X format descriptor without count field
FORMAT specifications
FORMAT specifications
Q exponent-letter
LOGICAL and INTEGER values
CONVERT specifier
%VAL, %REF and %LOC
_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_fpe — Enable floating point exception traps
_gfortran_set_max_subrecord_length — Set subrecord length
ABORT — Abort the program
ABS — Absolute value
ACCESS — Checks file access modes
ACHAR — Character in ASCII collating sequence
ACOS — Arccosine function
ACOSH — Inverse hyperbolic cosine function
ADJUSTL — Left adjust a string
ADJUSTR — Right adjust a string
AIMAG — Imaginary part of complex number
AINT — Truncate to a whole number
ALARM — Execute a routine after a given delay
ALL — All values in MASK along DIM are true
ALLOCATED — Status of an allocatable entity
AND — Bitwise logical AND
ANINT — Nearest whole number
ANY — Any value in MASK along DIM is true
ASIN — Arcsine function
ASINH — Inverse hyperbolic sine function
ASSOCIATED — Status of a pointer or pointer/target pair
ATAN — Arctangent function
ATAN2 — Arctangent function
ATANH — Inverse hyperbolic tangent function
ATOMIC_DEFINE — Setting a variable atomically
ATOMIC_REF — Obtaining the value of a variable atomically
BACKTRACE — Show a backtrace
BESSEL_J0 — Bessel function of the first kind of order 0
BESSEL_J1 — Bessel function of the first kind of order 1
BESSEL_JN — Bessel function of the first kind
BESSEL_Y0 — Bessel function of the second kind of order 0
BESSEL_Y1 — Bessel function of the second kind of order 1
BESSEL_YN — Bessel function of the second kind
BGE — Bitwise greater than or equal to
BGT — Bitwise greater than
BIT_SIZE — Bit size inquiry function
BLE — Bitwise less than or equal to
BLT — Bitwise less than
BTEST — Bit test function
C_ASSOCIATED — Status of a C pointer
C_F_POINTER — Convert C into Fortran pointer
C_F_PROCPOINTER — Convert C into Fortran procedure pointer
C_FUNLOC — Obtain the C address of a procedure
C_LOC — Obtain the C address of an object
C_SIZEOF — Size in bytes of an expression
CEILING — Integer ceiling function
CHAR — Character conversion function
CHDIR — Change working directory
CHMOD — Change access permissions of files
CMPLX — Complex conversion function
COMMAND_ARGUMENT_COUNT — Get number of command line arguments
COMPILER_OPTIONS — Options passed to the compiler
COMPILER_VERSION — Compiler version string
COMPLEX — Complex conversion function
CONJG — Complex conjugate function
COS — Cosine function
COSH — Hyperbolic cosine function
COUNT — Count function
CPU_TIME — CPU elapsed time in seconds
CSHIFT — Circular shift elements of an array
CTIME — Convert a time into a string
DATE_AND_TIME — Date and time subroutine
DBLE — Double conversion function
DCMPLX — Double complex conversion function
DIGITS — Significant binary digits function
DIM — Positive difference
DOT_PRODUCT — Dot product function
DPROD — Double product function
DREAL — Double real part function
DSHIFTL — Combined left shift
DSHIFTR — Combined right shift
DTIME — Execution time subroutine (or function)
EOSHIFT — End-off shift elements of an array
EPSILON — Epsilon function
ERF — Error function
ERFC — Error function
ERFC_SCALED — Error function
ETIME — Execution time subroutine (or function)
EXECUTE_COMMAND_LINE — Execute a shell command
EXIT — Exit the program with status.
EXP — Exponential function
EXPONENT — Exponent function
EXTENDS_TYPE_OF — Query dynamic type for extension
FDATE — Get the current time as a string
FGET — Read a single character in stream mode from stdin
FGETC — Read a single character in stream mode
FLOOR — Integer floor function
FLUSH — Flush I/O unit(s)
FNUM — File number function
FPUT — Write a single character in stream mode to stdout
FPUTC — Write a single character in stream mode
FRACTION — Fractional part of the model representation
FREE — Frees memory
FSEEK — Low level file positioning subroutine
FSTAT — Get file status
FTELL — Current stream position
GAMMA — Gamma function
GERROR — Get last system error message
GETARG — Get command line arguments
GET_COMMAND — Get the entire command line
GET_COMMAND_ARGUMENT — Get command line arguments
GETCWD — Get current working directory
GETENV — Get an environmental variable
GET_ENVIRONMENT_VARIABLE — Get an environmental variable
GETGID — Group ID function
GETLOG — Get login name
GETPID — Process ID function
GETUID — User ID function
GMTIME — Convert time to GMT info
HOSTNM — Get system host name
HUGE — Largest number of a kind
HYPOT — Euclidean distance function
IACHAR — Code in ASCII collating sequence
IALL — Bitwise AND of array elements
IAND — Bitwise logical and
IANY — Bitwise OR of array elements
IARGC — Get the number of command line arguments
IBCLR — Clear bit
IBITS — Bit extraction
IBSET — Set bit
ICHAR — Character-to-integer conversion function
IDATE — Get current local time subroutine (day/month/year)
IEOR — Bitwise logical exclusive or
IERRNO — Get the last system error number
IMAGE_INDEX — Function that converts a cosubscript to an image index
INDEX — Position of a substring within a string
INT — Convert to integer type
INT2 — Convert to 16-bit integer type
INT8 — Convert to 64-bit integer type
IOR — Bitwise logical or
IPARITY — Bitwise XOR of array elements
IRAND — Integer pseudo-random number
IS_IOSTAT_END — Test for end-of-file value
IS_IOSTAT_EOR — Test for end-of-record value
ISATTY — Whether a unit is a terminal device.
ISHFT — Shift bits
ISHFTC — Shift bits circularly
ISNAN — Test for a NaN
ITIME — Get current local time subroutine (hour/minutes/seconds)
KILL — Send a signal to a process
KIND — Kind of an entity
LBOUND — Lower dimension bounds of an array
LCOBOUND — Lower codimension bounds of an array
LEADZ — Number of leading zero bits of an integer
LEN — Length of a character entity
LEN_TRIM — Length of a character entity without trailing blank characters
LGE — Lexical greater than or equal
LGT — Lexical greater than
LINK — Create a hard link
LLE — Lexical less than or equal
LLT — Lexical less than
LNBLNK — Index of the last non-blank character in a string
LOC — Returns the address of a variable
LOG — Natural logarithm function
LOG10 — Base 10 logarithm function
LOG_GAMMA — Logarithm of the Gamma function
LOGICAL — Convert to logical type
LONG — Convert to integer type
LSHIFT — Left shift bits
LSTAT — Get file status
LTIME — Convert time to local time info
MALLOC — Allocate dynamic memory
MASKL — Left justified mask
MASKR — Right justified mask
MATMUL — matrix multiplication
MAX — Maximum value of an argument list
MAXEXPONENT — Maximum exponent of a real kind
MAXLOC — Location of the maximum value within an array
MAXVAL — Maximum value of an array
MCLOCK — Time function
MCLOCK8 — Time function (64-bit)
MERGE — Merge variables
MERGE_BITS — Merge of bits under mask
MIN — Minimum value of an argument list
MINEXPONENT — Minimum exponent of a real kind
MINLOC — Location of the minimum value within an array
MINVAL — Minimum value of an array
MOD — Remainder function
MODULO — Modulo function
MOVE_ALLOC — Move allocation from one object to another
MVBITS — Move bits from one integer to another
NEAREST — Nearest representable number
NEW_LINE — New line character
NINT — Nearest whole number
NORM2 — Euclidean vector norms
NOT — Logical negation
NULL — Function that returns an disassociated pointer
NUM_IMAGES — Function that returns the number of images
OR — Bitwise logical OR
PACK — Pack an array into an array of rank one
PARITY — Reduction with exclusive OR
PERROR — Print system error message
POPCNT — Number of bits set
POPPAR — Parity of the number of bits set
PRECISION — Decimal precision of a real kind
PRESENT — Determine whether an optional dummy argument is specified
PRODUCT — Product of array elements
RADIX — Base of a model number
RAN — Real pseudo-random number
RAND — Real pseudo-random number
RANDOM_NUMBER — Pseudo-random number
RANDOM_SEED — Initialize a pseudo-random number sequence
RANGE — Decimal exponent range
RANK — Rank of a data object
REAL — Convert to real type
RENAME — Rename a file
REPEAT — Repeated string concatenation
RESHAPE — Function to reshape an array
RRSPACING — Reciprocal of the relative spacing
RSHIFT — Right shift bits
SAME_TYPE_AS — Query dynamic types for equality
SCALE — Scale a real value
SCAN — Scan a string for the presence of a set of characters
SECNDS — Time function
SECOND — CPU time function
SELECTED_CHAR_KIND — Choose character kind
SELECTED_INT_KIND — Choose integer kind
SELECTED_REAL_KIND — Choose real kind
SET_EXPONENT — Set the exponent of the model
SHAPE — Determine the shape of an array
SHIFTA — Right shift with fill
SHIFTL — Left shift
SHIFTR — Right shift
SIGN — Sign copying function
SIGNAL — Signal handling subroutine (or function)
SIN — Sine function
SINH — Hyperbolic sine function
SIZE — Determine the size of an array
SIZEOF — Size in bytes of an expression
SLEEP — Sleep for the specified number of seconds
SPACING — Smallest distance between two numbers of a given type
SPREAD — Add a dimension to an array
SQRT — Square-root function
SRAND — Reinitialize the random number generator
STAT — Get file status
STORAGE_SIZE — Storage size in bits
SUM — Sum of array elements
SYMLNK — Create a symbolic link
SYSTEM — Execute a shell command
SYSTEM_CLOCK — Time function
TAN — Tangent function
TANH — Hyperbolic tangent function
THIS_IMAGE — Function that returns the cosubscript index of this image
TIME — Time function
TIME8 — Time function (64-bit)
TINY — Smallest positive number of a real kind
TRAILZ — Number of trailing zero bits of an integer
TRANSFER — Transfer bit patterns
TRANSPOSE — Transpose an array of rank two
TRIM — Remove trailing blank characters of a string
TTYNAM — Get the name of a terminal device.
UBOUND — Upper dimension bounds of an array
UCOBOUND — Upper codimension bounds of an array
UMASK — Set the file creation mask
UNLINK — Remove a file from the file system
UNPACK — Unpack an array of rank one into an array
VERIFY — Scan a string for characters not a given set
XOR — Bitwise logical exclusive OR
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.
Part I: Invoking GNU Fortran
Part II: Language Reference
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 will use to invoke the compiler.
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:
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.
The GNU Fortran compiler consists of several components:
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 Introduction. The two manuals together provide a complete reference for the GNU Fortran compiler.
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 Overview 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://www.daniellnagle.com/coco.html).
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.
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, including 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, and produces acceptable results on the LAPACK Test Suite. It also provides respectable performance on the Polyhedron Fortran compiler benchmarks and the Livermore Fortran Kernels test. It has been used to compile a number of large real-world programs, including the HIRLAM weather-forecasting code and the Tonto quantum chemistry package; 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.
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.
GNU Fortran also have a partial support for ISO/IEC 1539-1:2004 (Fortran
2003), ISO/IEC 1539-1:2010 (Fortran 2008), the Technical Specification
Further Interoperability of Fortran with C (ISO/IEC TS 29113:2012).
Full support of those standards and future Fortran standards is planned.
The current status of the support is can be found in the
Fortran 2003 status, Fortran 2008 status and
TS 29113 status sections of the documentation.
Additionally, the GNU Fortran compilers supports the OpenMP specification (version 4.0, http://openmp.org/wp/openmp-specifications/).
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/.
Deferred-length character strings of Fortran 2003 supports part of
the features of ISO_VARYING_STRING and should be considered as
replacement. (Namely, allocatable or pointers of the type
character(len=:).)
The gfortran command supports all the options supported by the gcc command. Only options specific to GNU Fortran are documented here.
See GCC Command Options, 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.
Here is a summary of all the options specific to GNU Fortran, grouped by type. Explanations are in the following sections.
-fall-intrinsics -fbackslash -fcray-pointer -fd-lines-as-code
-fd-lines-as-comments -fdefault-double-8 -fdefault-integer-8
-fdefault-real-8 -fdollar-ok -ffixed-line-length-n
-ffixed-line-length-none -ffree-form -ffree-line-length-n
-ffree-line-length-none -fimplicit-none -finteger-4-integer-8
-fmax-identifier-length -fmodule-private -fno-fixed-form -fno-range-check
-fopenmp -freal-4-real-10 -freal-4-real-16 -freal-4-real-8
-freal-8-real-10 -freal-8-real-16 -freal-8-real-4 -std=std
-A-question[=answer] -Aquestion=answer -C -CC -Dmacro[=defn] -H -P -Umacro -cpp -dD -dI -dM -dN -dU -fworking-directory -imultilib dir -iprefix file -iquote -isysroot dir -isystem dir -nocpp -nostdinc -undef
-Waliasing -Wall -Wampersand -Warray-bounds
-Wc-binding-type -Wcharacter-truncation
-Wconversion -Wfunction-elimination -Wimplicit-interface
-Wimplicit-procedure -Wintrinsic-shadow -Wintrinsics-std
-Wline-truncation -Wno-align-commons -Wno-tabs -Wreal-q-constant
-Wsurprising -Wunderflow -Wunused-parameter -Wrealloc-lhs -Wrealloc-lhs-all
-Wtarget-lifetime -fmax-errors=n -fsyntax-only -pedantic -pedantic-errors
-fbacktrace -fdump-fortran-optimized -fdump-fortran-original
-fdump-parse-tree -ffpe-trap=list -ffpe-summary=list
-Idir -Jdir -fintrinsic-modules-path dir
-static-libgfortran
-fconvert=conversion -fmax-subrecord-length=length
-frecord-marker=length -fsign-zero
-faggressive-function-elimination -fblas-matmul-limit=n
-fbounds-check -fcheck-array-temporaries
-fcheck=<all|array-temps|bounds|do|mem|pointer|recursion>
-fcoarray=<none|single|lib> -fexternal-blas -ff2c
-ffrontend-optimize
-finit-character=n -finit-integer=n -finit-local-zero
-finit-logical=<true|false>
-finit-real=<zero|inf|-inf|nan|snan>
-fmax-array-constructor=n -fmax-stack-var-size=n
-fno-align-commons
-fno-automatic -fno-protect-parens -fno-underscoring
-fsecond-underscore -fpack-derived -frealloc-lhs -frecursive
-frepack-arrays -fshort-enums -fstack-arrays
The following options control the details of the Fortran dialect accepted by the compiler:
-ffree-form-ffixed-form-fall-intrinsicsEXTERNAL.
