_:
Fortran 95 and later
_Class_:
Transformational function
_Syntax_:
`RESULT = UNPACK(VECTOR, MASK, FIELD)'
_Arguments_:
VECTOR Shall be an array of any type and rank one. It
shall have at least as many elements as MASK
has `TRUE' values.
MASK Shall be an array of type `LOGICAL'.
FIELD Shall be of the same type as VECTOR and have
the same shape as MASK.
_Return value_:
The resulting array corresponds to FIELD with `TRUE' elements of
MASK replaced by values from VECTOR in array element order.
_Example_:
PROGRAM test_unpack
integer :: vector(2) = (/1,1/)
logical :: mask(4) = (/ .TRUE., .FALSE., .FALSE., .TRUE. /)
integer :: field(2,2) = 0, unity(2,2)
! result: unity matrix
unity = unpack(vector, reshape(mask, (/2,2/)), field)
END PROGRAM
_See also_:
*Note PACK::, *Note SPREAD::

File: gfortran.info, Node: VERIFY, Next: XOR, Prev: UNPACK, Up: Intrinsic Procedures
8.225 `VERIFY' -- Scan a string for the absence of a set of characters
======================================================================
_Description_:
Verifies that all the characters in a SET are present in a STRING.
If BACK is either absent or equals `FALSE', this function returns
the position of the leftmost character of STRING that is not in
SET. If BACK equals `TRUE', the rightmost position is returned. If
all characters of SET are found in STRING, the result is zero.
_Standard_:
Fortran 95 and later, with KIND argument Fortran 2003 and later
_Class_:
Elemental function
_Syntax_:
`RESULT = VERIFY(STRING, SET[, BACK [, KIND]])'
_Arguments_:
STRING Shall be of type `CHARACTER'.
SET Shall be of type `CHARACTER'.
BACK (Optional) shall be of type `LOGICAL'.
KIND (Optional) An `INTEGER' initialization
expression indicating the kind parameter of
the result.
_Return value_:
The return value is of type `INTEGER' and of kind KIND. If KIND is
absent, the return value is of default integer kind.
_Example_:
PROGRAM test_verify
WRITE(*,*) VERIFY("FORTRAN", "AO") ! 1, found 'F'
WRITE(*,*) VERIFY("FORTRAN", "FOO") ! 3, found 'R'
WRITE(*,*) VERIFY("FORTRAN", "C++") ! 1, found 'F'
WRITE(*,*) VERIFY("FORTRAN", "C++", .TRUE.) ! 7, found 'N'
WRITE(*,*) VERIFY("FORTRAN", "FORTRAN") ! 0' found none
END PROGRAM
_See also_:
*Note SCAN::, *Note INDEX intrinsic::

File: gfortran.info, Node: XOR, Prev: VERIFY, Up: Intrinsic Procedures
8.226 `XOR' -- Bitwise logical exclusive OR
===========================================
_Description_:
Bitwise logical exclusive or.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. For integer arguments, programmers should consider
the use of the *Note IEOR:: intrinsic and for logical arguments the
`.NEQV.' operator, which are both defined by the Fortran standard.
_Standard_:
GNU extension
_Class_:
Function
_Syntax_:
`RESULT = XOR(I, J)'
_Arguments_:
I The type shall be either a scalar `INTEGER'
type or a scalar `LOGICAL' type.
J The type shall be the same as the type of I.
_Return value_:
The return type is either a scalar `INTEGER' or a scalar
`LOGICAL'. If the kind type parameters differ, then the smaller
kind type is implicitly converted to larger kind, and the return
has the larger kind.
_Example_:
PROGRAM test_xor
LOGICAL :: T = .TRUE., F = .FALSE.
INTEGER :: a, b
DATA a / Z'F' /, b / Z'3' /
WRITE (*,*) XOR(T, T), XOR(T, F), XOR(F, T), XOR(F, F)
WRITE (*,*) XOR(a, b)
END PROGRAM
_See also_:
Fortran 95 elemental function: *Note IEOR::

File: gfortran.info, Node: Intrinsic Modules, Next: Contributing, Prev: Intrinsic Procedures, Up: Top
9 Intrinsic Modules
*******************
* Menu:
* ISO_FORTRAN_ENV::
* ISO_C_BINDING::
* OpenMP Modules OMP_LIB and OMP_LIB_KINDS::

File: gfortran.info, Node: ISO_FORTRAN_ENV, Next: ISO_C_BINDING, Up: Intrinsic Modules
9.1 `ISO_FORTRAN_ENV'
=====================
_Standard_:
Fortran 2003 and later; `INT8', `INT16', `INT32', `INT64',
`REAL32', `REAL64', `REAL128' are Fortran 2008 or later
The `ISO_FORTRAN_ENV' module provides the following scalar
default-integer named constants:
`CHARACTER_STORAGE_SIZE':
Size in bits of the character storage unit.
`ERROR_UNIT':
Identifies the preconnected unit used for error reporting.
`FILE_STORAGE_SIZE':
Size in bits of the file-storage unit.
`INPUT_UNIT':
Identifies the preconnected unit identified by the asterisk (`*')
in `READ' statement.
`INT8', `INT16', `INT32', `INT64'
Kind type parameters to specify an INTEGER type with a storage
size of 16, 32, and 64 bits. It is negative if a target platform
does not support the particular kind.
`IOSTAT_END':
The value assigned to the variable passed to the IOSTAT= specifier
of an input/output statement if an end-of-file condition occurred.
`IOSTAT_EOR':
The value assigned to the variable passed to the IOSTAT= specifier
of an input/output statement if an end-of-record condition
occurred.
`NUMERIC_STORAGE_SIZE':
The size in bits of the numeric storage unit.
`OUTPUT_UNIT':
Identifies the preconnected unit identified by the asterisk (`*')
in `WRITE' statement.
`REAL32', `REAL64', `REAL128'
Kind type parameters to specify a REAL type with a storage size of
32, 64, and 128 bits. It is negative if a target platform does not
support the particular kind.

File: gfortran.info, Node: ISO_C_BINDING, Next: OpenMP Modules OMP_LIB and OMP_LIB_KINDS, Prev: ISO_FORTRAN_ENV, Up: Intrinsic Modules
9.2 `ISO_C_BINDING'
===================
_Standard_:
Fortran 2003 and later, GNU extensions
The following intrinsic procedures are provided by the module; their
definition can be found in the section Intrinsic Procedures of this
manual.
`C_ASSOCIATED'
`C_F_POINTER'
`C_F_PROCPOINTER'
`C_FUNLOC'
`C_LOC'
The `ISO_C_BINDING' module provides the following named constants of
type default integer, which can be used as KIND type parameters.
In addition to the integer named constants required by the Fortran
2003 standard, GNU Fortran provides as an extension named constants for
the 128-bit integer types supported by the C compiler: `C_INT128_T,
C_INT_LEAST128_T, C_INT_FAST128_T'.
Fortran Named constant C type Extension
Type
`INTEGER' `C_INT' `int'
`INTEGER' `C_SHORT' `short int'
`INTEGER' `C_LONG' `long int'
`INTEGER' `C_LONG_LONG' `long long int'
`INTEGER' `C_SIGNED_CHAR' `signed char'/`unsigned
char'
`INTEGER' `C_SIZE_T' `size_t'
`INTEGER' `C_INT8_T' `int8_t'
`INTEGER' `C_INT16_T' `int16_t'
`INTEGER' `C_INT32_T' `int32_t'
`INTEGER' `C_INT64_T' `int64_t'
`INTEGER' `C_INT128_T' `int128_t' Ext.
`INTEGER' `C_INT_LEAST8_T' `int_least8_t'
`INTEGER' `C_INT_LEAST16_T' `int_least16_t'
`INTEGER' `C_INT_LEAST32_T' `int_least32_t'
`INTEGER' `C_INT_LEAST64_T' `int_least64_t'
`INTEGER' `C_INT_LEAST128_T' `int_least128_t' Ext.
`INTEGER' `C_INT_FAST8_T' `int_fast8_t'
`INTEGER' `C_INT_FAST16_T' `int_fast16_t'
`INTEGER' `C_INT_FAST32_T' `int_fast32_t'
`INTEGER' `C_INT_FAST64_T' `int_fast64_t'
`INTEGER' `C_INT_FAST128_T' `int_fast128_t' Ext.
`INTEGER' `C_INTMAX_T' `intmax_t'
`INTEGER' `C_INTPTR_T' `intptr_t'
`REAL' `C_FLOAT' `float'
`REAL' `C_DOUBLE' `double'
`REAL' `C_LONG_DOUBLE' `long double'
`COMPLEX' `C_FLOAT_COMPLEX' `float _Complex'
`COMPLEX' `C_DOUBLE_COMPLEX' `double _Complex'
`COMPLEX' `C_LONG_DOUBLE_COMPLEX' `long double _Complex'
`LOGICAL' `C_BOOL' `_Bool'
`CHARACTER' `C_CHAR' `char'
Additionally, the following parameters of type
`CHARACTER(KIND=C_CHAR)' are defined.
Name C definition Value
`C_NULL_CHAR' null character `'\0''
`C_ALERT' alert `'\a''
`C_BACKSPACE' backspace `'\b''
`C_FORM_FEED' form feed `'\f''
`C_NEW_LINE' new line `'\n''
`C_CARRIAGE_RETURN'carriage return `'\r''
`C_HORIZONTAL_TAB'horizontal tab `'\t''
`C_VERTICAL_TAB'vertical tab `'\v''

File: gfortran.info, Node: OpenMP Modules OMP_LIB and OMP_LIB_KINDS, Prev: ISO_C_BINDING, Up: Intrinsic Modules
9.3 OpenMP Modules `OMP_LIB' and `OMP_LIB_KINDS'
================================================
_Standard_:
OpenMP Application Program Interface v3.0
The OpenMP Fortran runtime library routines are provided both in a
form of two Fortran 90 modules, named `OMP_LIB' and `OMP_LIB_KINDS',
and in a form of a Fortran `include' file named `omp_lib.h'. The
procedures provided by `OMP_LIB' can be found in the *Note
Introduction: (libgomp)Top. manual, the named constants defined in the
`OMP_LIB_KINDS' module are listed below.
For details refer to the actual OpenMP Application Program Interface
v3.0 (http://www.openmp.org/mp-documents/spec30.pdf).
`OMP_LIB_KINDS' provides the following scalar default-integer named
constants:
`omp_integer_kind'
`omp_logical_kind'
`omp_lock_kind'
`omp_nest_lock_kind'
`omp_sched_kind'