-fd-lines-as-code-fd-lines-as-commentsd 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.
-fdollar-okIMPLICIT statements is also rejected.
-fbackslash\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, \xnn, \unnnn and
\Unnnnnnnn (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-privatePRIVATE.
Use-associated entities will not be accessible unless they are explicitly
declared as PUBLIC.
-ffixed-line-length-nPopular 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-fmax-identifier-length=n-fimplicit-noneIMPLICIT statements. This is the equivalent of adding
implicit none to the start of every procedure.
-fcray-pointer-fopenmp!$omp directives
in free form
and c$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-checka = 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.
-fdefault-integer-842. Unlike
-finteger-4-integer-8, it does not promote variables with explicit
kind declaration.
-fdefault-real-81.0, and does promote
the default width of DOUBLE PRECISION to 16 bytes if possible, unless
-fdefault-double-8 is given, too. Unlike -freal-4-real-8,
it does not promote variables with explicit kind declaration.
-fdefault-double-8DOUBLE PRECISION type to an 8 byte wide type. Do nothing if this
is already the default. 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.
-finteger-4-integer-8INTEGER(KIND=4) entities to an INTEGER(KIND=8)
entities. If KIND=8 is unavailable, then an error will be issued.
This option should be used with care and may not be suitable for your codes.
Areas of possible concern include calls to external procedures,
alignment in EQUIVALENCE and/or COMMON, generic interfaces,
BOZ literal constant conversion, and I/O. Inspection of the intermediate
representation of the translated Fortran code, produced by
-fdump-tree-original, is suggested.
-freal-4-real-8-freal-4-real-10-freal-4-real-16-freal-8-real-4-freal-8-real-10-freal-8-real-16REAL(KIND=M) entities to REAL(KIND=N) entities.
If REAL(KIND=N) is unavailable, then an error will be issued.
All other real kind types are unaffected by this option.
These options should be used with care and may not be suitable for your
codes. Areas of possible concern include calls to external procedures,
alignment in EQUIVALENCE and/or COMMON, generic interfaces,
BOZ literal constant conversion, and I/O. Inspection of the intermediate
representation of the translated Fortran code, produced by
-fdump-tree-original, is suggested.
-std=stdPreprocessor related options. See section Preprocessing and conditional compilation for more detailed information on preprocessing in gfortran.
-cpp-nocppTo disable preprocessing of files with any of the above listed extensions, use the negative form: -nocpp.
The preprocessor is run in traditional mode. Any restrictions of the
file-format, especially the limits on line length, apply for
preprocessed output as well, so it might be advisable to use the
-ffree-line-length-none or -ffixed-line-length-none
options.
-dM'#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 -E -dM foo.f90
will show all the predefined macros.
-dD#define directives
and the result of preprocessing. Both kinds of output go to the
standard output file.
-dN-dU'#undef'
directives are also output for macros tested but undefined at the time.
-dI'#include' directives in addition to the result
of preprocessing.
-fworking-directory#line
directives are emitted whatsoever.
-idirafter dir=, then the = will be replaced by
the sysroot prefix; see --sysroot and -isysroot.
-imultilib dir-iprefix prefix'/'.
-isysroot dir-iquote dir#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=, then the = will be replaced by the sysroot prefix;
see --sysroot and -isysroot.
-nostdinc-undef-Apredicate=answer-A-predicate=answer-CYou 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.
-CCIn 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.
-Dname1.
-Dname=definition'#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'#include'
stack it is.
-P-UnameErrors 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-fsyntax-only-pedantic#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-Wall-WaliasingINTENT(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-Warray-temporaries-Wc-binding-typeISO_C_Binding module. This option is implied by
-Wall.
-Wcharacter-truncation-Wline-truncation-Wconversion-Wconversion-extra-Wextra-Wimplicit-interface-Wimplicit-procedureEXTERNAL.
-Wintrinsics-stdEXTERNAL 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.
-Wreal-q-constantq
exponent-letter.
-WsurprisingThis currently produces a warning under the following circumstances:
CHARACTER variable is declared with negative length.
-Wtabs-Wunderflow-Wintrinsic-shadowEXTERNAL or
INTRINSIC declaration might be needed to get calls later resolved to
the desired intrinsic/procedure. This option is implied by -Wall.
-Wunused-dummy-argument-Wunused-parameterPARAMETER values. -Wunused-parameter
is not included in -Wall but is implied by -Wall -Wextra.
-Walign-commonsCOMMON block. This warning can be turned
off via -Wno-align-commons. See also -falign-commons.
-Wfunction-elimination-Wrealloc-lhs(:,:,:)) for the variable on the left-hand
side to prevent the reallocation check. Note that in some cases the warning
is shown, even if the compiler will optimize reallocation checks away. For
instance, when the right-hand side contains the same variable multiplied by
a scalar. See also -frealloc-lhs.
-Wrealloc-lhs-all-Wcompare-reals-Wtarget-lifetime-WzerotripDO loop is known to execute zero times at compile
time. This option is implied by -Wall.
-WerrorSee Options to Request or Suppress Errors and Warnings, 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.
GNU Fortran has various special options that are used for debugging either your program or the GNU Fortran compiler.
-fdump-fortran-original-fdump-fortran-optimized-fdump-parse-tree-fdump-fortran-original instead.
-ffpe-trap=listSQRT(-1.0)), ‘zero’ (division by zero), ‘overflow’
(overflow in a floating point operation), ‘underflow’ (underflow
in a floating point operation), ‘inexact’ (loss of precision
during operation), and ‘denormal’ (operation performed on a
denormal value). The first five exceptions correspond to the five
IEEE 754 exceptions, whereas the last one (‘denormal’) is not
part of the IEEE 754 standard but is available on some common
architectures such as x86.
The first three exceptions (‘invalid’, ‘zero’, and ‘overflow’) often indicate serious errors, and unless the program has provisions for dealing with these exceptions, enabling traps for these three exceptions is probably a good idea.
Many, if not most, floating point operations incur loss of precision
due to rounding, and hence the ffpe-trap=inexact is likely to
be uninteresting in practice.
By default no exception traps are enabled.
-ffpe-summary=listERROR_UNIT when invoking STOP and ERROR STOP.
list can be either ‘none’, ‘all’ or a comma-separated list
of the following exceptions: ‘invalid’, ‘zero’, ‘overflow’,
‘underflow’, ‘inexact’ and ‘denormal’. (See
-ffpe-trap for a description of the exceptions.)
By default, a summary for all exceptions but ‘inexact’ is shown.
-fno-backtrace-fno-backtrace disables the backtrace
generation. This option only has influence for compilation of the
Fortran main program.
See Options for Debugging Your Program or GCC, for more information on debugging options.
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.
-IdirINCLUDE 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.
See Options for Directory Search, for information on the
-I option.
-JdirUSE
statement.
The default is the current directory.
-fintrinsic-modules-path dirThese 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-libgfortranThese options affect the runtime behavior of programs compiled with GNU Fortran.
-fconvert=conversionThis 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.
-frecord-marker=length-fmax-subrecord-length=length-fsign-zeroSIGN intrinsic. -fno-sign-zero does not
print the negative sign of zero values (or values rounded to zero for I/O)
and regards zero as positive number in the SIGN intrinsic for
compatibility with Fortran 77. The default is -fsign-zero.
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-automaticSAVE 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.
-ff2cThe 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-underscoringWith -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-à-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.
-fsecond-underscoreThis 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.
-fcoarray=<keyword>num_images() is always one.
-fcheck=<keyword>Note: The warning is only printed once per location.
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.
ALLOCATE statement, which will be always checked.
-fbounds-check-fcheck-array-temporaries-fmax-array-constructor=n 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=nThis 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.
-fstack-arrays-fpack-derived-frepack-arraysThis 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-enumsINTEGER kind a given
enumerator set will fit in, and give all its enumerators this kind.
-fexternal-blasMATMUL, 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=nThe default value for n is 30.
-frecursive-finit-local-zero-finit-integer=n-finit-real=<zero|inf|-inf|nan|snan>-finit-logical=<true|false>-finit-character=nINTEGER, 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
EQUIVALENCE statement.
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).
Finally, note that enabling any of the -finit-* options will
silence warnings that would have been emitted by -Wuninitialized
for the affected local variables.
-falign-commonsCOMMON 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 largest to smallest.
-fno-protect-parensREAL 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. The parentheses protection is enabled by default, unless
-Ofast is given.
-frealloc-lhs-faggressive-function-eliminationPURE or not. For example, in
a = f(b,c) + f(b,c)
there will only be a single call to f. This option only works
if -ffrontend-optimize is in effect.
-ffrontend-optimizeTRIM in comparisons and assignments and replacing
TRIM(a) with a(1:LEN_TRIM(a)).
It can be deselected by specifying -fno-frontend-optimize.
See Options for Code Generation Conventions, for information on more options offered by the GBE shared by gfortran, gcc, and other GNU compilers.
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.
See Environment Variables Affecting GCC, for information on environment variables.
See Runtime, for environment variables that affect the run-time behavior of programs compiled with GNU Fortran.
The behavior of the gfortran can be influenced by environment variables.
Malformed environment variables are silently ignored.
When opening a file with STATUS='SCRATCH', GNU Fortran tries to
create the file in one of the potential directories by testing each
directory in the order below.
GetTempPath
function. Alternatively, on the Cygwin target, the TMP and
TEMP environment variables, if they exist, in that order.
P_tmpdir macro if it is defined, otherwise the directory
/tmp.
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.
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.
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.
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.
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.
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’, do not print filename and line numbers for runtime errors. The default is to print the location.
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.
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).
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.
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.
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.
See CONVERT specifier, for an alternative way to specify the
data representation for unformatted files. See 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.
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 serious run-time error occurs. To disable the backtracing, set the variable to ‘n’, ‘N’, ‘0’. Default is to print a backtrace unless the -fno-backtrace compile option was used.
GNU Fortran supports several Fortran 2003 features; an incomplete list can be found below. See also the wiki page about Fortran 2003.
PASS attribute.
PASS, PROCEDURE and GENERIC, and
operators bound to a type.
CLASS”) for derived types and unlimited
polymorphism (“CLASS(*)”) – including SAME_TYPE_AS,
EXTENDS_TYPE_OF and SELECT TYPE for scalars and arrays and
finalization.
ASSOCIATE construct.
ALLOCATE statement, allowing for a
type-specification with type parameter and for allocation and initialization
from a SOURCE= expression; ALLOCATE and DEALLOCATE
optionally return an error message string via ERRMSG=.
MOVE_ALLOC.
PRIVATE and PUBLIC attributes may be given individually
to derived-type components.
INTENT may be specified which affect the
association status not the value of the pointer target.
command_argument_count, get_command,
get_command_argument, and get_environment_variable.
SELECTED_CHAR_KIND and NEW_LINE intrinsic functions.
INT, REAL, CMPLX and DBLE.
[...] rather
than (/.../). Type-specification for array constructors like
(/ some-type :: ... /).
FLUSH statement.
IOMSG= specifier for I/O statements.
ENUM and ENUMERATOR statements. Interoperability with
gcc is guaranteed also for the case where the
-fshort-enums command line option is given.
OPEN statement supports the ACCESS='STREAM' specifier,
allowing I/O without any record structure.
strtod honours
the rounding mode, the rounding mode is also supported for input.
PROTECTED statement and attribute.
VALUE statement and attribute.
VOLATILE statement and attribute.
IMPORT statement, allowing to import
host-associated derived types.
ISO_FORTRAN_ENVIRONMENT is supported,
which contains parameters of the I/O units, storage sizes. Additionally,
procedures for C interoperability are available in the ISO_C_BINDING
module.
USE statement with INTRINSIC and NON_INTRINSIC
attribute; supported intrinsic modules: ISO_FORTRAN_ENV,
ISO_C_BINDING, OMP_LIB and OMP_LIB_KINDS.
USE statement.
The latest version of the Fortran standard is ISO/IEC 1539-1:2010, informally known as Fortran 2008. The official version is available from International Organization for Standardization (ISO) or its national member organizations. The the final draft (FDIS) can be downloaded free of charge from http://www.nag.co.uk/sc22wg5/links.html. Fortran is developed by the Working Group 5 of Sub-Committee 22 of the Joint Technical Committee 1 of the International Organization for Standardization and the International Electrotechnical Commission (IEC). This group is known as WG5.
The GNU Fortran compiler supports several of the new features of Fortran 2008; the wiki has some information about the current Fortran 2008 implementation status. In particular, the following is implemented.
OPEN statement now supports the NEWUNIT= option,
which returns a unique file unit, thus preventing inadvertent use of the
same unit in different parts of the program.
g0 format descriptor and unlimited format items.
ASINH, ACOSH, ATANH,
ERF, ERFC, GAMMA, LOG_GAMMA, BESSEL_J0,
BESSEL_J1, BESSEL_JN, BESSEL_Y0, BESSEL_Y1,
BESSEL_YN, HYPOT, NORM2, and ERFC_SCALED.
TAN, SINH, COSH,
TANH, ASIN, ACOS, and ATAN is now possible;
ATAN(Y,X) is now an alias for ATAN2(Y,X).
PARITY intrinsic functions.
LEADZ and TRAILZ for
counting the number of leading and trailing zero bits, POPCNT and
POPPAR for counting the number of one bits and returning the parity;
BGE, BGT, BLE, and BLT for bitwise comparisons;
DSHIFTL and DSHIFTR for combined left and right shifts,
MASKL and MASKR for simple left and right justified masks,
MERGE_BITS for a bitwise merge using a mask, SHIFTA,
SHIFTL and SHIFTR for shift operations, and the
transformational bit intrinsics IALL, IANY and IPARITY.
EXECUTE_COMMAND_LINE intrinsic subroutine.
STORAGE_SIZE intrinsic inquiry function.
INT{8,16,32} and REAL{32,64,128} kind type
parameters and the array-valued named constants INTEGER_KINDS,
LOGICAL_KINDS, REAL_KINDS and CHARACTER_KINDS of
the intrinsic module ISO_FORTRAN_ENV.
C_SIZEOF of the intrinsic module
ISO_C_BINDINGS and COMPILER_VERSION and COMPILER_OPTIONS
of ISO_FORTRAN_ENV.
DO CONCURRENT construct is supported.
BLOCK construct is supported.
STOP and the new ERROR STOP statements now
support all constant expressions. Both show the signals which were signaling
at termination.
CONTIGUOUS attribute.
ALLOCATE with MOLD.
IMPURE attribute for procedures, which
allows for ELEMENTAL procedures without the restrictions of
PURE.
NULL()) and not-allocated variables
can be used as actual argument to optional non-pointer, non-allocatable
dummy arguments, denoting an absent argument.
TARGET attribute can be used as
actual argument to POINTER dummies with INTENT(IN).
NULL.
EXIT statement (with construct-name) can be now be
used to leave not only the DO but also the ASSOCIATE,
BLOCK, IF, SELECT CASE and SELECT TYPE
constructs.
ENTRY with
-std=f2008; a line may start with a semicolon; for internal
and module procedures END can be used instead of
END SUBROUTINE and END FUNCTION; SELECTED_REAL_KIND
now also takes a RADIX argument; intrinsic types are supported
for TYPE(intrinsic-type-spec); multiple type-bound procedures
can be declared in a single PROCEDURE statement; implied-shape
arrays are supported for named constants (PARAMETER).
GNU Fortran supports some of the new features of the Technical Specification (TS) 29113 on Further Interoperability of Fortran with C. The wiki has some information about the current TS 29113 implementation status. In particular, the following is implemented.
See also Further Interoperability of Fortran with C.
OPTIONAL attribute is allowed for dummy arguments
of BIND(C) procedures.
RANK intrinsic is supported.
ASYNCHRONOUS
attribute is compatible with TS 29113.
TYPE(*).
DIMENSION(..)). However, the array descriptor
of the TS is not yet supported.
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.
The KIND type parameters supported by GNU Fortran for the primitive
data types are:
INTEGERLOGICALREALCOMPLEXDOUBLE PRECISIONCHARACTER* not available on all systems
** unless -fdefault-integer-8 is used
*** unless -fdefault-real-8 is used (see Fortran Dialect Options)
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 SELECTED_CHAR_KIND, SELECTED_INT_KIND and
SELECTED_REAL_KIND intrinsics or the INT8, INT16,
INT32, INT64, REAL32, REAL64, and REAL128
parameters of the ISO_FORTRAN_ENV module instead of the concrete values.
The available kind parameters can be found in the constant arrays
CHARACTER_KINDS, INTEGER_KINDS, LOGICAL_KINDS and
REAL_KINDS in the ISO_FORTRAN_ENV module. For C interoperability,
the kind parameters of the ISO_C_BINDING module should be used.
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.
See also Argument passing conventions and Interoperability with C.
GNU Fortran can be used in programs with multiple threads, e.g. by
using OpenMP, by calling OS thread handling functions via the
ISO_C_BINDING facility, or by GNU Fortran compiled library code
being called from a multi-threaded program.
The GNU Fortran runtime library, (libgfortran), supports being
called concurrently from multiple threads with the following
exceptions.
During library initialization, the C getenv function is used,
which need not be thread-safe. Similarly, the getenv
function is used to implement the GET_ENVIRONMENT_VARIABLE and
GETENV intrinsics. It is the responsibility of the user to
ensure that the environment is not being updated concurrently when any
of these actions are taking place.
The EXECUTE_COMMAND_LINE and SYSTEM intrinsics are
implemented with the system function, which need not be
thread-safe. It is the responsibility of the user to ensure that
system is not called concurrently.
Finally, for platforms not supporting thread-safe POSIX functions, further functionality might not be thread-safe. For details, please consult the documentation for your operating system.
This section contains a brief overview of data and metadata consistency and durability issues when doing I/O.
With respect to durability, GNU Fortran makes no effort to ensure that
data is committed to stable storage. If this is required, the GNU
Fortran programmer can use the intrinsic FNUM to retrieve the
low level file descriptor corresponding to an open Fortran unit. Then,
using e.g. the ISO_C_BINDING feature, one can call the
underlying system call to flush dirty data to stable storage, such as
fsync on POSIX, _commit on MingW, or fcntl(fd,
F_FULLSYNC, 0) on Mac OS X. The following example shows how to call
fsync:
! Declare the interface for POSIX fsync function
interface
function fsync (fd) bind(c,name="fsync")
use iso_c_binding, only: c_int
integer(c_int), value :: fd
integer(c_int) :: fsync
end function fsync
end interface
! Variable declaration
integer :: ret
! Opening unit 10
open (10,file="foo")
! ...
! Perform I/O on unit 10
! ...
! Flush and sync
flush(10)
ret = fsync(fnum(10))
! Handle possible error
if (ret /= 0) stop "Error calling FSYNC"
With respect to consistency, for regular files GNU Fortran uses
buffered I/O in order to improve performance. This buffer is flushed
automatically when full and in some other situations, e.g. when
closing a unit. It can also be explicitly flushed with the
FLUSH statement. Also, the buffering can be turned off with the
GFORTRAN_UNBUFFERED_ALL and
GFORTRAN_UNBUFFERED_PRECONNECTED environment variables. Special
files, such as terminals and pipes, are always unbuffered. Sometimes,
however, further things may need to be done in order to allow other
processes to see data that GNU Fortran has written, as follows.
The Windows platform supports a relaxed metadata consistency model,
where file metadata is written to the directory lazily. This means
that, for instance, the dir command can show a stale size for a
file. One can force a directory metadata update by closing the unit,
or by calling _commit on the file descriptor. Note, though,
that _commit will force all dirty data to stable storage, which
is often a very slow operation.
The Network File System (NFS) implements a relaxed consistency model
called open-to-close consistency. Closing a file forces dirty data and
metadata to be flushed to the server, and opening a file forces the
client to contact the server in order to revalidate cached
data. fsync will also force a flush of dirty data and metadata
to the server. Similar to open and close, acquiring and
releasing fcntl file locks, if the server supports them, will
also force cache validation and flushing dirty data and metadata.
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.
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.
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
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.
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
/
When writing a namelist, if no DELIM= is specified, by default a
double quote is used to delimit character strings. If -std=F95, F2003,
or F2008, etc, the delim status is set to 'none'. Defaulting to
quotes ensures that namelists with character strings can be subsequently
read back in accurately.
X format descriptor without count fieldTo 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)
FORMAT specificationsTo 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)
FORMAT specificationsTo 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')
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.
Q exponent-letter
GNU Fortran accepts real literal constants with an exponent-letter
of Q, for example, 1.23Q45. The constant is interpreted
as a REAL(16) entity on targets that support this type. If
the target does not support REAL(16) but has a REAL(10)
type, then the real-literal-constant will be interpreted as a
REAL(10) entity. In the absence of REAL(16) and
REAL(10), an error will occur.
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.
As an extension, GNU Fortran allows the use of REAL expressions
or variables as array indices.
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
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.
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
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 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, nor
may they be function results. 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.
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.
See 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.
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 v4.0.
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 libgomp.
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:
%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.
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.
STRUCTURE and RECORDRecord structures are a pre-Fortran-90 vendor extension to create user-defined aggregate data types. GNU Fortran does not support record structures, only Fortran 90's “derived types”, which have a different syntax.
In many cases, record structures can easily be converted to derived types.
To convert, replace STRUCTURE /structure-name/
by TYPE type-name. Additionally, replace
RECORD /structure-name/ by
TYPE(type-name). Finally, in the component access,
replace the period (.) by the percent sign (%).
Here is an example of code using the non portable record 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 do not change
store_catalog(12) = pear
print *, store_catalog(12)
ENCODE and DECODE statements
GNU Fortran does not 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))
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) FMT
c
c Other code here...
c
WRITE(FMT,'("(I", I0, ")")') N+1
WRITE(6,FMT) 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
Some Fortran compilers, including g77, let the user declare
complex functions with the syntax COMPLEX FUNCTION name*16(), as
well as COMPLEX*16 FUNCTION name(). Both are non-standard, legacy
extensions. gfortran accepts the latter form, which is more
common, but not the former.
COMMON blocks
Some Fortran compilers, including g77, let the user declare
COMMON with the VOLATILE attribute. This is
invalid standard Fortran syntax and is not supported by
gfortran. Note that gfortran accepts
VOLATILE variables in COMMON blocks since revision 4.3.
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.
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]).
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 ISO_C_BINDING.
For logical types, please note that the Fortran standard only guarantees
interoperability between C99's _Bool and Fortran's C_Bool-kind
logicals and C99 defines that true has the value 1 and false
the value 0. Using any other integer value with GNU Fortran's LOGICAL
(with any kind parameter) gives an undefined result. (Passing other integer
values than 0 and 1 to GCC's _Bool is also undefined, unless the
integer is explicitly or implicitly casted to _Bool.)
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
components 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.
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.
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 in Fortran 2003 and 2008 only explicit size
and assumed-size arrays are supported but not assumed-shape or
deferred-shape (i.e. allocatable or pointer) arrays. However, those
are allowed since the Technical Specification 29113, see
Further Interoperability of Fortran with C
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,
see Working with Pointers.
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 strings is now further 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
The intrinsic procedures are described in Intrinsic Procedures.
C pointers are represented in Fortran via the special opaque derived type
type(c_ptr) (with private components). Thus one needs to
use intrinsic conversion procedures to convert from or to C pointers.
For some applications, using an assumed type (TYPE(*)) can be an
alternative to a C pointer; see
Further Interoperability of Fortran with C.
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.
If a pointer is a dummy-argument of an interoperable procedure, it usually
has to be declared using the VALUE attribute. void*
matches TYPE(C_PTR), VALUE, while TYPE(C_PTR) alone
matches void**.
Procedure pointers are handled analogously to pointers; the C type is
TYPE(C_FUNPTR) and the intrinsic conversion procedures are
C_F_PROCPOINTER and C_FUNLOC.
Let us consider two examples of actually passing a procedure pointer from C to Fortran and vice versa. Note that these examples are also very similar to passing ordinary pointers between both languages. First, consider this code in C:
/* Procedure implemented in Fortran. */
void get_values (void (*)(double));
/* Call-back routine we want called from Fortran. */
void
print_it (double x)
{
printf ("Number is %f.\n", x);
}
/* Call Fortran routine and pass call-back to it. */
void
foobar ()
{
get_values (&print_it);
}
A matching implementation for get_values in Fortran, that correctly
receives the procedure pointer from C and is able to call it, is given
in the following MODULE:
MODULE m
IMPLICIT NONE
! Define interface of call-back routine.
ABSTRACT INTERFACE
SUBROUTINE callback (x)
USE, INTRINSIC :: ISO_C_BINDING
REAL(KIND=C_DOUBLE), INTENT(IN), VALUE :: x
END SUBROUTINE callback
END INTERFACE
CONTAINS
! Define C-bound procedure.
SUBROUTINE get_values (cproc) BIND(C)
USE, INTRINSIC :: ISO_C_BINDING
TYPE(C_FUNPTR), INTENT(IN), VALUE :: cproc
PROCEDURE(callback), POINTER :: proc
! Convert C to Fortran procedure pointer.
CALL C_F_PROCPOINTER (cproc, proc)
! Call it.