File: gfortran.info, Node: Contributing, Next: Copying, Prev: Intrinsic Modules, Up: Top
Contributing
************
Free software is only possible if people contribute to efforts to
create it. We're always in need of more people helping out with ideas
and comments, writing documentation and contributing code.
If you want to contribute to GNU Fortran, have a look at the long
lists of projects you can take on. Some of these projects are small,
some of them are large; some are completely orthogonal to the rest of
what is happening on GNU Fortran, but others are "mainstream" projects
in need of enthusiastic hackers. All of these projects are important!
We'll eventually get around to the things here, but they are also
things doable by someone who is willing and able.
* Menu:
* Contributors::
* Projects::
* Proposed Extensions::

File: gfortran.info, Node: Contributors, Next: Projects, Up: Contributing
Contributors to GNU Fortran
===========================
Most of the parser was hand-crafted by _Andy Vaught_, who is also the
initiator of the whole project. Thanks Andy! Most of the interface
with GCC was written by _Paul Brook_.
The following individuals have contributed code and/or ideas and
significant help to the GNU Fortran project (in alphabetical order):
- Janne Blomqvist
- Steven Bosscher
- Paul Brook
- Tobias Burnus
- Franc,ois-Xavier Coudert
- Bud Davis
- Jerry DeLisle
- Erik Edelmann
- Bernhard Fischer
- Daniel Franke
- Richard Guenther
- Richard Henderson
- Katherine Holcomb
- Jakub Jelinek
- Niels Kristian Bech Jensen
- Steven Johnson
- Steven G. Kargl
- Thomas Koenig
- Asher Langton
- H. J. Lu
- Toon Moene
- Brooks Moses
- Andrew Pinski
- Tim Prince
- Christopher D. Rickett
- Richard Sandiford
- Tobias Schlu"ter
- Roger Sayle
- Paul Thomas
- Andy Vaught
- Feng Wang
- Janus Weil
- Daniel Kraft
The following people have contributed bug reports, smaller or larger
patches, and much needed feedback and encouragement for the GNU Fortran
project:
- Bill Clodius
- Dominique d'Humie`res
- Kate Hedstrom
- Erik Schnetter
- Joost VandeVondele
Many other individuals have helped debug, test and improve the GNU
Fortran compiler over the past few years, and we welcome you to do the
same! If you already have done so, and you would like to see your name
listed in the list above, please contact us.

File: gfortran.info, Node: Projects, Next: Proposed Extensions, Prev: Contributors, Up: Contributing
Projects
========
_Help build the test suite_
Solicit more code for donation to the test suite: the more
extensive the testsuite, the smaller the risk of breaking things
in the future! We can keep code private on request.
_Bug hunting/squishing_
Find bugs and write more test cases! Test cases are especially very
welcome, because it allows us to concentrate on fixing bugs
instead of isolating them. Going through the bugzilla database at
`http://gcc.gnu.org/bugzilla/' to reduce testcases posted there and
add more information (for example, for which version does the
testcase work, for which versions does it fail?) is also very
helpful.

File: gfortran.info, Node: Proposed Extensions, Prev: Projects, Up: Contributing
Proposed Extensions
===================
Here's a list of proposed extensions for the GNU Fortran compiler, in
no particular order. Most of these are necessary to be fully
compatible with existing Fortran compilers, but they are not part of
the official J3 Fortran 95 standard.
Compiler extensions:
--------------------
* User-specified alignment rules for structures.
* Automatically extend single precision constants to double.
* Compile code that conserves memory by dynamically allocating
common and module storage either on stack or heap.
* Compile flag to generate code for array conformance checking
(suggest -CC).
* User control of symbol names (underscores, etc).
* Compile setting for maximum size of stack frame size before
spilling parts to static or heap.
* Flag to force local variables into static space.
* Flag to force local variables onto stack.
Environment Options
-------------------
* Pluggable library modules for random numbers, linear algebra. LA
should use BLAS calling conventions.
* Environment variables controlling actions on arithmetic exceptions
like overflow, underflow, precision loss--Generate NaN, abort,
default. action.
* Set precision for fp units that support it (i387).
* Variable for setting fp rounding mode.
* Variable to fill uninitialized variables with a user-defined bit
pattern.
* Environment variable controlling filename that is opened for that
unit number.
* Environment variable to clear/trash memory being freed.
* Environment variable to control tracing of allocations and frees.
* Environment variable to display allocated memory at normal program
end.
* Environment variable for filename for * IO-unit.
* Environment variable for temporary file directory.
* Environment variable forcing standard output to be line buffered
(unix).

File: gfortran.info, Node: Copying, Next: GNU Free Documentation License, Prev: Contributing, Up: Top
GNU General Public License
**************************
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. `http://fsf.org/'
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
Preamble
========
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Termination of your rights under this section does not terminate
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the scope of its coverage, prohibits the exercise of, or is
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Nothing in this License shall be construed as excluding or limiting
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12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order,
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License, they do not excuse you from the conditions of this
License. If you cannot convey a covered work so as to satisfy
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pertinent obligations, then as a consequence you may not convey it
at all. For example, if you agree to terms that obligate you to
collect a royalty for further conveying from those to whom you
convey the Program, the only way you could satisfy both those
terms and this License would be to refrain entirely from conveying
the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a
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of this License will continue to apply to the part which is the
covered work, but the special requirements of the GNU Affero
General Public License, section 13, concerning interaction through
a network will apply to the combination as such.
14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new
versions of the GNU General Public License from time to time.
Such new versions will be similar in spirit to the present
version, but may differ in detail to address new problems or
concerns.
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any version ever published by the Free Software Foundation.
If the Program specifies that a proxy can decide which future
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15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE
COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.
SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
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16. Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES
AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA
BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF
THE POSSIBILITY OF SUCH DAMAGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely
approximates an absolute waiver of all civil liability in
connection with the Program, unless a warranty or assumption of
liability accompanies a copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
===========================
How to Apply These Terms to Your New Programs
=============================================
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least the
"copyright" line and a pointer to where the full notice is found.
ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
Copyright (C) YEAR NAME OF AUTHOR
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see `http://www.gnu.org/licenses/'.
Also add information on how to contact you by electronic and paper
mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
PROGRAM Copyright (C) YEAR NAME OF AUTHOR
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the
appropriate parts of the General Public License. Of course, your
program's commands might be different; for a GUI interface, you would
use an "about box".
You should also get your employer (if you work as a programmer) or
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. For more information on this, and how to apply and follow
the GNU GPL, see `http://www.gnu.org/licenses/'.
The GNU General Public License does not permit incorporating your
program into proprietary programs. If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library. If this is what you want to do, use the
GNU Lesser General Public License instead of this License. But first,
please read `http://www.gnu.org/philosophy/why-not-lgpl.html'.

File: gfortran.info, Node: GNU Free Documentation License, Next: Funding, Prev: Copying, Up: Top
GNU Free Documentation License
******************************
Version 1.2, November 2002
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book.
We recommend this License principally for works whose purpose is
instruction or reference.
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium,
that contains a notice placed by the copyright holder saying it
can be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
"Document", below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you". You
accept the license if you copy, modify or distribute the work in a
way requiring permission under copyright law.
A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
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A "Secondary Section" is a named appendix or a front-matter section
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of legal, commercial, philosophical, ethical or political position
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The "Invariant Sections" are certain Secondary Sections whose
titles are designated, as being those of Invariant Sections, in
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The Document may contain zero Invariant Sections. If the Document
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The "Cover Texts" are certain short passages of text that are
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that says that the Document is released under this License. A
Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy,
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markup, has been arranged to thwart or discourage subsequent
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human modification. Examples of transparent image formats include
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can be read and edited only by proprietary word processors, SGML or
XML for which the DTD and/or processing tools are not generally
available, and the machine-generated HTML, PostScript or PDF
produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the
material this License requires to appear in the title page. For
works in formats which do not have any title page as such, "Title
Page" means the text near the most prominent appearance of the
work's title, preceding the beginning of the body of the text.
A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
"Acknowledgements", "Dedications", "Endorsements", or "History".)
To "Preserve the Title" of such a section when you modify the
Document means that it remains a section "Entitled XYZ" according
to this definition.
The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document. These
Warranty Disclaimers are considered to be included by reference in
this License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and
has no effect on the meaning of this License.
2. VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License
applies to the Document are reproduced in all copies, and that you
add no other conditions whatsoever to those of this License. You
may not use technical measures to obstruct or control the reading
or further copying of the copies you make or distribute. However,
you may accept compensation in exchange for copies. If you
distribute a large enough number of copies you must also follow
the conditions in section 3.
You may also lend copies, under the same conditions stated above,
and you may publicly display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and
the Document's license notice requires Cover Texts, you must
enclose the copies in covers that carry, clearly and legibly, all
these Cover Texts: Front-Cover Texts on the front cover, and
Back-Cover Texts on the back cover. Both covers must also clearly
and legibly identify you as the publisher of these copies. The
front cover must present the full title with all words of the
title equally prominent and visible. You may add other material
on the covers in addition. Copying with changes limited to the
covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in
other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto
adjacent pages.
If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a
machine-readable Transparent copy along with each Opaque copy, or
state in or with each Opaque copy a computer-network location from
which the general network-using public has access to download
using public-standard network protocols a complete Transparent
copy of the Document, free of added material. If you use the
latter option, you must take reasonably prudent steps, when you
begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or
retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of
copies, to give them a chance to provide you with an updated
version of the Document.
4. MODIFICATIONS
You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with
the Modified Version filling the role of the Document, thus
licensing distribution and modification of the Modified Version to
whoever possesses a copy of it. In addition, you must do these
things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title
distinct from that of the Document, and from those of
previous versions (which should, if there were any, be listed
in the History section of the Document). You may use the
same title as a previous version if the original publisher of
that version gives permission.
B. List on the Title Page, as authors, one or more persons or
entities responsible for authorship of the modifications in
the Modified Version, together with at least five of the
principal authors of the Document (all of its principal
authors, if it has fewer than five), unless they release you
from this requirement.
C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license
notice giving the public permission to use the Modified
Version under the terms of this License, in the form shown in
the Addendum below.
G. Preserve in that license notice the full lists of Invariant
Sections and required Cover Texts given in the Document's
license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on
the Title Page. If there is no section Entitled "History" in
the Document, create one stating the title, year, authors,
and publisher of the Document as given on its Title Page,
then add an item describing the Modified Version as stated in
the previous sentence.
J. Preserve the network location, if any, given in the Document
for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for
previous versions it was based on. These may be placed in
the "History" section. You may omit a network location for a
work that was published at least four years before the
Document itself, or if the original publisher of the version
it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, and preserve in the
section all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section
titles.
M. Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant
Section.
O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this,
add their titles to the list of Invariant Sections in the Modified
Version's license notice. These titles must be distinct from any
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You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
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has been approved by an organization as the authoritative
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and a passage of up to 25 words as a Back-Cover Text, to the end
of the list of Cover Texts in the Modified Version. Only one
passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the
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you are acting on behalf of, you may not add another; but you may
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5. COMBINING DOCUMENTS
You may combine the Document with other documents released under
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The combined work need only contain one copy of this License, and
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must delete all sections Entitled "Endorsements."
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rules of this License for verbatim copying of each of the
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distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow
this License in all other respects regarding verbatim copying of
that document.
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Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
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If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
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License. However, parties who have received copies, or rights,
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ADDENDUM: How to use this License for your documents
====================================================
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the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
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If you have Invariant Sections without Cover Texts, or some other
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If your document contains nontrivial examples of program code, we
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File: gfortran.info, Node: Funding, Next: Option Index, Prev: GNU Free Documentation License, Up: Top
Funding Free Software
*********************
If you want to have more free software a few years from now, it makes
sense for you to help encourage people to contribute funds for its
development. The most effective approach known is to encourage
commercial redistributors to donate.
Users of free software systems can boost the pace of development by
encouraging for-a-fee distributors to donate part of their selling price
to free software developers--the Free Software Foundation, and others.
The way to convince distributors to do this is to demand it and
expect it from them. So when you compare distributors, judge them
partly by how much they give to free software development. Show
distributors they must compete to be the one who gives the most.
To make this approach work, you must insist on numbers that you can
compare, such as, "We will donate ten dollars to the Frobnitz project
for each disk sold." Don't be satisfied with a vague promise, such as
"A portion of the profits are donated," since it doesn't give a basis
for comparison.
Even a precise fraction "of the profits from this disk" is not very
meaningful, since creative accounting and unrelated business decisions
can greatly alter what fraction of the sales price counts as profit.
If the price you pay is $50, ten percent of the profit is probably less
than a dollar; it might be a few cents, or nothing at all.
Some redistributors do development work themselves. This is useful
too; but to keep everyone honest, you need to inquire how much they do,
and what kind. Some kinds of development make much more long-term
difference than others. For example, maintaining a separate version of
a program contributes very little; maintaining the standard version of a
program for the whole community contributes much. Easy new ports
contribute little, since someone else would surely do them; difficult
ports such as adding a new CPU to the GNU Compiler Collection
contribute more; major new features or packages contribute the most.
By establishing the idea that supporting further development is "the
proper thing to do" when distributing free software for a fee, we can
assure a steady flow of resources into making more free software.
Copyright (C) 1994 Free Software Foundation, Inc.
Verbatim copying and redistribution of this section is permitted
without royalty; alteration is not permitted.

File: gfortran.info, Node: Option Index, Next: Keyword Index, Prev: Funding, Up: Top
Option Index
************
`gfortran''s command line options are indexed here without any initial
`-' or `--'. Where an option has both positive and negative forms (such
as -foption and -fno-option), relevant entries in the manual are
indexed under the most appropriate form; it may sometimes be useful to
look up both forms.
�[index�]
* Menu:
* A-PREDICATE=ANSWER: Preprocessing Options.
(line 120)
* APREDICATE=ANSWER: Preprocessing Options.
(line 114)
* backslash: Fortran Dialect Options.
(line 62)
* C: Preprocessing Options.
(line 123)
* CC: Preprocessing Options.
(line 138)
* cpp: Preprocessing Options.
(line 13)
* dD: Preprocessing Options.
(line 35)
* dI: Preprocessing Options.
(line 51)
* dM: Preprocessing Options.
(line 26)
* dN: Preprocessing Options.
(line 41)
* DNAME: Preprocessing Options.
(line 153)
* DNAME=DEFINITION: Preprocessing Options.
(line 156)
* dU: Preprocessing Options.
(line 44)
* falign-commons: Code Gen Options. (line 304)
* fall-intrinsics: Fortran Dialect Options.
(line 18)
* fbacktrace: Debugging Options. (line 31)
* fblas-matmul-limit: Code Gen Options. (line 260)
* fbounds-check: Code Gen Options. (line 192)
* fcheck: Code Gen Options. (line 143)
* fcheck-array-temporaries: Code Gen Options. (line 195)
* fconvert=CONVERSION: Runtime Options. (line 9)
* fcray-pointer: Fortran Dialect Options.
(line 108)
* fd-lines-as-code: Fortran Dialect Options.
(line 29)
* fd-lines-as-comments: Fortran Dialect Options.
(line 29)
* fdefault-double-8: Fortran Dialect Options.
(line 36)
* fdefault-integer-8: Fortran Dialect Options.
(line 44)
* fdefault-real-8: Fortran Dialect Options.
(line 49)
* fdollar-ok: Fortran Dialect Options.
(line 56)
* fdump-core: Debugging Options. (line 38)
* fdump-parse-tree: Debugging Options. (line 10)
* fexternal-blas: Code Gen Options. (line 252)
* ff2c: Code Gen Options. (line 25)
* ffixed-line-length-N: Fortran Dialect Options.
(line 79)
* ffpe-trap=LIST: Debugging Options. (line 14)
* ffree-form: Fortran Dialect Options.
(line 12)
* ffree-line-length-N: Fortran Dialect Options.
(line 92)
* fimplicit-none: Fortran Dialect Options.
(line 103)
* finit-character: Code Gen Options. (line 284)
* finit-integer: Code Gen Options. (line 284)
* finit-local-zero: Code Gen Options. (line 284)
* finit-logical: Code Gen Options. (line 284)
* finit-real: Code Gen Options. (line 284)
* fintrinsic-modules-path DIR: Directory Options. (line 36)
* fmax-array-constructor: Code Gen Options. (line 198)
* fmax-errors=N: Error and Warning Options.
(line 27)
* fmax-identifier-length=N: Fortran Dialect Options.
(line 99)
* fmax-stack-var-size: Code Gen Options. (line 216)
* fmax-subrecord-length=LENGTH: Runtime Options. (line 36)
* fmodule-private: Fortran Dialect Options.
(line 74)
* fno-automatic: Code Gen Options. (line 15)
* fno-fixed-form: Fortran Dialect Options.
(line 12)
* fno-protect-parens: Code Gen Options. (line 315)
* fno-range-check: Runtime Options. (line 20)
* fno-underscoring: Code Gen Options. (line 54)
* fopenmp: Fortran Dialect Options.
(line 112)
* fpack-derived: Code Gen Options. (line 230)
* fpp: Preprocessing Options.
(line 13)
* frange-check: Fortran Dialect Options.
(line 120)
* frecord-marker=LENGTH: Runtime Options. (line 28)
* frecursive: Code Gen Options. (line 271)
* frepack-arrays: Code Gen Options. (line 236)
* fsecond-underscore: Code Gen Options. (line 126)
* fshort-enums <1>: Fortran 2003 status. (line 22)
* fshort-enums: Code Gen Options. (line 246)
* fsign-zero: Runtime Options. (line 41)
* fsyntax-only: Error and Warning Options.
(line 33)
* fwhole-file: Code Gen Options. (line 113)
* fworking-directory: Preprocessing Options.
(line 55)
* H: Preprocessing Options.
(line 176)
* IDIR: Directory Options. (line 14)
* idirafter DIR: Preprocessing Options.
(line 70)
* imultilib DIR: Preprocessing Options.
(line 77)
* iprefix PREFIX: Preprocessing Options.
(line 81)
* iquote DIR: Preprocessing Options.
(line 90)
* isysroot DIR: Preprocessing Options.
(line 86)
* isystem DIR: Preprocessing Options.
(line 97)
* JDIR: Directory Options. (line 29)
* MDIR: Directory Options. (line 29)
* nostdinc: Preprocessing Options.
(line 105)
* P: Preprocessing Options.
(line 181)
* pedantic: Error and Warning Options.
(line 38)
* pedantic-errors: Error and Warning Options.
(line 57)
* static-libgfortran: Link Options. (line 11)
* std=STD option: Fortran Dialect Options.
(line 132)
* UNAME: Preprocessing Options.
(line 187)
* undef: Preprocessing Options.
(line 110)
* Waliasing: Error and Warning Options.
(line 68)
* Walign-commons: Error and Warning Options.
(line 171)
* Wall: Error and Warning Options.
(line 61)
* Wampersand: Error and Warning Options.
(line 85)
* Warray-temporaries: Error and Warning Options.
(line 93)
* Wcharacter-truncation: Error and Warning Options.
(line 98)
* Wconversion: Error and Warning Options.
(line 104)
* Werror: Error and Warning Options.
(line 177)
* Wimplicit-interface: Error and Warning Options.
(line 107)
* Wimplicit-procedure: Error and Warning Options.
(line 113)
* Wintrinsic-shadow: Error and Warning Options.
(line 158)
* Wintrinsics-std: Error and Warning Options.
(line 117)
* Wline-truncation: Error and Warning Options.
(line 101)
* Wsurprising: Error and Warning Options.
(line 124)
* Wtabs: Error and Warning Options.
(line 146)
* Wunderflow: Error and Warning Options.
(line 154)
* Wunused-parameter: Error and Warning Options.
(line 164)