CALL proc (1.0_C_DOUBLE)
CALL proc (-42.0_C_DOUBLE)
CALL proc (18.12_C_DOUBLE)
END SUBROUTINE get_values
END MODULE m
Next, we want to call a C routine that expects a procedure pointer argument and pass it a Fortran procedure (which clearly must be interoperable!). Again, the C function may be:
int
call_it (int (*func)(int), int arg)
{
return func (arg);
}
It can be used as in the following Fortran code:
MODULE m
USE, INTRINSIC :: ISO_C_BINDING
IMPLICIT NONE
! Define interface of C function.
INTERFACE
INTEGER(KIND=C_INT) FUNCTION call_it (func, arg) BIND(C)
USE, INTRINSIC :: ISO_C_BINDING
TYPE(C_FUNPTR), INTENT(IN), VALUE :: func
INTEGER(KIND=C_INT), INTENT(IN), VALUE :: arg
END FUNCTION call_it
END INTERFACE
CONTAINS
! Define procedure passed to C function.
! It must be interoperable!
INTEGER(KIND=C_INT) FUNCTION double_it (arg) BIND(C)
INTEGER(KIND=C_INT), INTENT(IN), VALUE :: arg
double_it = arg + arg
END FUNCTION double_it
! Call C function.
SUBROUTINE foobar ()
TYPE(C_FUNPTR) :: cproc
INTEGER(KIND=C_INT) :: i
! Get C procedure pointer.
cproc = C_FUNLOC (double_it)
! Use it.
DO i = 1_C_INT, 10_C_INT
PRINT *, call_it (cproc, i)
END DO
END SUBROUTINE foobar
END MODULE m
The Technical Specification ISO/IEC TS 29113:2012 on further
interoperability of Fortran with C extends the interoperability support
of Fortran 2003 and Fortran 2008. Besides removing some restrictions
and constraints, it adds assumed-type (TYPE(*)) and assumed-rank
(dimension) variables and allows for interoperability of
assumed-shape, assumed-rank and deferred-shape arrays, including
allocatables and pointers.
Note: Currently, GNU Fortran does not support the array descriptor (dope vector) as specified in the Technical Specification, but uses an array descriptor with different fields. The Chasm Language Interoperability Tools, http://chasm-interop.sourceforge.net/, provide an interface to GNU Fortran's array descriptor.
The Technical Specification adds the following new features, which are supported by GNU Fortran:
ASYNCHRONOUS attribute has been clarified and
extended to allow its use with asynchronous communication in
user-provided libraries such as in implementations of the
Message Passing Interface specification.
C_LOC and C_F_POINTER intrinsics.
OPTIONAL attribute is now allowed for dummy
arguments; an absent argument matches a NULL pointer.
TYPE(*)) have been added, which may
only be used for dummy arguments. They are unlimited polymorphic
but contrary to CLASS(*) they do not contain any type
information, similar to C's void * pointers. Expressions
of any type and kind can be passed; thus, it can be used as
replacement for TYPE(C_PTR), avoiding the use of
C_LOC in the caller.
Note, however, that TYPE(*) only accepts scalar arguments,
unless the DIMENSION is explicitly specified. As
DIMENSION(*) only supports array (including array elements) but
no scalars, it is not a full replacement for C_LOC. On the
other hand, assumed-type assumed-rank dummy arguments
(TYPE(*), DIMENSION(..)) allow for both scalars and arrays, but
require special code on the callee side to handle the array descriptor.
DIMENSION(..)) as dummy argument
allow that scalars and arrays of any rank can be passed as actual
argument. As the Technical Specification does not provide for direct
means to operate with them, they have to be used either from the C side
or be converted using C_LOC and C_F_POINTER to scalars
or arrays of a specific rank. The rank can be determined using the
RANK intrinisic.
Currently unimplemented:
ISO_Fortran_binding.h header file and the C functions it
specifies are not available.
BIND(C) procedures is not fully supported. In particular,
C interoperable strings of other length than one are not supported
as this requires the new array descriptor.
The Fortran 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 C Extensions 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
For dummy arguments, the NO_ARG_CHECK attribute can be used; in
other compilers, it is also known as IGNORE_TKR. For dummy arguments
with this attribute actual arguments of any type and kind (similar to
TYPE(*)), scalars and arrays of any rank (no equivalent
in Fortran standard) are accepted. As with TYPE(*), the argument
is unlimited polymorphic and no type information is available.
Additionally, the argument may only be passed to dummy arguments
with the NO_ARG_CHECK attribute and as argument to the
PRESENT intrinsic function and to C_LOC of the
ISO_C_BINDING module.
Variables with NO_ARG_CHECK attribute shall be of assumed-type
(TYPE(*); recommended) or of type INTEGER, LOGICAL,
REAL or COMPLEX. They shall not have the ALLOCATE,
CODIMENSION, INTENT(OUT), POINTER or VALUE
attribute; furthermore, they shall be either scalar or of assumed-size
(dimension(*)). As TYPE(*), the NO_ARG_CHECK attribute
requires an explicit interface.
NO_ARG_CHECK – disable the type, kind and rank checking
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.
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.
_gfortran_set_args — Save command-line arguments_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).
void _gfortran_set_args (int argc, char *argv[])
| argc | number of command line argument strings
|
| argv | the command-line argument strings; argv[0]
is the pathname of the executable itself.
|
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
return 0;
}
_gfortran_set_options — Set library option flags_gfortran_set_options sets several flags related to the Fortran
standard to be used, whether backtracing 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
see Code Gen Options. Please note that not all flags are actually
used.
void _gfortran_set_options (int num, int options[])
| num | number of options passed
|
| argv | The list of flag values
|
| 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), GFC_STD_F2008 (128),
GFC_STD_F2008_OBS (256) and GFC_STD_F2008_TS (512). Default:
GFC_STD_F95_OBS | GFC_STD_F95_DEL | GFC_STD_F95 | GFC_STD_F2003
| GFC_STD_F2008 | GFC_STD_F2008_TS | GFC_STD_F2008_OBS | 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] | Unused.
|
| option[4] | If non zero, enable backtracing on run-time
errors. Default: off. (Default in the compiler: on.)
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] | Unused.
|
| option[8] | Show a warning when invoking STOP and
ERROR STOP if a floating-point exception occurred. Possible values
are (bitwise or-ed) GFC_FPE_INVALID (1), GFC_FPE_DENORMAL (2),
GFC_FPE_ZERO (4), GFC_FPE_OVERFLOW (8),
GFC_FPE_UNDERFLOW (16), GFC_FPE_INEXACT (32). Default: None (0).
(Default in the compiler: GFC_FPE_INVALID | GFC_FPE_DENORMAL |
GFC_FPE_ZERO | GFC_FPE_OVERFLOW | GFC_FPE_UNDERFLOW.)
|
/* Use gfortran 4.9 default options. */
static int options[] = {68, 511, 0, 0, 1, 1, 0, 0, 31};
_gfortran_set_options (9, &options);
_gfortran_set_convert — Set endian conversion_gfortran_set_convert set the representation of data for
unformatted files.
void _gfortran_set_convert (int conv)
| conv | Endian conversion, possible values:
GFC_CONVERT_NATIVE (0, default), GFC_CONVERT_SWAP (1),
GFC_CONVERT_BIG (2), GFC_CONVERT_LITTLE (3).
|
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_convert (1);
return 0;
}
_gfortran_set_record_marker — Set length of record markers_gfortran_set_record_marker sets the length of record markers
for unformatted files.
void _gfortran_set_record_marker (int val)
| val | Length of the record marker; valid values
are 4 and 8. Default is 4.
|
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_record_marker (8);
return 0;
}
_gfortran_set_fpe — Enable floating point exception traps_gfortran_set_fpe enables floating point exception traps for
the specified exceptions. On most systems, this will result in a
SIGFPE signal being sent and the program being aborted.
void _gfortran_set_fpe (int val)
| 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_INEXACT (32).
|
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;
}
_gfortran_set_max_subrecord_length — Set subrecord length_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.
void _gfortran_set_max_subrecord_length (int val)
| val | the maximum length for a subrecord;
the maximum permitted value is 2147483639, which is also
the default.
|
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_max_subrecord_length (8);
return 0;
}
This section gives an overview about the naming convention of procedures and global variables and about the argument passing conventions used by GNU Fortran. If a C binding has been specified, the naming convention and some of the argument-passing conventions change. If possible, mixed-language and mixed-compiler projects should use the better defined C binding for interoperability. See see Interoperability with C.
According the Fortran standard, valid Fortran names consist of a letter
between A to Z, a to z, digits 0,
1 to 9 and underscores (_) with the restriction
that names may only start with a letter. As vendor extension, the
dollar sign ($) is additionally permitted with the option
-fdollar-ok, but not as first character and only if the
target system supports it.
By default, the procedure name is the lower-cased Fortran name with an
appended underscore (_); using -fno-underscoring no
underscore is appended while -fsecond-underscore appends two
underscores. Depending on the target system and the calling convention,
the procedure might be additionally dressed; for instance, on 32bit
Windows with stdcall, an at-sign @ followed by an integer
number is appended. For the changing the calling convention, see
see GNU Fortran Compiler Directives.
For common blocks, the same convention is used, i.e. by default an
underscore is appended to the lower-cased Fortran name. Blank commons
have the name __BLNK__.
For procedures and variables declared in the specification space of a
module, the name is formed by __, followed by the lower-cased
module name, _MOD_, and the lower-cased Fortran name. Note that
no underscore is appended.
Subroutines do not return a value (matching C99's void) while
functions either return a value as specified in the platform ABI or
the result variable is passed as hidden argument to the function and
no result is returned. A hidden result variable is used when the
result variable is an array or of type CHARACTER.
Arguments are passed according to the platform ABI. In particular,
complex arguments might not be compatible to a struct with two real
components for the real and imaginary part. The argument passing
matches the one of C99's _Complex. Functions with scalar
complex result variables return their value and do not use a
by-reference argument. Note that with the -ff2c option,
the argument passing is modified and no longer completely matches
the platform ABI. Some other Fortran compilers use f2c
semantic by default; this might cause problems with
interoperablility.
GNU Fortran passes most arguments by reference, i.e. by passing a pointer to the data. Note that the compiler might use a temporary variable into which the actual argument has been copied, if required semantically (copy-in/copy-out).
For arguments with ALLOCATABLE and POINTER
attribute (including procedure pointers), a pointer to the pointer
is passed such that the pointer address can be modified in the
procedure.
For dummy arguments with the VALUE attribute: Scalar arguments
of the type INTEGER, LOGICAL, REAL and
COMPLEX are passed by value according to the platform ABI.
(As vendor extension and not recommended, using %VAL() in the
call to a procedure has the same effect.) For TYPE(C_PTR) and
procedure pointers, the pointer itself is passed such that it can be
modified without affecting the caller.
For Boolean (LOGICAL) arguments, please note that GCC expects
only the integer value 0 and 1. If a GNU Fortran LOGICAL
variable contains another integer value, the result is undefined.
As some other Fortran compilers use -1 for .TRUE.,
extra care has to be taken – such as passing the value as
INTEGER. (The same value restriction also applies to other
front ends of GCC, e.g. to GCC's C99 compiler for _Bool
or GCC's Ada compiler for Boolean.)
For arguments of CHARACTER type, the character length is passed
as hidden argument. For deferred-length strings, the value is passed
by reference, otherwise by value. The character length has the type
INTEGER(kind=4). Note with C binding, CHARACTER(len=1)
result variables are returned according to the platform ABI and no
hidden length argument is used for dummy arguments; with VALUE,
those variables are passed by value.
For OPTIONAL dummy arguments, an absent argument is denoted
by a NULL pointer, except for scalar dummy arguments of type
INTEGER, LOGICAL, REAL and COMPLEX
which have the VALUE attribute. For those, a hidden Boolean
argument (logical(kind=C_bool),value) is used to indicate
whether the argument is present.
Arguments which are assumed-shape, assumed-rank or deferred-rank
arrays or, with -fcoarray=lib, allocatable scalar coarrays use
an array descriptor. All other arrays pass the address of the
first element of the array. With -fcoarray=lib, the token
and the offset belonging to nonallocatable coarrays dummy arguments
are passed as hidden argument along the character length hidden
arguments. The token is an oparque pointer identifying the coarray
and the offset is a passed-by-value integer of kind C_PTRDIFF_T,
denoting the byte offset between the base address of the coarray and
the passed scalar or first element of the passed array.
The arguments are passed in the following order
CHARACTER and no C binding is used
CHARACTER or a nonallocatable coarray dummy
argument, followed by the hidden arguments of the next dummy argument
of such a type
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.
ABORT — Abort the programABORT causes immediate termination of the program. On operating
systems that support a core dump, ABORT will produce a core dump.
It will also print a backtrace, unless -fno-backtrace is given.
CALL ABORT
program test_abort
integer :: i = 1, j = 2
if (i /= j) call abort
end program test_abort
ABS — Absolute valueABS(A) computes the absolute value of A.
RESULT = ABS(A)
| A | The type of the argument shall be an INTEGER,
REAL, or COMPLEX.
|
REAL for a
COMPLEX argument.
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
| Name | Argument | Return type | Standard
|
ABS(A) | REAL(4) A | REAL(4) | Fortran 77 and later
|
CABS(A) | COMPLEX(4) A | REAL(4) | Fortran 77 and later
|
DABS(A) | REAL(8) A | REAL(8) | Fortran 77 and later
|
IABS(A) | INTEGER(4) A | INTEGER(4) | Fortran 77 and later
|
ZABS(A) | COMPLEX(8) A | COMPLEX(8) | GNU extension
|
CDABS(A) | COMPLEX(8) A | COMPLEX(8) | GNU extension
|
ACCESS — Checks file access modesACCESS(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.