File: gfortran.info, Node: Keyword Index, Prev: Option Index, Up: Top
Keyword Index
*************
�[index�]
* Menu:
* $: Fortran Dialect Options.
(line 56)
* %LOC: Argument list functions.
(line 6)
* %REF: Argument list functions.
(line 6)
* %VAL: Argument list functions.
(line 6)
* &: Error and Warning Options.
(line 85)
* [...]: Fortran 2003 status. (line 14)
* _gfortran_set_args: _gfortran_set_args. (line 6)
* _gfortran_set_convert: _gfortran_set_convert.
(line 6)
* _gfortran_set_fpe: _gfortran_set_fpe. (line 6)
* _gfortran_set_max_subrecord_length: _gfortran_set_max_subrecord_length.
(line 6)
* _gfortran_set_options: _gfortran_set_options.
(line 6)
* _gfortran_set_record_marker: _gfortran_set_record_marker.
(line 6)
* ABORT: ABORT. (line 6)
* ABS: ABS. (line 6)
* absolute value: ABS. (line 6)
* ABSTRACT type: Fortran 2003 status. (line 69)
* ACCESS: ACCESS. (line 6)
* ACCESS='STREAM' I/O: Fortran 2003 status. (line 40)
* ACHAR: ACHAR. (line 6)
* ACOS: ACOS. (line 6)
* ACOSH: ACOSH. (line 6)
* adjust string <1>: ADJUSTR. (line 6)
* adjust string: ADJUSTL. (line 6)
* ADJUSTL: ADJUSTL. (line 6)
* ADJUSTR: ADJUSTR. (line 6)
* AIMAG: AIMAG. (line 6)
* AINT: AINT. (line 6)
* ALARM: ALARM. (line 6)
* ALGAMA: LOG_GAMMA. (line 6)
* aliasing: Error and Warning Options.
(line 68)
* alignment of COMMON blocks <1>: Code Gen Options. (line 304)
* alignment of COMMON blocks: Error and Warning Options.
(line 171)
* ALL: ALL. (line 6)
* all warnings: Error and Warning Options.
(line 61)
* ALLOCATABLE components of derived types: Fortran 2003 status.
(line 32)
* ALLOCATABLE dummy arguments: Fortran 2003 status. (line 28)
* ALLOCATABLE function results: Fortran 2003 status. (line 30)
* ALLOCATE: Fortran 2003 status. (line 34)
* ALLOCATED: ALLOCATED. (line 6)
* allocation, moving: MOVE_ALLOC. (line 6)
* allocation, status: ALLOCATED. (line 6)
* ALOG: LOG. (line 6)
* ALOG10: LOG10. (line 6)
* AMAX0: MAX. (line 6)
* AMAX1: MAX. (line 6)
* AMIN0: MIN. (line 6)
* AMIN1: MIN. (line 6)
* AMOD: MOD. (line 6)
* AND: AND. (line 6)
* ANINT: ANINT. (line 6)
* ANY: ANY. (line 6)
* area hyperbolic cosine: ACOSH. (line 6)
* area hyperbolic sine: ASINH. (line 6)
* area hyperbolic tangent: ATANH. (line 6)
* argument list functions: Argument list functions.
(line 6)
* arguments, to program <1>: IARGC. (line 6)
* arguments, to program <2>: GET_COMMAND_ARGUMENT.
(line 6)
* arguments, to program <3>: GET_COMMAND. (line 6)
* arguments, to program <4>: GETARG. (line 6)
* arguments, to program: COMMAND_ARGUMENT_COUNT.
(line 6)
* array, add elements: SUM. (line 6)
* array, apply condition <1>: ANY. (line 6)
* array, apply condition: ALL. (line 6)
* array, bounds checking: Code Gen Options. (line 143)
* array, change dimensions: RESHAPE. (line 6)
* array, combine arrays: MERGE. (line 6)
* array, condition testing <1>: ANY. (line 6)
* array, condition testing: ALL. (line 6)
* array, conditionally add elements: SUM. (line 6)
* array, conditionally count elements: COUNT. (line 6)
* array, conditionally multiply elements: PRODUCT. (line 6)
* array, constructors: Fortran 2003 status. (line 14)
* array, count elements: SIZE. (line 6)
* array, duplicate dimensions: SPREAD. (line 6)
* array, duplicate elements: SPREAD. (line 6)
* array, element counting: COUNT. (line 6)
* array, gather elements: PACK. (line 6)
* array, increase dimension <1>: UNPACK. (line 6)
* array, increase dimension: SPREAD. (line 6)
* array, indices of type real: Real array indices. (line 6)
* array, location of maximum element: MAXLOC. (line 6)
* array, location of minimum element: MINLOC. (line 6)
* array, lower bound: LBOUND. (line 6)
* array, maximum value: MAXVAL. (line 6)
* array, merge arrays: MERGE. (line 6)
* array, minimum value: MINVAL. (line 6)
* array, multiply elements: PRODUCT. (line 6)
* array, number of elements <1>: SIZE. (line 6)
* array, number of elements: COUNT. (line 6)
* array, packing: PACK. (line 6)
* array, permutation: CSHIFT. (line 6)
* array, product: PRODUCT. (line 6)
* array, reduce dimension: PACK. (line 6)
* array, rotate: CSHIFT. (line 6)
* array, scatter elements: UNPACK. (line 6)
* array, shape: SHAPE. (line 6)
* array, shift: EOSHIFT. (line 6)
* array, shift circularly: CSHIFT. (line 6)
* array, size: SIZE. (line 6)
* array, sum: SUM. (line 6)
* array, transmogrify: RESHAPE. (line 6)
* array, transpose: TRANSPOSE. (line 6)
* array, unpacking: UNPACK. (line 6)
* array, upper bound: UBOUND. (line 6)
* ASCII collating sequence <1>: IACHAR. (line 6)
* ASCII collating sequence: ACHAR. (line 6)
* ASIN: ASIN. (line 6)
* ASINH: ASINH. (line 6)
* ASSOCIATED: ASSOCIATED. (line 6)
* association status: ASSOCIATED. (line 6)
* association status, C pointer: C_ASSOCIATED. (line 6)
* ATAN: ATAN. (line 6)
* ATAN2: ATAN2. (line 6)
* ATANH: ATANH. (line 6)
* Authors: Contributors. (line 6)
* backslash: Fortran Dialect Options.
(line 62)
* backtrace: Debugging Options. (line 31)
* BESJ0: BESSEL_J0. (line 6)
* BESJ1: BESSEL_J1. (line 6)
* BESJN: BESSEL_JN. (line 6)
* Bessel function, first kind <1>: BESSEL_JN. (line 6)
* Bessel function, first kind <2>: BESSEL_J1. (line 6)
* Bessel function, first kind: BESSEL_J0. (line 6)
* Bessel function, second kind <1>: BESSEL_YN. (line 6)
* Bessel function, second kind <2>: BESSEL_Y1. (line 6)
* Bessel function, second kind: BESSEL_Y0. (line 6)
* BESSEL_J0: BESSEL_J0. (line 6)
* BESSEL_J1: BESSEL_J1. (line 6)
* BESSEL_JN: BESSEL_JN. (line 6)
* BESSEL_Y0: BESSEL_Y0. (line 6)
* BESSEL_Y1: BESSEL_Y1. (line 6)
* BESSEL_YN: BESSEL_YN. (line 6)
* BESY0: BESSEL_Y0. (line 6)
* BESY1: BESSEL_Y1. (line 6)
* BESYN: BESSEL_YN. (line 6)
* BIT_SIZE: BIT_SIZE. (line 6)
* bits, clear: IBCLR. (line 6)
* bits, extract: IBITS. (line 6)
* bits, get: IBITS. (line 6)
* bits, move <1>: TRANSFER. (line 6)
* bits, move: MVBITS. (line 6)
* bits, negate: NOT. (line 6)
* bits, number of: BIT_SIZE. (line 6)
* bits, set: IBSET. (line 6)
* bits, shift: ISHFT. (line 6)
* bits, shift circular: ISHFTC. (line 6)
* bits, shift left: LSHIFT. (line 6)
* bits, shift right: RSHIFT. (line 6)
* bits, testing: BTEST. (line 6)
* bits, unset: IBCLR. (line 6)
* bitwise logical and <1>: IAND. (line 6)
* bitwise logical and: AND. (line 6)
* bitwise logical exclusive or <1>: XOR. (line 6)
* bitwise logical exclusive or: IEOR. (line 6)
* bitwise logical not: NOT. (line 6)
* bitwise logical or <1>: OR. (line 6)
* bitwise logical or: IOR. (line 6)
* bounds checking: Code Gen Options. (line 143)
* BOZ literal constants: BOZ literal constants.
(line 6)
* BTEST: BTEST. (line 6)
* C_ASSOCIATED: C_ASSOCIATED. (line 6)
* C_F_POINTER: C_F_POINTER. (line 6)
* C_F_PROCPOINTER: C_F_PROCPOINTER. (line 6)
* C_FUNLOC: C_FUNLOC. (line 6)
* C_LOC: C_LOC. (line 6)
* C_SIZEOF: C_SIZEOF. (line 6)
* CABS: ABS. (line 6)
* calling convention: Code Gen Options. (line 25)
* CCOS: COS. (line 6)
* CDABS: ABS. (line 6)
* CDCOS: COS. (line 6)
* CDEXP: EXP. (line 6)
* CDLOG: LOG. (line 6)
* CDSIN: SIN. (line 6)
* CDSQRT: SQRT. (line 6)
* ceiling: CEILING. (line 6)
* CEILING: CEILING. (line 6)
* ceiling: ANINT. (line 6)
* CEXP: EXP. (line 6)
* CHAR: CHAR. (line 6)
* character kind: SELECTED_CHAR_KIND. (line 6)
* character set: Fortran Dialect Options.
(line 56)
* CHDIR: CHDIR. (line 6)
* checking array temporaries: Code Gen Options. (line 143)
* checking subscripts: Code Gen Options. (line 143)
* CHMOD: CHMOD. (line 6)
* clock ticks <1>: SYSTEM_CLOCK. (line 6)
* clock ticks <2>: MCLOCK8. (line 6)
* clock ticks: MCLOCK. (line 6)
* CLOG: LOG. (line 6)
* CMPLX: CMPLX. (line 6)
* code generation, conventions: Code Gen Options. (line 6)
* collating sequence, ASCII <1>: IACHAR. (line 6)
* collating sequence, ASCII: ACHAR. (line 6)
* command options: Invoking GNU Fortran.
(line 6)
* command-line arguments <1>: IARGC. (line 6)
* command-line arguments <2>: GET_COMMAND_ARGUMENT.
(line 6)
* command-line arguments <3>: GET_COMMAND. (line 6)
* command-line arguments <4>: GETARG. (line 6)
* command-line arguments: COMMAND_ARGUMENT_COUNT.
(line 6)
* command-line arguments, number of <1>: IARGC. (line 6)
* command-line arguments, number of: COMMAND_ARGUMENT_COUNT.
(line 6)
* COMMAND_ARGUMENT_COUNT: COMMAND_ARGUMENT_COUNT.
(line 6)
* COMPLEX: COMPLEX. (line 6)
* complex conjugate: CONJG. (line 6)
* complex numbers, conversion to <1>: DCMPLX. (line 6)
* complex numbers, conversion to <2>: COMPLEX. (line 6)
* complex numbers, conversion to: CMPLX. (line 6)
* complex numbers, imaginary part: AIMAG. (line 6)
* complex numbers, real part <1>: REAL. (line 6)
* complex numbers, real part: DREAL. (line 6)
* Conditional compilation: Preprocessing and conditional compilation.
(line 6)
* CONJG: CONJG. (line 6)
* Contributing: Contributing. (line 6)
* Contributors: Contributors. (line 6)
* conversion: Error and Warning Options.
(line 104)
* conversion, to character: CHAR. (line 6)
* conversion, to complex <1>: DCMPLX. (line 6)
* conversion, to complex <2>: COMPLEX. (line 6)
* conversion, to complex: CMPLX. (line 6)
* conversion, to integer <1>: LONG. (line 6)
* conversion, to integer <2>: INT8. (line 6)
* conversion, to integer <3>: INT2. (line 6)
* conversion, to integer <4>: INT. (line 6)
* conversion, to integer <5>: ICHAR. (line 6)
* conversion, to integer <6>: IACHAR. (line 6)
* conversion, to integer: Implicitly convert LOGICAL and INTEGER values.
(line 6)
* conversion, to logical <1>: LOGICAL. (line 6)
* conversion, to logical: Implicitly convert LOGICAL and INTEGER values.
(line 6)
* conversion, to real <1>: SNGL. (line 6)
* conversion, to real <2>: REAL. (line 6)
* conversion, to real <3>: FLOAT. (line 6)
* conversion, to real <4>: DFLOAT. (line 6)
* conversion, to real: DBLE. (line 6)
* conversion, to string: CTIME. (line 6)
* CONVERT specifier: CONVERT specifier. (line 6)
* core, dump <1>: ABORT. (line 6)
* core, dump: Debugging Options. (line 38)
* COS: COS. (line 6)
* COSH: COSH. (line 6)
* cosine: COS. (line 6)
* cosine, hyperbolic: COSH. (line 6)
* cosine, hyperbolic, inverse: ACOSH. (line 6)
* cosine, inverse: ACOS. (line 6)
* COUNT: COUNT. (line 6)
* CPP <1>: Preprocessing Options.
(line 6)
* CPP: Preprocessing and conditional compilation.
(line 6)
* CPU_TIME: CPU_TIME. (line 6)
* Credits: Contributors. (line 6)
* CSHIFT: CSHIFT. (line 6)
* CSIN: SIN. (line 6)
* CSQRT: SQRT. (line 6)
* CTIME: CTIME. (line 6)
* current date <1>: IDATE. (line 6)
* current date <2>: FDATE. (line 6)
* current date: DATE_AND_TIME. (line 6)
* current time <1>: TIME8. (line 6)
* current time <2>: TIME. (line 6)
* current time <3>: ITIME. (line 6)
* current time <4>: FDATE. (line 6)
* current time: DATE_AND_TIME. (line 6)
* DABS: ABS. (line 6)
* DACOS: ACOS. (line 6)
* DACOSH: ACOSH. (line 6)
* DASIN: ASIN. (line 6)
* DASINH: ASINH. (line 6)
* DATAN: ATAN. (line 6)
* DATAN2: ATAN2. (line 6)
* DATANH: ATANH. (line 6)
* date, current <1>: IDATE. (line 6)
* date, current <2>: FDATE. (line 6)
* date, current: DATE_AND_TIME. (line 6)
* DATE_AND_TIME: DATE_AND_TIME. (line 6)
* DBESJ0: BESSEL_J0. (line 6)
* DBESJ1: BESSEL_J1. (line 6)
* DBESJN: BESSEL_JN. (line 6)
* DBESY0: BESSEL_Y0. (line 6)
* DBESY1: BESSEL_Y1. (line 6)
* DBESYN: BESSEL_YN. (line 6)
* DBLE: DBLE. (line 6)
* DCMPLX: DCMPLX. (line 6)
* DCONJG: CONJG. (line 6)
* DCOS: COS. (line 6)
* DCOSH: COSH. (line 6)
* DDIM: DIM. (line 6)
* debugging information options: Debugging Options. (line 6)
* debugging, preprocessor: Preprocessing Options.
(line 26)
* DECODE: ENCODE and DECODE statements.
(line 6)
* DEFERRED procedure binding: Fortran 2003 status. (line 69)
* delayed execution <1>: SLEEP. (line 6)
* delayed execution: ALARM. (line 6)
* derived-type extension: Fortran 2003 status. (line 67)
* DEXP: EXP. (line 6)
* DFLOAT: DFLOAT. (line 6)
* DGAMMA: GAMMA. (line 6)
* dialect options: Fortran Dialect Options.
(line 6)
* DIGITS: DIGITS. (line 6)
* DIM: DIM. (line 6)
* DIMAG: AIMAG. (line 6)
* DINT: AINT. (line 6)
* directive, INCLUDE: Directory Options. (line 6)
* directory, options: Directory Options. (line 6)
* directory, search paths for inclusion: Directory Options. (line 14)
* division, modulo: MODULO. (line 6)
* division, remainder: MOD. (line 6)
* DLGAMA: LOG_GAMMA. (line 6)
* DLOG: LOG. (line 6)
* DLOG10: LOG10. (line 6)
* DMAX1: MAX. (line 6)
* DMIN1: MIN. (line 6)
* DMOD: MOD. (line 6)
* DNINT: ANINT. (line 6)
* dot product: DOT_PRODUCT. (line 6)
* DOT_PRODUCT: DOT_PRODUCT. (line 6)
* DPROD: DPROD. (line 6)
* DREAL: DREAL. (line 6)
* DSIGN: SIGN. (line 6)
* DSIN: SIN. (line 6)
* DSINH: SINH. (line 6)
* DSQRT: SQRT. (line 6)
* DTAN: TAN. (line 6)
* DTANH: TANH. (line 6)
* DTIME: DTIME. (line 6)
* elapsed time <1>: SECOND. (line 6)
* elapsed time <2>: SECNDS. (line 6)
* elapsed time: DTIME. (line 6)
* ENCODE: ENCODE and DECODE statements.
(line 6)
* ENUM statement: Fortran 2003 status. (line 22)
* ENUMERATOR statement: Fortran 2003 status. (line 22)
* environment variable <1>: GET_ENVIRONMENT_VARIABLE.
(line 6)
* environment variable <2>: GETENV. (line 6)
* environment variable <3>: Runtime. (line 6)
* environment variable: Environment Variables.
(line 6)
* EOSHIFT: EOSHIFT. (line 6)
* EPSILON: EPSILON. (line 6)
* ERF: ERF. (line 6)
* ERFC: ERFC. (line 6)
* ERFC_SCALED: ERFC_SCALED. (line 6)
* error function: ERF. (line 6)
* error function, complementary: ERFC. (line 6)
* error function, complementary, exponentially-scaled: ERFC_SCALED.
(line 6)
* errors, limiting: Error and Warning Options.
(line 27)
* escape characters: Fortran Dialect Options.
(line 62)
* ETIME: ETIME. (line 6)
* Euclidean distance: HYPOT. (line 6)
* EXIT: EXIT. (line 6)
* EXP: EXP. (line 6)
* EXPONENT: EXPONENT. (line 6)
* exponential function: EXP. (line 6)
* exponential function, inverse <1>: LOG10. (line 6)
* exponential function, inverse: LOG. (line 6)
* expression size <1>: SIZEOF. (line 6)
* expression size: C_SIZEOF. (line 6)
* EXTENDS: Fortran 2003 status. (line 67)
* extensions: Extensions. (line 6)
* extensions, implemented: Extensions implemented in GNU Fortran.
(line 6)
* extensions, not implemented: Extensions not implemented in GNU Fortran.
(line 6)
* f2c calling convention: Code Gen Options. (line 25)
* Factorial function: GAMMA. (line 6)
* FDATE: FDATE. (line 6)
* FDL, GNU Free Documentation License: GNU Free Documentation License.
(line 6)
* FGET: FGET. (line 6)
* FGETC: FGETC. (line 6)
* file format, fixed: Fortran Dialect Options.
(line 12)
* file format, free: Fortran Dialect Options.
(line 12)
* file operation, file number: FNUM. (line 6)
* file operation, flush: FLUSH. (line 6)
* file operation, position <1>: FTELL. (line 6)
* file operation, position: FSEEK. (line 6)
* file operation, read character <1>: FGETC. (line 6)
* file operation, read character: FGET. (line 6)
* file operation, seek: FSEEK. (line 6)
* file operation, write character <1>: FPUTC. (line 6)
* file operation, write character: FPUT. (line 6)
* file system, access mode: ACCESS. (line 6)
* file system, change access mode: CHMOD. (line 6)
* file system, create link <1>: SYMLNK. (line 6)
* file system, create link: LINK. (line 6)
* file system, file creation mask: UMASK. (line 6)
* file system, file status <1>: STAT. (line 6)
* file system, file status <2>: LSTAT. (line 6)
* file system, file status: FSTAT. (line 6)
* file system, hard link: LINK. (line 6)
* file system, remove file: UNLINK. (line 6)
* file system, rename file: RENAME. (line 6)
* file system, soft link: SYMLNK. (line 6)
* FLOAT: FLOAT. (line 6)
* floating point, exponent: EXPONENT. (line 6)
* floating point, fraction: FRACTION. (line 6)
* floating point, nearest different: NEAREST. (line 6)
* floating point, relative spacing <1>: SPACING. (line 6)
* floating point, relative spacing: RRSPACING. (line 6)
* floating point, scale: SCALE. (line 6)
* floating point, set exponent: SET_EXPONENT. (line 6)
* floor: FLOOR. (line 6)
* FLOOR: FLOOR. (line 6)
* floor: AINT. (line 6)
* FLUSH: FLUSH. (line 6)
* FLUSH statement: Fortran 2003 status. (line 18)
* FNUM: FNUM. (line 6)
* FORMAT: Variable FORMAT expressions.
(line 6)
* Fortran 77: GNU Fortran and G77. (line 6)
* FPP: Preprocessing and conditional compilation.
(line 6)
* FPUT: FPUT. (line 6)
* FPUTC: FPUTC. (line 6)
* FRACTION: FRACTION. (line 6)
* FREE: FREE. (line 6)
* FSEEK: FSEEK. (line 6)
* FSTAT: FSTAT. (line 6)
* FTELL: FTELL. (line 6)
* g77: GNU Fortran and G77. (line 6)
* g77 calling convention: Code Gen Options. (line 25)
* GAMMA: GAMMA. (line 6)
* Gamma function: GAMMA. (line 6)
* Gamma function, logarithm of: LOG_GAMMA. (line 6)
* GCC: GNU Fortran and GCC. (line 6)
* GERROR: GERROR. (line 6)
* GET_COMMAND: GET_COMMAND. (line 6)
* GET_COMMAND_ARGUMENT: GET_COMMAND_ARGUMENT.
(line 6)
* GET_ENVIRONMENT_VARIABLE: GET_ENVIRONMENT_VARIABLE.
(line 6)
* GETARG: GETARG. (line 6)
* GETCWD: GETCWD. (line 6)
* GETENV: GETENV. (line 6)
* GETGID: GETGID. (line 6)
* GETLOG: GETLOG. (line 6)
* GETPID: GETPID. (line 6)
* GETUID: GETUID. (line 6)
* GMTIME: GMTIME. (line 6)
* GNU Compiler Collection: GNU Fortran and GCC. (line 6)
* GNU Fortran command options: Invoking GNU Fortran.
(line 6)
* Hollerith constants: Hollerith constants support.
(line 6)
* HOSTNM: HOSTNM. (line 6)
* HUGE: HUGE. (line 6)
* hyperbolic cosine: COSH. (line 6)
* hyperbolic function, cosine: COSH. (line 6)
* hyperbolic function, cosine, inverse: ACOSH. (line 6)
* hyperbolic function, sine: SINH. (line 6)
* hyperbolic function, sine, inverse: ASINH. (line 6)
* hyperbolic function, tangent: TANH. (line 6)
* hyperbolic function, tangent, inverse: ATANH. (line 6)
* hyperbolic sine: SINH. (line 6)
* hyperbolic tangent: TANH. (line 6)
* HYPOT: HYPOT. (line 6)
* I/O item lists: I/O item lists. (line 6)
* IABS: ABS. (line 6)
* IACHAR: IACHAR. (line 6)
* IAND: IAND. (line 6)
* IARGC: IARGC. (line 6)
* IBCLR: IBCLR. (line 6)
* IBITS: IBITS. (line 6)
* IBSET: IBSET. (line 6)
* ICHAR: ICHAR. (line 6)
* IDATE: IDATE. (line 6)
* IDIM: DIM. (line 6)
* IDINT: INT. (line 6)
* IDNINT: NINT. (line 6)
* IEEE, ISNAN: ISNAN. (line 6)
* IEOR: IEOR. (line 6)
* IERRNO: IERRNO. (line 6)
* IFIX: INT. (line 6)
* IMAG: AIMAG. (line 6)
* IMAGPART: AIMAG. (line 6)
* IMPORT statement: Fortran 2003 status. (line 51)
* INCLUDE directive: Directory Options. (line 6)