RESULT = ACCESS(NAME, MODE)
| 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.
|
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.
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
ACHAR — Character in ASCII collating sequenceACHAR(I) returns the character located at position I
in the ASCII collating sequence.
RESULT = ACHAR(I [, KIND])
| I | The type shall be INTEGER.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
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.
program test_achar
character c
c = achar(32)
end program test_achar
ACOS — Arccosine functionACOS(X) computes the arccosine of X (inverse of COS(X)).
RESULT = ACOS(X)
| X | The type shall either be REAL with a magnitude that is
less than or equal to one - or the type shall be COMPLEX.
|
program test_acos
real(8) :: x = 0.866_8
x = acos(x)
end program test_acos
| Name | Argument | Return type | Standard
|
ACOS(X) | REAL(4) X | REAL(4) | Fortran 77 and later
|
DACOS(X) | REAL(8) X | REAL(8) | Fortran 77 and later
|
ACOSH — Inverse hyperbolic cosine functionACOSH(X) computes the inverse hyperbolic cosine of X.
RESULT = ACOSH(X)
| X | The type shall be REAL or COMPLEX.
|
PROGRAM test_acosh
REAL(8), DIMENSION(3) :: x = (/ 1.0, 2.0, 3.0 /)
WRITE (*,*) ACOSH(x)
END PROGRAM
| Name | Argument | Return type | Standard
|
DACOSH(X) | REAL(8) X | REAL(8) | GNU extension
|
ADJUSTL — Left adjust a stringADJUSTL(STRING) will left adjust a string by removing leading spaces.
Spaces are inserted at the end of the string as needed.
RESULT = ADJUSTL(STRING)
| STRING | The type shall be CHARACTER.
|
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.
program test_adjustl
character(len=20) :: str = ' gfortran'
str = adjustl(str)
print *, str
end program test_adjustl
ADJUSTR — Right adjust a stringADJUSTR(STRING) will right adjust a string by removing trailing spaces.
Spaces are inserted at the start of the string as needed.
RESULT = ADJUSTR(STRING)
| STR | The type shall be CHARACTER.
|
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.
program test_adjustr
character(len=20) :: str = 'gfortran'
str = adjustr(str)
print *, str
end program test_adjustr
AIMAG — Imaginary part of complex numberAIMAG(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.
RESULT = AIMAG(Z)
| Z | The type of the argument shall be COMPLEX.
|
REAL with the
kind type parameter of the argument.
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
| Name | Argument | Return type | Standard
|
AIMAG(Z) | COMPLEX Z | REAL | GNU extension
|
DIMAG(Z) | COMPLEX(8) Z | REAL(8) | GNU extension
|
IMAG(Z) | COMPLEX Z | REAL | GNU extension
|
IMAGPART(Z) | COMPLEX Z | REAL | GNU extension
|
AINT — Truncate to a whole numberAINT(A [, KIND]) truncates its argument to a whole number.
RESULT = AINT(A [, KIND])
| A | The type of the argument shall be REAL.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
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.
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
| Name | Argument | Return type | Standard
|
AINT(A) | REAL(4) A | REAL(4) | Fortran 77 and later
|
DINT(A) | REAL(8) A | REAL(8) | Fortran 77 and later
|
ALARM — Execute a routine after a given delayALARM(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.
CALL ALARM(SECONDS, HANDLER [, STATUS])
| 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).
|
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.
ALL — All values in MASK along DIM are trueALL(MASK [, DIM]) determines if all the values are true in MASK
in the array along dimension DIM.
RESULT = ALL(MASK [, DIM])
| 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.
|
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.
ALL(MASK) is true if all elements of MASK are true.
It also is true if MASK has zero size; otherwise, it is false.
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.
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
ALLOCATED — Status of an allocatable entityALLOCATED(ARRAY) and ALLOCATED(SCALAR) check the allocation
status of ARRAY and SCALAR, respectively.
SCALAR= keyword and allocatable
scalar entities are available in Fortran 2003 and later.
RESULT = ALLOCATED(ARRAY)
|
RESULT = ALLOCATED(SCALAR)
|
| ARRAY | The argument shall be an ALLOCATABLE array.
|
| SCALAR | The argument shall be an ALLOCATABLE scalar.
|
LOGICAL with the default logical
kind type parameter. If the argument is allocated, then the result is
.TRUE.; otherwise, it returns .FALSE.
program test_allocated
integer :: i = 4
real(4), allocatable :: x(:)
if (.not. allocated(x)) allocate(x(i))
end program test_allocated
AND — Bitwise logical ANDAND.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. For integer arguments, programmers should consider
the use of the IAND intrinsic defined by the Fortran standard.
RESULT = AND(I, J)
| 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.
|
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.
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
ANINT — Nearest whole numberANINT(A [, KIND]) rounds its argument to the nearest whole number.
RESULT = ANINT(A [, KIND])
| A | The type of the argument shall be REAL.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
ANINT(A) returns AINT(X+0.5). If A is
less than or equal to zero then it returns AINT(X-0.5).
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
| Name | Argument | Return type | Standard
|
AINT(A) | REAL(4) A | REAL(4) | Fortran 77 and later
|
DNINT(A) | REAL(8) A | REAL(8) | Fortran 77 and later
|
ANY — Any value in MASK along DIM is trueANY(MASK [, DIM]) determines if any of the values in the logical array
MASK along dimension DIM are .TRUE..
RESULT = ANY(MASK [, DIM])
| 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.
|
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.
ANY(MASK) is true if any element of MASK is true;
otherwise, it is false. It also is false if MASK has zero size.
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.
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
ASIN — Arcsine functionASIN(X) computes the arcsine of its X (inverse of SIN(X)).
RESULT = ASIN(X)
| X | The type shall be either REAL and a magnitude that is
less than or equal to one - or be COMPLEX.
|
program test_asin
real(8) :: x = 0.866_8
x = asin(x)
end program test_asin
| Name | Argument | Return type | Standard
|
ASIN(X) | REAL(4) X | REAL(4) | Fortran 77 and later
|
DASIN(X) | REAL(8) X | REAL(8) | Fortran 77 and later
|
ASINH — Inverse hyperbolic sine functionASINH(X) computes the inverse hyperbolic sine of X.
RESULT = ASINH(X)
| X | The type shall be REAL or COMPLEX.
|
PROGRAM test_asinh
REAL(8), DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /)
WRITE (*,*) ASINH(x)
END PROGRAM
| Name | Argument | Return type | Standard
|
DASINH(X) | REAL(8) X | REAL(8) | GNU extension.
|
ASSOCIATED — Status of a pointer or pointer/target pairASSOCIATED(POINTER [, TARGET]) determines the status of the pointer
POINTER or if POINTER is associated with the target TARGET.
RESULT = ASSOCIATED(POINTER [, TARGET])
| 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.
|
ASSOCIATED(POINTER) returns a scalar value of type LOGICAL(4).
There are several cases:
ASSOCIATED(POINTER) is true if POINTER is associated with a target; otherwise, it returns false.
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
ATAN — Arctangent functionATAN(X) computes the arctangent of X.
RESULT = ATAN(X)
|
RESULT = ATAN(Y, X)
|
| 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.
|
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.
program test_atan
real(8) :: x = 2.866_8
x = atan(x)
end program test_atan
| Name | Argument | Return type | Standard
|
ATAN(X) | REAL(4) X | REAL(4) | Fortran 77 and later
|
DATAN(X) | REAL(8) X | REAL(8) | Fortran 77 and later
|
ATAN2 — Arctangent functionATAN2(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 Cartesian into polar coordinates and
allows to determine the angle in the correct quadrant.
RESULT = ATAN2(Y, X)
| 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.
|
program test_atan2
real(4) :: x = 1.e0_4, y = 0.5e0_4
x = atan2(y,x)
end program test_atan2
| Name | Argument | Return type | Standard
|
ATAN2(X, Y) | REAL(4) X, Y | REAL(4) | Fortran 77 and later
|
DATAN2(X, Y) | REAL(8) X, Y | REAL(8) | Fortran 77 and later
|
ATANH — Inverse hyperbolic tangent functionATANH(X) computes the inverse hyperbolic tangent of X.
RESULT = ATANH(X)
| X | The type shall be REAL or COMPLEX.
|
PROGRAM test_atanh
REAL, DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /)
WRITE (*,*) ATANH(x)
END PROGRAM
| Name | Argument | Return type | Standard
|
DATANH(X) | REAL(8) X | REAL(8) | GNU extension
|
ATOMIC_DEFINE — Setting a variable atomicallyATOMIC_DEFINE(ATOM, VALUE) defines the variable ATOM with the value
VALUE atomically.
CALL ATOMIC_DEFINE(ATOM, VALUE)
| ATOM | Scalar coarray or coindexed variable of either integer
type with ATOMIC_INT_KIND kind or logical type
with ATOMIC_LOGICAL_KIND kind.
|
| VALURE | Scalar and of the same type as ATOM. If the kind
is different, the value is converted to the kind of
ATOM.
|
program atomic
use iso_fortran_env
integer(atomic_int_kind) :: atom[*]
call atomic_define (atom[1], this_image())
end program atomic
ATOMIC_REF — Obtaining the value of a variable atomicallyATOMIC_DEFINE(ATOM, VALUE) atomically assigns the value of the
variable ATOM to VALUE.
CALL ATOMIC_REF(VALUE, ATOM)
| VALURE | Scalar and of the same type as ATOM. If the kind
is different, the value is converted to the kind of
ATOM.
|
| ATOM | Scalar coarray or coindexed variable of either integer
type with ATOMIC_INT_KIND kind or logical type
with ATOMIC_LOGICAL_KIND kind.
|
program atomic
use iso_fortran_env
logical(atomic_logical_kind) :: atom[*]
logical :: val
call atomic_ref (atom, .false.)
! ...
call atomic_ref (atom, val)
if (val) then
print *, "Obtained"
end if
end program atomic
BACKTRACE — Show a backtraceBACKTRACE shows a backtrace at an arbitrary place in user code. Program
execution continues normally afterwards. The backtrace information is printed
to the unit corresponding to ERROR_UNIT in ISO_FORTRAN_ENV.
CALL BACKTRACE
BESSEL_J0 — Bessel function of the first kind of order 0BESSEL_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.
RESULT = BESSEL_J0(X)
| X | The type shall be REAL, and it shall be scalar.
|
REAL and lies in the
range - 0.4027... \leq Bessel (0,x) \leq 1. It has the same
kind as X.
program test_besj0
real(8) :: x = 0.0_8
x = bessel_j0(x)
end program test_besj0
| Name | Argument | Return type | Standard
|
DBESJ0(X) | REAL(8) X | REAL(8) | GNU extension
|
BESSEL_J1 — Bessel function of the first kind of order 1BESSEL_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.
RESULT = BESSEL_J1(X)
| X | The type shall be REAL, and it shall be scalar.
|
REAL and it lies in the
range - 0.5818... \leq Bessel (0,x) \leq 0.5818 . It has the same
kind as X.
program test_besj1
real(8) :: x = 1.0_8
x = bessel_j1(x)
end program test_besj1
| Name | Argument | Return type | Standard
|
DBESJ1(X) | REAL(8) X | REAL(8) | GNU extension
|
BESSEL_JN — Bessel function of the first kindBESSEL_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 N and X are arrays,
their ranks and shapes shall conform.
BESSEL_JN(N1, N2, X) returns an array with the Bessel functions
of the first kind of the orders N1 to N2.
BESSEL_JN(N1, N2, X)
RESULT = BESSEL_JN(N, X)
|
RESULT = BESSEL_JN(N1, N2, X)
|
| N | Shall be a scalar or an array of type INTEGER.
|
| N1 | Shall be a non-negative scalar of type INTEGER.
|
| N2 | Shall be a non-negative scalar of type INTEGER.
|
| X | Shall be a scalar or an array of type REAL;
for BESSEL_JN(N1, N2, X) it shall be scalar.
|
REAL. It has the same
kind as X.
program test_besjn
real(8) :: x = 1.0_8
x = bessel_jn(5,x)
end program test_besjn
| Name | Argument | Return type | Standard
|
DBESJN(N, X) | INTEGER N | REAL(8) | GNU extension
|
REAL(8) X |
|
BESSEL_Y0 — Bessel function of the second kind of order 0BESSEL_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.
RESULT = BESSEL_Y0(X)
| X | The type shall be REAL, and it shall be scalar.
|
REAL. It has the same
kind as X.
program test_besy0
real(8) :: x = 0.0_8
x = bessel_y0(x)
end program test_besy0
| Name | Argument | Return type | Standard
|
DBESY0(X) | REAL(8) X | REAL(8) | GNU extension
|
BESSEL_Y1 — Bessel function of the second kind of order 1BESSEL_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.
RESULT = BESSEL_Y1(X)
| X | The type shall be REAL, and it shall be scalar.
|
REAL. It has the same
kind as X.
program test_besy1
real(8) :: x = 1.0_8
x = bessel_y1(x)
end program test_besy1
| Name | Argument | Return type | Standard
|
DBESY1(X) | REAL(8) X | REAL(8) | GNU extension
|
BESSEL_YN — Bessel function of the second kindBESSEL_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 N and X are arrays,
their ranks and shapes shall conform.
BESSEL_YN(N1, N2, X) returns an array with the Bessel functions
of the first kind of the orders N1 to N2.