* inclusion, directory search paths for: Directory Options. (line 14)
* INDEX: INDEX intrinsic. (line 6)
* INT: INT. (line 6)
* INT2: INT2. (line 6)
* INT8: INT8. (line 6)
* integer kind: SELECTED_INT_KIND. (line 6)
* Interoperability: Mixed-Language Programming.
(line 6)
* intrinsic: Error and Warning Options.
(line 158)
* intrinsic Modules: Intrinsic Modules. (line 6)
* intrinsic procedures: Intrinsic Procedures.
(line 6)
* Introduction: Top. (line 6)
* inverse hyperbolic cosine: ACOSH. (line 6)
* inverse hyperbolic sine: ASINH. (line 6)
* inverse hyperbolic tangent: ATANH. (line 6)
* IOMSG= specifier: Fortran 2003 status. (line 20)
* IOR: IOR. (line 6)
* IOSTAT, end of file: IS_IOSTAT_END. (line 6)
* IOSTAT, end of record: IS_IOSTAT_EOR. (line 6)
* IRAND: IRAND. (line 6)
* IS_IOSTAT_END: IS_IOSTAT_END. (line 6)
* IS_IOSTAT_EOR: IS_IOSTAT_EOR. (line 6)
* ISATTY: ISATTY. (line 6)
* ISHFT: ISHFT. (line 6)
* ISHFTC: ISHFTC. (line 6)
* ISIGN: SIGN. (line 6)
* ISNAN: ISNAN. (line 6)
* ISO C Bindings: Fortran 2003 status. (line 60)
* ISO_FORTRAN_ENV statement: Fortran 2003 status. (line 54)
* ITIME: ITIME. (line 6)
* KILL: KILL. (line 6)
* kind: KIND. (line 6)
* KIND: KIND. (line 6)
* kind: KIND Type Parameters.
(line 6)
* kind, character: SELECTED_CHAR_KIND. (line 6)
* kind, integer: SELECTED_INT_KIND. (line 6)
* kind, old-style: Old-style kind specifications.
(line 6)
* kind, real: SELECTED_REAL_KIND. (line 6)
* language, dialect options: Fortran Dialect Options.
(line 6)
* LBOUND: LBOUND. (line 6)
* LEADZ: LEADZ. (line 6)
* LEN: LEN. (line 6)
* LEN_TRIM: LEN_TRIM. (line 6)
* lexical comparison of strings <1>: LLT. (line 6)
* lexical comparison of strings <2>: LLE. (line 6)
* lexical comparison of strings <3>: LGT. (line 6)
* lexical comparison of strings: LGE. (line 6)
* LGAMMA: LOG_GAMMA. (line 6)
* LGE: LGE. (line 6)
* LGT: LGT. (line 6)
* libf2c calling convention: Code Gen Options. (line 25)
* libgfortran initialization, set_args: _gfortran_set_args. (line 6)
* libgfortran initialization, set_convert: _gfortran_set_convert.
(line 6)
* libgfortran initialization, set_fpe: _gfortran_set_fpe. (line 6)
* libgfortran initialization, set_max_subrecord_length: _gfortran_set_max_subrecord_length.
(line 6)
* libgfortran initialization, set_options: _gfortran_set_options.
(line 6)
* libgfortran initialization, set_record_marker: _gfortran_set_record_marker.
(line 6)
* limits, largest number: HUGE. (line 6)
* limits, smallest number: TINY. (line 6)
* LINK: LINK. (line 6)
* linking, static: Link Options. (line 6)
* LLE: LLE. (line 6)
* LLT: LLT. (line 6)
* LNBLNK: LNBLNK. (line 6)
* LOC: LOC. (line 6)
* location of a variable in memory: LOC. (line 6)
* LOG: LOG. (line 6)
* LOG10: LOG10. (line 6)
* LOG_GAMMA: LOG_GAMMA. (line 6)
* logarithmic function <1>: LOG10. (line 6)
* logarithmic function: LOG. (line 6)
* logarithmic function, inverse: EXP. (line 6)
* LOGICAL: LOGICAL. (line 6)
* logical and, bitwise <1>: IAND. (line 6)
* logical and, bitwise: AND. (line 6)
* logical exclusive or, bitwise <1>: XOR. (line 6)
* logical exclusive or, bitwise: IEOR. (line 6)
* logical not, bitwise: NOT. (line 6)
* logical or, bitwise <1>: OR. (line 6)
* logical or, bitwise: IOR. (line 6)
* logical, variable representation: Internal representation of LOGICAL variables.
(line 6)
* login name: GETLOG. (line 6)
* LONG: LONG. (line 6)
* LSHIFT: LSHIFT. (line 6)
* LSTAT: LSTAT. (line 6)
* LTIME: LTIME. (line 6)
* MALLOC: MALLOC. (line 6)
* MATMUL: MATMUL. (line 6)
* matrix multiplication: MATMUL. (line 6)
* matrix, transpose: TRANSPOSE. (line 6)
* MAX: MAX. (line 6)
* MAX0: MAX. (line 6)
* MAX1: MAX. (line 6)
* MAXEXPONENT: MAXEXPONENT. (line 6)
* maximum value <1>: MAXVAL. (line 6)
* maximum value: MAX. (line 6)
* MAXLOC: MAXLOC. (line 6)
* MAXVAL: MAXVAL. (line 6)
* MCLOCK: MCLOCK. (line 6)
* MCLOCK8: MCLOCK8. (line 6)
* memory checking: Code Gen Options. (line 143)
* MERGE: MERGE. (line 6)
* messages, error: Error and Warning Options.
(line 6)
* messages, warning: Error and Warning Options.
(line 6)
* MIN: MIN. (line 6)
* MIN0: MIN. (line 6)
* MIN1: MIN. (line 6)
* MINEXPONENT: MINEXPONENT. (line 6)
* minimum value <1>: MINVAL. (line 6)
* minimum value: MIN. (line 6)
* MINLOC: MINLOC. (line 6)
* MINVAL: MINVAL. (line 6)
* Mixed-language programming: Mixed-Language Programming.
(line 6)
* MOD: MOD. (line 6)
* model representation, base: RADIX. (line 6)
* model representation, epsilon: EPSILON. (line 6)
* model representation, largest number: HUGE. (line 6)
* model representation, maximum exponent: MAXEXPONENT. (line 6)
* model representation, minimum exponent: MINEXPONENT. (line 6)
* model representation, precision: PRECISION. (line 6)
* model representation, radix: RADIX. (line 6)
* model representation, range: RANGE. (line 6)
* model representation, significant digits: DIGITS. (line 6)
* model representation, smallest number: TINY. (line 6)
* module entities: Fortran Dialect Options.
(line 74)
* module search path: Directory Options. (line 14)
* modulo: MODULO. (line 6)
* MODULO: MODULO. (line 6)
* MOVE_ALLOC: MOVE_ALLOC. (line 6)
* moving allocation: MOVE_ALLOC. (line 6)
* multiply array elements: PRODUCT. (line 6)
* MVBITS: MVBITS. (line 6)
* Namelist: Extensions to namelist.
(line 6)
* NEAREST: NEAREST. (line 6)
* NEW_LINE: NEW_LINE. (line 6)
* newline: NEW_LINE. (line 6)
* NINT: NINT. (line 6)
* NOT: NOT. (line 6)
* NULL: NULL. (line 6)
* OpenMP <1>: OpenMP. (line 6)
* OpenMP: Fortran Dialect Options.
(line 112)
* operators, unary: Unary operators. (line 6)
* options, code generation: Code Gen Options. (line 6)
* options, debugging: Debugging Options. (line 6)
* options, dialect: Fortran Dialect Options.
(line 6)
* options, directory search: Directory Options. (line 6)
* options, errors: Error and Warning Options.
(line 6)
* options, fortran dialect: Fortran Dialect Options.
(line 12)
* options, gfortran command: Invoking GNU Fortran.
(line 6)
* options, linking: Link Options. (line 6)
* options, negative forms: Invoking GNU Fortran.
(line 13)
* options, preprocessor: Preprocessing Options.
(line 6)
* options, run-time: Code Gen Options. (line 6)
* options, runtime: Runtime Options. (line 6)
* options, warnings: Error and Warning Options.
(line 6)
* OR: OR. (line 6)
* output, newline: NEW_LINE. (line 6)
* PACK: PACK. (line 6)
* paths, search: Directory Options. (line 14)
* PERROR: PERROR. (line 6)
* pointer checking: Code Gen Options. (line 143)
* pointer, C address of pointers: C_F_PROCPOINTER. (line 6)
* pointer, C address of procedures: C_FUNLOC. (line 6)
* pointer, C association status: C_ASSOCIATED. (line 6)
* pointer, convert C to Fortran: C_F_POINTER. (line 6)
* pointer, cray <1>: MALLOC. (line 6)
* pointer, cray: FREE. (line 6)
* pointer, Cray: Cray pointers. (line 6)
* pointer, disassociated: NULL. (line 6)
* pointer, status <1>: NULL. (line 6)
* pointer, status: ASSOCIATED. (line 6)
* positive difference: DIM. (line 6)
* PRECISION: PRECISION. (line 6)
* Preprocessing: Preprocessing and conditional compilation.
(line 6)
* preprocessing, assertation: Preprocessing Options.
(line 114)
* preprocessing, define macros: Preprocessing Options.
(line 153)
* preprocessing, include path: Preprocessing Options.
(line 70)
* preprocessing, keep comments: Preprocessing Options.
(line 123)
* preprocessing, no linemarkers: Preprocessing Options.
(line 181)
* preprocessing, undefine macros: Preprocessing Options.
(line 187)
* preprocessor: Preprocessing Options.
(line 6)
* preprocessor, debugging: Preprocessing Options.
(line 26)
* preprocessor, disable: Preprocessing Options.
(line 13)
* preprocessor, enable: Preprocessing Options.
(line 13)
* preprocessor, include file handling: Preprocessing and conditional compilation.
(line 6)
* preprocessor, working directory: Preprocessing Options.
(line 55)
* PRESENT: PRESENT. (line 6)
* private: Fortran Dialect Options.
(line 74)
* procedure pointer, convert C to Fortran: C_LOC. (line 6)
* process id: GETPID. (line 6)
* PRODUCT: PRODUCT. (line 6)
* product, double-precision: DPROD. (line 6)
* product, matrix: MATMUL. (line 6)
* product, vector: DOT_PRODUCT. (line 6)
* program termination: EXIT. (line 6)
* program termination, with core dump: ABORT. (line 6)
* PROTECTED statement: Fortran 2003 status. (line 45)
* RADIX: RADIX. (line 6)
* RAN: RAN. (line 6)
* RAND: RAND. (line 6)
* random number generation <1>: RANDOM_NUMBER. (line 6)
* random number generation <2>: RAND. (line 6)
* random number generation <3>: RAN. (line 6)
* random number generation: IRAND. (line 6)
* random number generation, seeding <1>: SRAND. (line 6)
* random number generation, seeding: RANDOM_SEED. (line 6)
* RANDOM_NUMBER: RANDOM_NUMBER. (line 6)
* RANDOM_SEED: RANDOM_SEED. (line 6)
* RANGE: RANGE. (line 6)
* range checking: Code Gen Options. (line 143)
* re-association of parenthesed expressions: Code Gen Options.
(line 315)
* read character, stream mode <1>: FGETC. (line 6)
* read character, stream mode: FGET. (line 6)
* REAL: REAL. (line 6)
* real kind: SELECTED_REAL_KIND. (line 6)