BESSEL_YN(N1, N2, X)
RESULT = BESSEL_YN(N, X)
|
RESULT = BESSEL_YN(N1, N2, X)
|
| N | Shall be a scalar or an array of type INTEGER .
|
| N1 | Shall be a non-negative scalar of type INTEGER.
|
| N2 | Shall be a non-negative scalar of type INTEGER.
|
| X | Shall be a scalar or an array of type REAL;
for BESSEL_YN(N1, N2, X) it shall be scalar.
|
REAL. It has the same
kind as X.
program test_besyn
real(8) :: x = 1.0_8
x = bessel_yn(5,x)
end program test_besyn
| Name | Argument | Return type | Standard
|
DBESYN(N,X) | INTEGER N | REAL(8) | GNU extension
|
REAL(8) X |
|
BGE — Bitwise greater than or equal toRESULT = BGE(I, J)
| I | Shall be of INTEGER type.
|
| J | Shall be of INTEGER type, and of the same kind
as I.
|
LOGICAL and of the default kind.
BGT — Bitwise greater thanRESULT = BGT(I, J)
| I | Shall be of INTEGER type.
|
| J | Shall be of INTEGER type, and of the same kind
as I.
|
LOGICAL and of the default kind.
BIT_SIZE — Bit size inquiry functionBIT_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.
RESULT = BIT_SIZE(I)
| I | The type shall be INTEGER.
|
INTEGER
program test_bit_size
integer :: i = 123
integer :: size
size = bit_size(i)
print *, size
end program test_bit_size
BLE — Bitwise less than or equal toRESULT = BLE(I, J)
| I | Shall be of INTEGER type.
|
| J | Shall be of INTEGER type, and of the same kind
as I.
|
LOGICAL and of the default kind.
BLT — Bitwise less thanRESULT = BLT(I, J)
| I | Shall be of INTEGER type.
|
| J | Shall be of INTEGER type, and of the same kind
as I.
|
LOGICAL and of the default kind.
BTEST — Bit test functionBTEST(I,POS) returns logical .TRUE. if the bit at POS
in I is set. The counting of the bits starts at 0.
RESULT = BTEST(I, POS)
| I | The type shall be INTEGER.
|
| POS | The type shall be INTEGER.
|
LOGICAL
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
C_ASSOCIATED — Status of a C pointerC_ASSOCIATED(c_ptr_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.
RESULT = C_ASSOCIATED(c_ptr_1[, c_ptr_2])
| 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.
|
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.
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
C_F_POINTER — Convert C into Fortran pointerC_F_POINTER(CPTR, FPTR[, SHAPE]) assigns the target of the C pointer
CPTR to the Fortran pointer FPTR and specifies its shape.
CALL C_F_POINTER(CPTR, FPTR[, SHAPE])
| 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.
|
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
C_F_PROCPOINTER — Convert C into Fortran procedure pointerC_F_PROCPOINTER(CPTR, FPTR) Assign the target of the C function pointer
CPTR to the Fortran procedure pointer FPTR.
CALL C_F_PROCPOINTER(cptr, fptr)
| CPTR | scalar of the type C_FUNPTR. It is
INTENT(IN).
|
| FPTR | procedure pointer interoperable with cptr. It is
INTENT(OUT).
|
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
C_FUNLOC — Obtain the C address of a procedureC_FUNLOC(x) determines the C address of the argument.
RESULT = C_FUNLOC(x)
| x | Interoperable function or pointer to such function.
|
C_FUNPTR and contains the C address
of the argument.
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
C_LOC — Obtain the C address of an objectC_LOC(X) determines the C address of the argument.
RESULT = C_LOC(X)
| X | Shall have either the POINTER or TARGET attribute. It shall not be a coindexed object. It shall either be a variable with interoperable type and kind type parameters, or be a scalar, nonpolymorphic variable with no length type parameters.
|
C_PTR and contains the C address
of the argument.
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
C_SIZEOF — Size in bytes of an expressionC_SIZEOF(X) calculates the number of bytes of storage the
expression X occupies.
ISO_C_BINDING
N = C_SIZEOF(X)
| X | The argument shall be an interoperable data entity.
|
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 does not account for
the sizes of the data pointed to by these components.
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.
CEILING — Integer ceiling functionCEILING(A) returns the least integer greater than or equal to A.
RESULT = CEILING(A [, KIND])
| A | The type shall be REAL.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
INTEGER(KIND) if KIND is present
and a default-kind INTEGER otherwise.
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
CHAR — Character conversion functionCHAR(I [, KIND]) returns the character represented by the integer I.
RESULT = CHAR(I [, KIND])
| I | The type shall be INTEGER.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
CHARACTER(1)
program test_char
integer :: i = 74
character(1) :: c
c = char(i)
print *, i, c ! returns 'J'
end program test_char
| Name | Argument | Return type | Standard
|
CHAR(I) | INTEGER I | CHARACTER(LEN=1) | F77 and later
|
CHDIR — Change working directoryThis intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
CALL CHDIR(NAME [, STATUS])
|
STATUS = CHDIR(NAME)
|
| 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.
|
PROGRAM test_chdir
CHARACTER(len=255) :: path
CALL getcwd(path)
WRITE(*,*) TRIM(path)
CALL chdir("/tmp")
CALL getcwd(path)
WRITE(*,*) TRIM(path)
END PROGRAM
CHMOD — Change access permissions of filesCHMOD changes the permissions of a file.
This intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
CALL CHMOD(NAME, MODE[, STATUS])
|
STATUS = CHMOD(NAME, MODE)
|
| 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 chmod utility
as defined by the POSIX standard. The argument shall either be a string of
a nonnegative octal number or a symbolic mode.
|
| STATUS | (optional) scalar INTEGER, which is
0 on success and nonzero otherwise.
|
0 on success and nonzero
otherwise.
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
CMPLX — Complex conversion functionCMPLX(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.
RESULT = CMPLX(X [, Y [, KIND]])
| 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.
|
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.
program test_cmplx
integer :: i = 42
real :: x = 3.14
complex :: z
z = cmplx(i, x)
print *, z, cmplx(x)
end program test_cmplx
COMMAND_ARGUMENT_COUNT — Get number of command line argumentsCOMMAND_ARGUMENT_COUNT returns the number of arguments passed on the
command line when the containing program was invoked.
RESULT = COMMAND_ARGUMENT_COUNT()
| None
|
INTEGER of default kind.
program test_command_argument_count
integer :: count
count = command_argument_count()
print *, count
end program test_command_argument_count
COMPILER_OPTIONS — Options passed to the compilerCOMPILER_OPTIONS returns a string with the options used for
compiling.
ISO_FORTRAN_ENV
STR = COMPILER_OPTIONS()
COMPILER_OPTIONS intrinsic.
use iso_fortran_env
print '(4a)', 'This file was compiled by ', &
compiler_version(), ' using the options ', &
compiler_options()
end
COMPILER_VERSION — Compiler version stringCOMPILER_VERSION returns a string with the name and the
version of the compiler.
ISO_FORTRAN_ENV
STR = COMPILER_VERSION()
use iso_fortran_env
print '(4a)', 'This file was compiled by ', &
compiler_version(), ' using the options ', &
compiler_options()
end
COMPLEX — Complex conversion functionCOMPLEX(X, Y) returns a complex number where X is converted
to the real component and Y is converted to the imaginary
component.
RESULT = COMPLEX(X, Y)
| X | The type may be INTEGER or REAL.
|
| Y | The type may be INTEGER or REAL.
|
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.
program test_complex
integer :: i = 42
real :: x = 3.14
print *, complex(i, x)
end program test_complex
CONJG — Complex conjugate functionCONJG(Z) returns the conjugate of Z. If Z is (x, y)
then the result is (x, -y)
Z = CONJG(Z)
| Z | The type shall be COMPLEX.
|
COMPLEX.
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
| Name | Argument | Return type | Standard
|
CONJG(Z) | COMPLEX Z | COMPLEX | GNU extension
|
DCONJG(Z) | COMPLEX(8) Z | COMPLEX(8) | GNU extension
|
COS — Cosine functionCOS(X) computes the cosine of X.
RESULT = COS(X)
| X | The type shall be REAL or
COMPLEX.
|
REAL,
the return value lies in the range -1 \leq \cos (x) \leq 1.
program test_cos
real :: x = 0.0
x = cos(x)
end program test_cos
| Name | Argument | Return type | Standard
|
COS(X) | REAL(4) X | REAL(4) | Fortran 77 and later
|
DCOS(X) | REAL(8) X | REAL(8) | Fortran 77 and later
|
CCOS(X) | COMPLEX(4) X | COMPLEX(4) | Fortran 77 and later
|
ZCOS(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension
|
CDCOS(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension
|
COSH — Hyperbolic cosine functionCOSH(X) computes the hyperbolic cosine of X.
X = COSH(X)
| X | The type shall be REAL or COMPLEX.
|
REAL, the return value has a lower bound of one,
\cosh (x) \geq 1.
program test_cosh
real(8) :: x = 1.0_8
x = cosh(x)
end program test_cosh
| Name | Argument | Return type | Standard
|
COSH(X) | REAL(4) X | REAL(4) | Fortran 77 and later
|
DCOSH(X) | REAL(8) X | REAL(8) | Fortran 77 and later
|
COUNT — Count function.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.
RESULT = COUNT(MASK [, DIM, KIND])
| 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.
|
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.
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
CPU_TIME — CPU elapsed time in secondsREAL 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.
CALL CPU_TIME(TIME)
| TIME | The type shall be REAL with INTENT(OUT).
|
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
CSHIFT — Circular shift elements of an arrayCSHIFT(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.
RESULT = CSHIFT(ARRAY, SHIFT [, DIM])
| ARRAY | Shall be an array of any type.
|
| SHIFT | The type shall be INTEGER.
|
| DIM | The type shall be INTEGER.
|
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
CTIME — Convert a time into a stringCTIME converts a system time value, such as returned by
TIME8, to a string. The output will be 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.
CALL CTIME(TIME, RESULT).
|
RESULT = CTIME(TIME).
|
| TIME | The type shall be of type INTEGER.
|
| RESULT | The type shall be of type CHARACTER and
of default kind. It is an INTENT(OUT) argument. If the length
of this variable is too short for the time and date string to fit
completely, it will be blank on procedure return.
|
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
DATE_AND_TIME — Date and time subroutineDATE_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
|
CALL DATE_AND_TIME([DATE, TIME, ZONE, VALUES])
| 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).
|
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
DBLE — Double conversion functionDBLE(A) Converts A to double precision real type.
RESULT = DBLE(A)
| A | The type shall be INTEGER, REAL,
or COMPLEX.
|
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
DCMPLX — Double complex conversion functionDCMPLX(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.
RESULT = DCMPLX(X [, Y])
| X | The type may be INTEGER, REAL,
or COMPLEX.
|
| Y | (Optional if X is not COMPLEX.) May be
INTEGER or REAL.
|
COMPLEX(8)
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
DIGITS — Significant binary digits functionDIGITS(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.
RESULT = DIGITS(X)
| X | The type may be INTEGER or REAL.
|
INTEGER.
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
DIM — Positive differenceDIM(X,Y) returns the difference X-Y if the result is positive;
otherwise returns zero.
RESULT = DIM(X, Y)
| X | The type shall be INTEGER or REAL
|
| Y | The type shall be the same type and kind as X.
|
INTEGER or REAL.
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
| Name | Argument | Return type | Standard
|
DIM(X,Y) | REAL(4) X, Y | REAL(4) | Fortran 77 and later
|
IDIM(X,Y) | INTEGER(4) X, Y | INTEGER(4) | Fortran 77 and later
|
DDIM(X,Y) | REAL(8) X, Y | REAL(8) | Fortran 77 and later
|
DOT_PRODUCT — Dot product functionDOT_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).
RESULT = DOT_PRODUCT(VECTOR_A, VECTOR_B)
| 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.
|
INTEGER, REAL, or COMPLEX. If the arguments are
LOGICAL, the return value is .TRUE. or .FALSE..
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
DPROD — Double product functionDPROD(X,Y) returns the product X*Y.
RESULT = DPROD(X, Y)
| X | The type shall be REAL.
|
| Y | The type shall be REAL.
|
REAL(8).
program test_dprod
real :: x = 5.2
real :: y = 2.3
real(8) :: d
d = dprod(x,y)
print *, d
end program test_dprod
| Name | Argument | Return type | Standard
|
DPROD(X,Y) | REAL(4) X, Y | REAL(4) | Fortran 77 and later
|
DREAL — Double real part functionDREAL(Z) returns the real part of complex variable Z.
RESULT = DREAL(A)
| A | The type shall be COMPLEX(8).
|
REAL(8).
program test_dreal
complex(8) :: z = (1.3_8,7.2_8)
print *, dreal(z)
end program test_dreal
DSHIFTL — Combined left shiftDSHIFTL(I, J, SHIFT) combines bits of I and J. The
rightmost SHIFT bits of the result are the leftmost SHIFT
bits of J, and the remaining bits are the rightmost bits of
I.
RESULT = DSHIFTL(I, J, SHIFT)
| I | Shall be of type INTEGER or a BOZ constant.
|
| J | Shall be of type INTEGER or a BOZ constant.