* real number, exponent: EXPONENT. (line 6)
* real number, fraction: FRACTION. (line 6)
* real number, nearest different: NEAREST. (line 6)
* real number, relative spacing <1>: SPACING. (line 6)
* real number, relative spacing: RRSPACING. (line 6)
* real number, scale: SCALE. (line 6)
* real number, set exponent: SET_EXPONENT. (line 6)
* REALPART: REAL. (line 6)
* RECORD: STRUCTURE and RECORD.
(line 6)
* remainder: MOD. (line 6)
* RENAME: RENAME. (line 6)
* repacking arrays: Code Gen Options. (line 236)
* REPEAT: REPEAT. (line 6)
* RESHAPE: RESHAPE. (line 6)
* root: SQRT. (line 6)
* rounding, ceiling <1>: CEILING. (line 6)
* rounding, ceiling: ANINT. (line 6)
* rounding, floor <1>: FLOOR. (line 6)
* rounding, floor: AINT. (line 6)
* rounding, nearest whole number: NINT. (line 6)
* RRSPACING: RRSPACING. (line 6)
* RSHIFT: RSHIFT. (line 6)
* run-time checking: Code Gen Options. (line 143)
* SAVE statement: Code Gen Options. (line 15)
* SCALE: SCALE. (line 6)
* SCAN: SCAN. (line 6)
* search path: Directory Options. (line 6)
* search paths, for included files: Directory Options. (line 14)
* SECNDS: SECNDS. (line 6)
* SECOND: SECOND. (line 6)
* seeding a random number generator <1>: SRAND. (line 6)
* seeding a random number generator: RANDOM_SEED. (line 6)
* SELECTED_CHAR_KIND: SELECTED_CHAR_KIND. (line 6)
* SELECTED_INT_KIND: SELECTED_INT_KIND. (line 6)
* SELECTED_REAL_KIND: SELECTED_REAL_KIND. (line 6)
* SET_EXPONENT: SET_EXPONENT. (line 6)
* SHAPE: SHAPE. (line 6)
* SHORT: INT2. (line 6)
* SIGN: SIGN. (line 6)
* sign copying: SIGN. (line 6)
* SIGNAL: SIGNAL. (line 6)
* SIN: SIN. (line 6)
* sine: SIN. (line 6)
* sine, hyperbolic: SINH. (line 6)
* sine, hyperbolic, inverse: ASINH. (line 6)
* sine, inverse: ASIN. (line 6)
* SINH: SINH. (line 6)
* SIZE: SIZE. (line 6)
* size of a variable, in bits: BIT_SIZE. (line 6)
* size of an expression <1>: SIZEOF. (line 6)
* size of an expression: C_SIZEOF. (line 6)
* SIZEOF: SIZEOF. (line 6)
* SLEEP: SLEEP. (line 6)
* SNGL: SNGL. (line 6)
* SPACING: SPACING. (line 6)
* SPREAD: SPREAD. (line 6)
* SQRT: SQRT. (line 6)
* square-root: SQRT. (line 6)
* SRAND: SRAND. (line 6)
* Standards: Standards. (line 6)
* STAT: STAT. (line 6)
* statement, ENUM: Fortran 2003 status. (line 22)
* statement, ENUMERATOR: Fortran 2003 status. (line 22)
* statement, FLUSH: Fortran 2003 status. (line 18)
* statement, IMPORT: Fortran 2003 status. (line 51)
* statement, ISO_FORTRAN_ENV: Fortran 2003 status. (line 54)
* statement, PROTECTED: Fortran 2003 status. (line 45)
* statement, SAVE: Code Gen Options. (line 15)
* statement, USE, INTRINSIC: Fortran 2003 status. (line 54)
* statement, VALUE: Fortran 2003 status. (line 47)
* statement, VOLATILE: Fortran 2003 status. (line 49)
* STREAM I/O: Fortran 2003 status. (line 40)
* stream mode, read character <1>: FGETC. (line 6)
* stream mode, read character: FGET. (line 6)
* stream mode, write character <1>: FPUTC. (line 6)
* stream mode, write character: FPUT. (line 6)
* string, adjust left: ADJUSTL. (line 6)
* string, adjust right: ADJUSTR. (line 6)
* string, comparison <1>: LLT. (line 6)
* string, comparison <2>: LLE. (line 6)
* string, comparison <3>: LGT. (line 6)
* string, comparison: LGE. (line 6)
* string, concatenate: REPEAT. (line 6)
* string, find missing set: VERIFY. (line 6)
* string, find non-blank character: LNBLNK. (line 6)
* string, find subset: SCAN. (line 6)
* string, find substring: INDEX intrinsic. (line 6)
* string, length: LEN. (line 6)
* string, length, without trailing whitespace: LEN_TRIM. (line 6)
* string, remove trailing whitespace: TRIM. (line 6)
* string, repeat: REPEAT. (line 6)
* strings, varying length: Varying Length Character Strings.
(line 6)
* STRUCTURE: STRUCTURE and RECORD.
(line 6)
* structure packing: Code Gen Options. (line 230)
* subscript checking: Code Gen Options. (line 143)
* substring position: INDEX intrinsic. (line 6)
* SUM: SUM. (line 6)
* sum array elements: SUM. (line 6)
* suppressing warnings: Error and Warning Options.
(line 6)
* symbol names: Fortran Dialect Options.
(line 56)
* symbol names, transforming: Code Gen Options. (line 54)
* symbol names, underscores: Code Gen Options. (line 54)
* SYMLNK: SYMLNK. (line 6)
* syntax checking: Error and Warning Options.
(line 33)
* SYSTEM: SYSTEM. (line 6)
* system, error handling <1>: PERROR. (line 6)
* system, error handling <2>: IERRNO. (line 6)
* system, error handling: GERROR. (line 6)
* system, group id: GETGID. (line 6)
* system, host name: HOSTNM. (line 6)
* system, login name: GETLOG. (line 6)
* system, process id: GETPID. (line 6)
* system, signal handling: SIGNAL. (line 6)
* system, system call: SYSTEM. (line 6)
* system, terminal <1>: TTYNAM. (line 6)
* system, terminal: ISATTY. (line 6)
* system, user id: GETUID. (line 6)
* system, working directory <1>: GETCWD. (line 6)
* system, working directory: CHDIR. (line 6)
* SYSTEM_CLOCK: SYSTEM_CLOCK. (line 6)
* tabulators: Error and Warning Options.
(line 146)
* TAN: TAN. (line 6)
* tangent: TAN. (line 6)
* tangent, hyperbolic: TANH. (line 6)
* tangent, hyperbolic, inverse: ATANH. (line 6)
* tangent, inverse <1>: ATAN2. (line 6)
* tangent, inverse: ATAN. (line 6)
* TANH: TANH. (line 6)
* terminate program: EXIT. (line 6)
* terminate program, with core dump: ABORT. (line 6)
* TIME: TIME. (line 6)
* time, clock ticks <1>: SYSTEM_CLOCK. (line 6)
* time, clock ticks <2>: MCLOCK8. (line 6)
* time, clock ticks: MCLOCK. (line 6)
* time, conversion to GMT info: GMTIME. (line 6)
* time, conversion to local time info: LTIME. (line 6)
* time, conversion to string: CTIME. (line 6)
* time, current <1>: TIME8. (line 6)
* time, current <2>: TIME. (line 6)
* time, current <3>: ITIME. (line 6)
* time, current <4>: FDATE. (line 6)
* time, current: DATE_AND_TIME. (line 6)
* time, elapsed <1>: SECOND. (line 6)
* time, elapsed <2>: SECNDS. (line 6)
* time, elapsed <3>: ETIME. (line 6)
* time, elapsed <4>: DTIME. (line 6)
* time, elapsed: CPU_TIME. (line 6)
* TIME8: TIME8. (line 6)
* TINY: TINY. (line 6)
* TR 15581: Fortran 2003 status. (line 27)
* trace: Debugging Options. (line 31)
* TRAILZ: TRAILZ. (line 6)
* TRANSFER: TRANSFER. (line 6)
* transforming symbol names: Code Gen Options. (line 54)
* transpose: TRANSPOSE. (line 6)
* TRANSPOSE: TRANSPOSE. (line 6)
* trigonometric function, cosine: COS. (line 6)
* trigonometric function, cosine, inverse: ACOS. (line 6)
* trigonometric function, sine: SIN. (line 6)
* trigonometric function, sine, inverse: ASIN. (line 6)
* trigonometric function, tangent: TAN. (line 6)
* trigonometric function, tangent, inverse <1>: ATAN2. (line 6)
* trigonometric function, tangent, inverse: ATAN. (line 6)
* TRIM: TRIM. (line 6)
* TTYNAM: TTYNAM. (line 6)
* type cast: TRANSFER. (line 6)
* type-bound operator: Fortran 2003 status. (line 64)
* type-bound procedure: Fortran 2003 status. (line 64)
* UBOUND: UBOUND. (line 6)
* UMASK: UMASK. (line 6)
* underflow: Error and Warning Options.
(line 154)
* underscore: Code Gen Options. (line 54)
* UNLINK: UNLINK. (line 6)
* UNPACK: UNPACK. (line 6)
* unused parameter: Error and Warning Options.
(line 164)
* USE, INTRINSIC statement: Fortran 2003 status. (line 54)
* user id: GETUID. (line 6)
* VALUE statement: Fortran 2003 status. (line 47)
* Varying length character strings: Varying Length Character Strings.
(line 6)
* Varying length strings: Varying Length Character Strings.
(line 6)
* vector product: DOT_PRODUCT. (line 6)
* VERIFY: VERIFY. (line 6)
* VOLATILE statement: Fortran 2003 status. (line 49)
* warnings, aliasing: Error and Warning Options.
(line 68)
* warnings, alignment of COMMON blocks: Error and Warning Options.
(line 171)
* warnings, all: Error and Warning Options.
(line 61)
* warnings, ampersand: Error and Warning Options.
(line 85)
* warnings, array temporaries: Error and Warning Options.
(line 93)
* warnings, character truncation: Error and Warning Options.
(line 98)
* warnings, conversion: Error and Warning Options.
(line 104)
* warnings, implicit interface: Error and Warning Options.
(line 107)
* warnings, implicit procedure: Error and Warning Options.
(line 113)
* warnings, intrinsic: Error and Warning Options.
(line 158)
* warnings, intrinsics of other standards: Error and Warning Options.
(line 117)
* warnings, line truncation: Error and Warning Options.
(line 101)
* warnings, non-standard intrinsics: Error and Warning Options.
(line 117)
* warnings, suppressing: Error and Warning Options.
(line 6)
* warnings, suspicious code: Error and Warning Options.
(line 124)
* warnings, tabs: Error and Warning Options.
(line 146)
* warnings, to errors: Error and Warning Options.
(line 177)
* warnings, underflow: Error and Warning Options.
(line 154)
* warnings, unused parameter: Error and Warning Options.
(line 164)
* write character, stream mode <1>: FPUTC. (line 6)
* write character, stream mode: FPUT. (line 6)
* XOR: XOR. (line 6)
* ZABS: ABS. (line 6)
* ZCOS: COS. (line 6)
* zero bits <1>: TRAILZ. (line 6)
* zero bits: LEADZ. (line 6)
* ZEXP: EXP. (line 6)
* ZLOG: LOG. (line 6)
* ZSIN: SIN. (line 6)
* ZSQRT: SQRT. (line 6)