If both I and J have integer type, then they shall have
the same kind type parameter. I and J shall not both be
BOZ constants.
|
| SHIFT | Shall be of type INTEGER. It shall
be nonnegative. If I is not a BOZ constant, then SHIFT
shall be less than or equal to BIT_SIZE(I); otherwise,
SHIFT shall be less than or equal to BIT_SIZE(J).
|
INT to an integer type with the
kind type parameter of the other.
DSHIFTR — Combined right shiftDSHIFTR(I, J, SHIFT) combines bits of I and J. The
leftmost SHIFT bits of the result are the rightmost SHIFT
bits of I, and the remaining bits are the leftmost bits of
J.
RESULT = DSHIFTR(I, J, SHIFT)
| I | Shall be of type INTEGER or a BOZ constant.
|
| J | Shall be of type INTEGER or a BOZ constant.
If both I and J have integer type, then they shall have
the same kind type parameter. I and J shall not both be
BOZ constants.
|
| SHIFT | Shall be of type INTEGER. It shall
be nonnegative. If I is not a BOZ constant, then SHIFT
shall be less than or equal to BIT_SIZE(I); otherwise,
SHIFT shall be less than or equal to BIT_SIZE(J).
|
INT to an integer type with the
kind type parameter of the other.
DTIME — Execution time subroutine (or function)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.
|
CALL DTIME(VALUES, TIME).
|
TIME = DTIME(VALUES), (not recommended).
|
| VALUES | The type shall be REAL(4), DIMENSION(2).
|
| TIME | The type shall be REAL(4).
|
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
EOSHIFT — End-off shift elements of an arrayEOSHIFT(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 Type | Boundary Value
|
| Numeric | 0 of the type and kind of ARRAY.
|
| Logical | .FALSE..
|
| Character(len) | len blanks.
|
RESULT = EOSHIFT(ARRAY, SHIFT [, BOUNDARY, DIM])
| ARRAY | May be any type, not scalar.
|
| SHIFT | The type shall be INTEGER.
|
| BOUNDARY | Same type as ARRAY.
|
| DIM | The type shall be INTEGER.
|
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
EPSILON — Epsilon functionEPSILON(X) returns the smallest number E of the same kind
as X such that 1 + E > 1.
RESULT = EPSILON(X)
| X | The type shall be REAL.
|
program test_epsilon
real :: x = 3.143
real(8) :: y = 2.33
print *, EPSILON(x)
print *, EPSILON(y)
end program test_epsilon
ERF — Error functionERF(X) computes the error function of X.
RESULT = ERF(X)
| X | The type shall be REAL.
|
REAL, of the same kind as
X and lies in the range -1 \leq erf (x) \leq 1 .
program test_erf
real(8) :: x = 0.17_8
x = erf(x)
end program test_erf
| Name | Argument | Return type | Standard
|
DERF(X) | REAL(8) X | REAL(8) | GNU extension
|
ERFC — Error functionERFC(X) computes the complementary error function of X.
RESULT = ERFC(X)
| X | The type shall be REAL.
|
REAL and of the same kind as X.
It lies in the range 0 \leq erfc (x) \leq 2 .
program test_erfc
real(8) :: x = 0.17_8
x = erfc(x)
end program test_erfc
| Name | Argument | Return type | Standard
|
DERFC(X) | REAL(8) X | REAL(8) | GNU extension
|
ERFC_SCALED — Error functionERFC_SCALED(X) computes the exponentially-scaled complementary
error function of X.
RESULT = ERFC_SCALED(X)
| X | The type shall be REAL.
|
REAL and of the same kind as X.
program test_erfc_scaled
real(8) :: x = 0.17_8
x = erfc_scaled(x)
end program test_erfc_scaled
ETIME — Execution time subroutine (or function)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.
|
CALL ETIME(VALUES, TIME).
|
TIME = ETIME(VALUES), (not recommended).
|
| VALUES | The type shall be REAL(4), DIMENSION(2).
|
| TIME | The type shall be REAL(4).
|
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
EXECUTE_COMMAND_LINE — Execute a shell commandEXECUTE_COMMAND_LINE runs a shell command, synchronously or
asynchronously.
The COMMAND argument is passed to the shell and executed, using
the C library's system call. (The shell is sh on Unix
systems, and cmd.exe on Windows.) If WAIT is present
and has the value false, the execution of the command is asynchronous
if the system supports it; otherwise, the command is executed
synchronously.
The three last arguments allow the user to get status information. After
synchronous execution, EXITSTAT contains the integer exit code of
the command, as returned by system. CMDSTAT is set to zero
if the command line was executed (whatever its exit status was).
CMDMSG is assigned an error message if an error has occurred.
Note that the system function need not be thread-safe. It is
the responsibility of the user to ensure that system is not
called concurrently.
CALL EXECUTE_COMMAND_LINE(COMMAND [, WAIT, EXITSTAT, CMDSTAT, CMDMSG ])
| COMMAND | Shall be a default CHARACTER scalar.
|
| WAIT | (Optional) Shall be a default LOGICAL scalar.
|
| EXITSTAT | (Optional) Shall be an INTEGER of the
default kind.
|
| CMDSTAT | (Optional) Shall be an INTEGER of the
default kind.
|
| CMDMSG | (Optional) Shall be an CHARACTER scalar of the
default kind.
|
program test_exec
integer :: i
call execute_command_line ("external_prog.exe", exitstat=i)
print *, "Exit status of external_prog.exe was ", i
call execute_command_line ("reindex_files.exe", wait=.false.)
print *, "Now reindexing files in the background"
end program test_exec
system
function call, its behavior with respect to signaling is processor
dependent. In particular, on POSIX-compliant systems, the SIGINT and
SIGQUIT signals will be ignored, and the SIGCHLD will be blocked. As
such, if the parent process is terminated, the child process might not be
terminated alongside.
EXIT — Exit the program with status.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.
CALL EXIT([STATUS])
| STATUS | Shall be an INTEGER of the default kind.
|
STATUS is passed to the parent process on exit.
program test_exit
integer :: STATUS = 0
print *, 'This program is going to exit.'
call EXIT(STATUS)
end program test_exit
EXP — Exponential functionEXP(X) computes the base e exponential of X.
RESULT = EXP(X)
| X | The type shall be REAL or
COMPLEX.
|
program test_exp
real :: x = 1.0
x = exp(x)
end program test_exp
| Name | Argument | Return type | Standard
|
EXP(X) | REAL(4) X | REAL(4) | Fortran 77 and later
|
DEXP(X) | REAL(8) X | REAL(8) | Fortran 77 and later
|
CEXP(X) | COMPLEX(4) X | COMPLEX(4) | Fortran 77 and later
|
ZEXP(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension
|
CDEXP(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension
|
EXPONENT — Exponent functionEXPONENT(X) returns the value of the exponent part of X. If X
is zero the value returned is zero.
RESULT = EXPONENT(X)
| X | The type shall be REAL.
|
INTEGER.
program test_exponent
real :: x = 1.0
integer :: i
i = exponent(x)
print *, i
print *, exponent(0.0)
end program test_exponent
EXTENDS_TYPE_OF — Query dynamic type for extensionRESULT = EXTENDS_TYPE_OF(A, MOLD)
| A | Shall be an object of extensible declared type or
unlimited polymorphic.
|
| MOLD | Shall be an object of extensible declared type or
unlimited polymorphic.
|
FDATE — Get the current time as a stringFDATE(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.
CALL FDATE(DATE).
|
DATE = FDATE().
|
| DATE | The type shall be of type CHARACTER of the
default kind. It is an INTENT(OUT) argument. If the length of
this variable is too short for the date and time string to fit
completely, it will be blank on procedure return.
|
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
FGET — Read a single character in stream mode from stdinThis 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 Fortran 2003 status.
CALL FGET(C [, STATUS])
|
STATUS = FGET(C)
|
| 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.
|
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
FGETC — Read a single character in stream modeThis 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 Fortran 2003 status.
CALL FGETC(UNIT, C [, STATUS])
|
STATUS = FGETC(UNIT, C)
|
| 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.
|
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
FLOOR — Integer floor functionFLOOR(A) returns the greatest integer less than or equal to X.
RESULT = FLOOR(A [, KIND])
| A | The type shall be REAL.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
INTEGER(KIND) if KIND is present
and of default-kind INTEGER otherwise.
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
FLUSH — Flush I/O unit(s)CALL FLUSH(UNIT)
| UNIT | (Optional) The type shall be INTEGER.
|
FLUSH
statement that should be preferred over the FLUSH intrinsic.
The FLUSH intrinsic and the Fortran 2003 FLUSH statement
have identical effect: they flush the runtime library's I/O buffer so
that the data becomes visible to other processes. This does not guarantee
that the data is committed to disk.
On POSIX systems, you can request that all data is transferred to the
storage device by calling the fsync function, with the POSIX file
descriptor of the I/O unit as argument (retrieved with GNU intrinsic
FNUM). The following example shows how:
! Declare the interface for POSIX fsync function
interface
function fsync (fd) bind(c,name="fsync")
use iso_c_binding, only: c_int
integer(c_int), value :: fd
integer(c_int) :: fsync
end function fsync
end interface
! Variable declaration
integer :: ret
! Opening unit 10
open (10,file="foo")
! ...
! Perform I/O on unit 10
! ...
! Flush and sync
flush(10)
ret = fsync(fnum(10))
! Handle possible error
if (ret /= 0) stop "Error calling FSYNC"
FNUM — File number functionFNUM(UNIT) returns the POSIX file descriptor number corresponding to the
open Fortran I/O unit UNIT.
RESULT = FNUM(UNIT)
| UNIT | The type shall be INTEGER.
|
INTEGER
program test_fnum
integer :: i
open (unit=10, status = "scratch")
i = fnum(10)
print *, i
close (10)
end program test_fnum
FPUT — Write a single character in stream mode to stdoutThis 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 Fortran 2003 status.
CALL FPUT(C [, STATUS])
|
STATUS = FPUT(C)
|
| 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.
|
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
FPUTC — Write a single character in stream modeThis 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 Fortran 2003 status.
CALL FPUTC(UNIT, C [, STATUS])
|
STATUS = FPUTC(UNIT, C)
|
| 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.
|
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
FRACTION — Fractional part of the model representationFRACTION(X) returns the fractional part of the model
representation of X.
Y = FRACTION(X)
| X | The type of the argument shall be a REAL.
|
X is returned;
it is X * RADIX(X)**(-EXPONENT(X)).
program test_fraction
real :: x
x = 178.1387e-4
print *, fraction(x), x * radix(x)**(-exponent(x))
end program test_fraction
FREE — Frees memoryMALLOC. 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.
CALL FREE(PTR)
| PTR | The type shall be INTEGER. It represents the
location of the memory that should be de-allocated.
|
MALLOC for an example.
FSEEK — Low level file positioning subroutineSEEK_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 Fortran 2003 status.
CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])
| 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).
|
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
FSTAT — Get file statusFSTAT is identical to STAT, except that information about an
already opened file is obtained.
The elements in VALUES are the same as described by STAT.
This intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
CALL FSTAT(UNIT, VALUES [, STATUS])
|
STATUS = FSTAT(UNIT, VALUES)
|
| 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.
|
FTELL — Current stream positionThis intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
CALL FTELL(UNIT, OFFSET)
|
OFFSET = FTELL(UNIT)
|
| OFFSET | Shall of type INTEGER.
|
| UNIT | Shall of type INTEGER.
|
PROGRAM test_ftell
INTEGER :: i
OPEN(10, FILE="temp.dat")
CALL ftell(10,i)
WRITE(*,*) i
END PROGRAM
GAMMA — Gamma functionGAMMA(X) computes Gamma (\Gamma) of X. For positive,
integer values of X the Gamma function simplifies to the factorial
function \Gamma(x)=(x-1)!.
X = GAMMA(X)
| X | Shall be of type REAL and neither zero
nor a negative integer.
|
REAL of the same kind as X.
program test_gamma
real :: x = 1.0
x = gamma(x) ! returns 1.0
end program test_gamma
| Name | Argument | Return type | Standard
|
GAMMA(X) | REAL(4) X | REAL(4) | GNU Extension
|
DGAMMA(X) | REAL(8) X | REAL(8) | GNU Extension
|
GERROR — Get last system error messagestrerror(3) in C.
CALL GERROR(RESULT)
| RESULT | Shall of type CHARACTER and of default
|
PROGRAM test_gerror
CHARACTER(len=100) :: msg
CALL gerror(msg)
WRITE(*,*) msg
END PROGRAM
GETARG — Get command line argumentsThis intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use of
the GET_COMMAND_ARGUMENT intrinsic defined by the Fortran 2003
standard.
CALL GETARG(POS, VALUE)
| 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.
|
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).
PROGRAM test_getarg
INTEGER :: i
CHARACTER(len=32) :: arg
DO i = 1, iargc()
CALL getarg(i, arg)
WRITE (*,*) arg
END DO
END PROGRAM
Fortran 2003 functions and subroutines: GET_COMMAND, GET_COMMAND_ARGUMENT, COMMAND_ARGUMENT_COUNT
GET_COMMAND — Get the entire command lineCALL GET_COMMAND([COMMAND, LENGTH, STATUS])
| 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.
|
PROGRAM test_get_command
CHARACTER(len=255) :: cmd
CALL get_command(cmd)
WRITE (*,*) TRIM(cmd)
END PROGRAM
GET_COMMAND_ARGUMENT — Get command line argumentsCALL GET_COMMAND_ARGUMENT(NUMBER [, VALUE, LENGTH, STATUS])
| NUMBER | Shall be a scalar of type INTEGER and of
default kind, NUMBER \geq 0
|
| VALUE | (Optional) Shall be a scalar of type CHARACTER
and of default kind.
|
| LENGTH | (Optional) Shall be a scalar of type INTEGER
and of default kind.
|
| STATUS | (Optional) Shall be a scalar of type INTEGER
and of default kind.
|
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.