Tag Table:
Node: Top2107
Node: Introduction3485
Node: About GNU Fortran4232
Node: GNU Fortran and GCC8219
Node: Preprocessing and conditional compilation10331
Node: GNU Fortran and G7711972
Node: Project Status12545
Node: Standards15077
Node: Varying Length Character Strings16473
Node: Invoking GNU Fortran17007
Node: Option Summary18730
Node: Fortran Dialect Options22342
Node: Preprocessing Options29380
Node: Error and Warning Options37506
Node: Debugging Options45140
Node: Directory Options47303
Node: Link Options48738
Node: Runtime Options49362
Node: Code Gen Options51611
Node: Environment Variables66371
Node: Runtime66976
Node: GFORTRAN_STDIN_UNIT68204
Node: GFORTRAN_STDOUT_UNIT68571
Node: GFORTRAN_STDERR_UNIT68972
Node: GFORTRAN_USE_STDERR69370
Node: GFORTRAN_TMPDIR69815
Node: GFORTRAN_UNBUFFERED_ALL70256
Node: GFORTRAN_UNBUFFERED_PRECONNECTED70779
Node: GFORTRAN_SHOW_LOCUS71421
Node: GFORTRAN_OPTIONAL_PLUS71915
Node: GFORTRAN_DEFAULT_RECL72390
Node: GFORTRAN_LIST_SEPARATOR72881
Node: GFORTRAN_CONVERT_UNIT73490
Node: GFORTRAN_ERROR_DUMPCORE76352
Node: GFORTRAN_ERROR_BACKTRACE76899
Node: Fortran 2003 and 2008 status77450
Node: Fortran 2003 status77690
Node: Fortran 2008 status80059
Node: Compiler Characteristics81160
Node: KIND Type Parameters81635
Node: Internal representation of LOGICAL variables82615
Node: Extensions83926
Node: Extensions implemented in GNU Fortran84527
Node: Old-style kind specifications85861
Node: Old-style variable initialization86967
Node: Extensions to namelist88279
Node: X format descriptor without count field90275
Node: Commas in FORMAT specifications90802
Node: Missing period in FORMAT specifications91319
Node: I/O item lists91881
Node: BOZ literal constants92270
Node: Real array indices94840
Node: Unary operators95137
Node: Implicitly convert LOGICAL and INTEGER values95551
Node: Hollerith constants support96511
Node: Cray pointers98283
Node: CONVERT specifier103693
Node: OpenMP105691
Node: Argument list functions107938
Node: Extensions not implemented in GNU Fortran109542
Node: STRUCTURE and RECORD110426
Node: ENCODE and DECODE statements112482
Node: Variable FORMAT expressions113840
Node: Mixed-Language Programming114897
Node: Interoperability with C115440
Node: Intrinsic Types116747
Node: Derived Types and struct117278
Node: Interoperable Global Variables118659
Node: Interoperable Subroutines and Functions119931
Node: Further Interoperability of Fortran with C124484
Node: GNU Fortran Compiler Directives125490
Node: Non-Fortran Main Program127687
Node: _gfortran_set_args129825
Node: _gfortran_set_options130759
Node: _gfortran_set_convert133595
Node: _gfortran_set_record_marker134459
Node: _gfortran_set_fpe135283
Node: _gfortran_set_max_subrecord_length136495
Node: Intrinsic Procedures137450
Node: Introduction to Intrinsics151155
Node: ABORT153507
Node: ABS154264
Node: ACCESS155766
Node: ACHAR157687
Node: ACOS158888
Node: ACOSH160010
Node: ADJUSTL160998
Node: ADJUSTR161939
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Node: AINT164206
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Node: BESSEL_JN185727
Node: BESSEL_Y0186942
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Node: C_FUNLOC193085
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Node: C_SIZEOF198490
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Node: CPU_TIME213805
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Node: CTIME216815
Node: DATE_AND_TIME218074
Node: DBLE220535
Node: DCMPLX221359
Node: DFLOAT222553
Node: DIGITS223247
Node: DIM224213
Node: DOT_PRODUCT225356
Node: DPROD227012
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Node: SECOND372139
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Node: SLEEP386342
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Node: STAT392134
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Node: TANH401012
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Node: TRANSFER405674
Node: TRANSPOSE407708
Node: TRIM408395
Node: TTYNAM409252
Node: UBOUND410167
Node: UMASK411536
Node: UNLINK412207
Node: UNPACK413184
Node: VERIFY414472
Node: XOR416188
Node: Intrinsic Modules417560
Node: ISO_FORTRAN_ENV417803
Node: ISO_C_BINDING419448
Node: OpenMP Modules OMP_LIB and OMP_LIB_KINDS423117
Node: Contributing424077
Node: Contributors424929
Node: Projects426596
Node: Proposed Extensions427399
Node: Copying429410
Node: GNU Free Documentation License466974
Node: Funding489386
Node: Option Index491911
Node: Keyword Index504153

End Tag Table