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
GETCWD — Get current working directoryThis intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
CALL GETCWD(C [, STATUS])
|
STATUS = GETCWD(C)
|
| 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.
|
PROGRAM test_getcwd
CHARACTER(len=255) :: cwd
CALL getcwd(cwd)
WRITE(*,*) TRIM(cwd)
END PROGRAM
GETENV — Get an environmental variableThis intrinsic routine is provided for backwards compatibility with GNU Fortran 77. In new code, programmers should consider the use of the GET_ENVIRONMENT_VARIABLE intrinsic defined by the Fortran 2003 standard.
Note that GETENV need not be thread-safe. It is the
responsibility of the user to ensure that the environment is not being
updated concurrently with a call to the GETENV intrinsic.
CALL GETENV(NAME, VALUE)
| NAME | Shall be of type CHARACTER and of default kind.
|
| VALUE | Shall be of type CHARACTER and of default kind.
|
PROGRAM test_getenv
CHARACTER(len=255) :: homedir
CALL getenv("HOME", homedir)
WRITE (*,*) TRIM(homedir)
END PROGRAM
GET_ENVIRONMENT_VARIABLE — Get an environmental variableNote that GET_ENVIRONMENT_VARIABLE need not be thread-safe. It
is the responsibility of the user to ensure that the environment is
not being updated concurrently with a call to the
GET_ENVIRONMENT_VARIABLE intrinsic.
CALL GET_ENVIRONMENT_VARIABLE(NAME[, VALUE, LENGTH, STATUS, TRIM_NAME)
| NAME | Shall be a scalar of type CHARACTER
and of default kind.
|
| VALUE | (Optional) Shall be a scalar of type CHARACTER
and of default kind.
|
| LENGTH | (Optional) Shall be a scalar of type INTEGER
and of default kind.
|
| STATUS | (Optional) Shall be a scalar of type INTEGER
and of default kind.
|
| TRIM_NAME | (Optional) Shall be a scalar of type LOGICAL
and of default kind.
|
.FALSE., the trailing blanks in NAME
are significant; otherwise they are not part of the environment variable
name.
PROGRAM test_getenv
CHARACTER(len=255) :: homedir
CALL get_environment_variable("HOME", homedir)
WRITE (*,*) TRIM(homedir)
END PROGRAM
GETGID — Group ID functionRESULT = GETGID()
GETGID is an INTEGER of the default
kind.
GETPID for an example.
GETLOG — Get login nameCALL GETLOG(C)
| C | Shall be of type CHARACTER and of default kind.
|
geteuid and getpwuid are not available, and
the getlogin function is not implemented either, this will
return a blank string.)
PROGRAM TEST_GETLOG
CHARACTER(32) :: login
CALL GETLOG(login)
WRITE(*,*) login
END PROGRAM
GETPID — Process ID functionRESULT = GETPID()
GETPID is an INTEGER of the default
kind.
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
GETUID — User ID functionRESULT = GETUID()
GETUID is an INTEGER of the default
kind.
GETPID for an example.
GMTIME — Convert time to GMT infoTIME8
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).
CALL GMTIME(TIME, VALUES)
| TIME | An INTEGER scalar expression
corresponding to a system time, with INTENT(IN).
|
| VALUES | A default INTEGER array with 9 elements,
with INTENT(OUT).
|
HOSTNM — Get system host nameThis intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
CALL HOSTNM(C [, STATUS])
|
STATUS = HOSTNM(NAME)
|
| 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.
|
HUGE — Largest number of a kindHUGE(X) returns the largest number that is not an infinity in
the model of the type of X.
RESULT = HUGE(X)
| X | Shall be of type REAL or INTEGER.
|
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
HYPOT — Euclidean distance functionHYPOT(X,Y) is the Euclidean distance function. It is equal to
\sqrtX^2 + Y^2, without undue underflow or overflow.
RESULT = HYPOT(X, Y)
| X | The type shall be REAL.
|
| Y | The type and kind type parameter shall be the same as
X.
|
program test_hypot
real(4) :: x = 1.e0_4, y = 0.5e0_4
x = hypot(x,y)
end program test_hypot
IACHAR — Code in ASCII collating sequenceIACHAR(C) returns the code for the ASCII character
in the first character position of C.
RESULT = IACHAR(C [, KIND])
| C | Shall be a scalar CHARACTER, with INTENT(IN)
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
program test_iachar
integer i
i = iachar(' ')
end program test_iachar
IALL — Bitwise AND of array elementsTRUE.
RESULT = IALL(ARRAY[, MASK])
|
RESULT = IALL(ARRAY, DIM[, MASK])
|
| ARRAY | Shall be an array of type INTEGER
|
| 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.
|
If DIM is absent, a scalar with the bitwise ALL 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.
PROGRAM test_iall
INTEGER(1) :: a(2)
a(1) = b'00100100'
a(2) = b'01101010'
! prints 00100000
PRINT '(b8.8)', IALL(a)
END PROGRAM
IAND — Bitwise logical andAND.
RESULT = IAND(I, J)
| 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.)
|
INTEGER, of the same kind as the
arguments. (If the argument kinds differ, it is of the same kind as
the larger argument.)
PROGRAM test_iand
INTEGER :: a, b
DATA a / Z'F' /, b / Z'3' /
WRITE (*,*) IAND(a, b)
END PROGRAM
IANY — Bitwise OR of array elementsTRUE.
RESULT = IANY(ARRAY[, MASK])
|
RESULT = IANY(ARRAY, DIM[, MASK])
|
| ARRAY | Shall be an array of type INTEGER
|
| 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.
|
If DIM is absent, a scalar with the bitwise OR 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.
PROGRAM test_iany
INTEGER(1) :: a(2)
a(1) = b'00100100'
a(2) = b'01101010'
! prints 01101110
PRINT '(b8.8)', IANY(a)
END PROGRAM
IARGC — Get the number of command line argumentsIARGC 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 COMMAND_ARGUMENT_COUNT intrinsic defined by the Fortran 2003
standard.
RESULT = IARGC()
INTEGER(4).
Fortran 2003 functions and subroutines: GET_COMMAND, GET_COMMAND_ARGUMENT, COMMAND_ARGUMENT_COUNT
IBCLR — Clear bitIBCLR returns the value of I with the bit at position
POS set to zero.
RESULT = IBCLR(I, POS)
| I | The type shall be INTEGER.
|
| POS | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
IBITS — Bit extractionIBITS 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).
RESULT = IBITS(I, POS, LEN)
| I | The type shall be INTEGER.
|
| POS | The type shall be INTEGER.
|
| LEN | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
IBSET — Set bitIBSET returns the value of I with the bit at position
POS set to one.
RESULT = IBSET(I, POS)
| I | The type shall be INTEGER.
|
| POS | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
ICHAR — Character-to-integer conversion functionICHAR(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.
RESULT = ICHAR(C [, KIND])
| C | Shall be a scalar CHARACTER, with INTENT(IN)
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
program test_ichar
integer i
i = ichar(' ')
end program test_ichar
| Name | Argument | Return type | Standard
|
ICHAR(C) | CHARACTER C | INTEGER(4) | Fortran 77 and later
|
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
IDATE — Get current local time subroutine (day/month/year)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.
CALL IDATE(VALUES)
| VALUES | The type shall be INTEGER, DIMENSION(3) and
the kind shall be the default integer kind.
|
program test_idate
integer, dimension(3) :: tarray
call idate(tarray)
print *, tarray(1)
print *, tarray(2)
print *, tarray(3)
end program test_idate
IEOR — Bitwise logical exclusive orIEOR returns the bitwise Boolean exclusive-OR of I and
J.
RESULT = IEOR(I, J)
| 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.)
|
INTEGER, of the same kind as the
arguments. (If the argument kinds differ, it is of the same kind as
the larger argument.)
IERRNO — Get the last system error numbererrno
variable.
RESULT = IERRNO()
INTEGER and of the default integer
kind.
IMAGE_INDEX — Function that converts a cosubscript to an image indexRESULT = IMAGE_INDEX(COARRAY, SUB)
| COARRAY | Coarray of any type.
|
| SUB | default integer rank-1 array of a size equal to
the corank of COARRAY.
|
INTEGER :: array[2,-1:4,8,*]
! Writes 28 (or 0 if there are fewer than 28 images)
WRITE (*,*) IMAGE_INDEX (array, [2,0,3,1])
INDEX — Position of a substring within a stringRESULT = INDEX(STRING, SUBSTRING [, BACK [, KIND]])
| 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.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
| Name | Argument | Return type | Standard
|
INDEX(STRING, SUBSTRING) | CHARACTER | INTEGER(4) | Fortran 77 and later
|
INT — Convert to integer typeRESULT = INT(A [, KIND))
| A | Shall be of type INTEGER,
REAL, or COMPLEX.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
INTEGER variable or array under
the following rules:
INTEGER, INT(A) = A
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.
COMPLEX, rule B is applied to the real part of A.
program test_int
integer :: i = 42
complex :: z = (-3.7, 1.0)
print *, int(i)
print *, int(z), int(z,8)
end program
| Name | Argument | Return type | Standard
|
INT(A) | REAL(4) A | INTEGER | Fortran 77 and later
|
IFIX(A) | REAL(4) A | INTEGER | Fortran 77 and later
|
IDINT(A) | REAL(8) A | INTEGER | Fortran 77 and later
|
INT2 — Convert to 16-bit integer typeKIND=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.
RESULT = INT2(A)
| A | Shall be of type INTEGER,
REAL, or COMPLEX.
|
INTEGER(2) variable.
INT8 — Convert to 64-bit integer typeKIND=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.
RESULT = INT8(A)
| A | Shall be of type INTEGER,
REAL, or COMPLEX.
|
INTEGER(8) variable.
IOR — Bitwise logical orIOR returns the bitwise Boolean inclusive-OR of I and
J.
RESULT = IOR(I, J)
| 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.)
|
INTEGER, of the same kind as the
arguments. (If the argument kinds differ, it is of the same kind as
the larger argument.)
IPARITY — Bitwise XOR of array elementsTRUE.
RESULT = IPARITY(ARRAY[, MASK])
|
RESULT = IPARITY(ARRAY, DIM[, MASK])
|
| ARRAY | Shall be an array of type INTEGER
|
| 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.
|
If DIM is absent, a scalar with the bitwise XOR 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.
PROGRAM test_iparity
INTEGER(1) :: a(2)
a(1) = b'00100100'
a(2) = b'01101010'
! prints 01001110
PRINT '(b8.8)', IPARITY(a)
END PROGRAM
IRAND — Integer pseudo-random numberIRAND(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
RANDOM_NUMBER as it implements a superior algorithm.
RESULT = IRAND(I)
| I | Shall be a scalar INTEGER of kind 4.
|
INTEGER(kind=4) type.
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
IS_IOSTAT_END — Test for end-of-file valueIS_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.
RESULT = IS_IOSTAT_END(I)
| I | Shall be of the type INTEGER.
|
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.
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
IS_IOSTAT_EOR — Test for end-of-record valueIS_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.
RESULT = IS_IOSTAT_EOR(I)
| I | Shall be of the type INTEGER.
|
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.
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
ISATTY — Whether a unit is a terminal device.RESULT = ISATTY(UNIT)
| UNIT | Shall be a scalar INTEGER.
|
.TRUE. if the UNIT is connected to a terminal
device, .FALSE. otherwise.
PROGRAM test_isatty
INTEGER(kind=1) :: unit
DO unit = 1, 10
write(*,*) isatty(unit=unit)
END DO
END PROGRAM
ISHFT — Shift bitsISHFT 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.
RESULT = ISHFT(I, SHIFT)
| I | The type shall be INTEGER.
|
| SHIFT | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
ISHFTC — Shift bits circularlyISHFTC 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).
RESULT = ISHFTC(I, SHIFT [, SIZE])
| 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).
|
INTEGER and of the same kind as
I.
ISNAN — Test for a NaNISNAN tests whether a floating-point value is an IEEE
Not-a-Number (NaN).
ISNAN(X)
| X | Variable of the type REAL.
|
LOGICAL. The returned value is TRUE
if X is a NaN and FALSE otherwise.
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
ITIME — Get current local time subroutine (hour/minutes/seconds)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.
CALL ITIME(VALUES)
| VALUES | The type shall be INTEGER, DIMENSION(3)
and the kind shall be the default integer kind.
|
program test_itime
integer, dimension(3) :: tarray
call itime(tarray)
print *, tarray(1)
print *, tarray(2)
print *, tarray(3)
end program test_itime
KILL — Send a signal to a processkill(2).
This intrinsic is provided in both subroutine and function forms; however,
only one form can be used in any given program unit.
CALL KILL(C, VALUE [, STATUS])
|
STATUS = KILL(C, VALUE)
|
| 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.
|
KIND — Kind of an entityKIND(X) returns the kind value of the entity X.
K = KIND(X)
| X | Shall be of type LOGICAL, INTEGER,
REAL, COMPLEX or CHARACTER.
|
INTEGER and of the default
integer kind.
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
LBOUND — Lower dimension bounds of an arrayRESULT = LBOUND(ARRAY [, DIM [, KIND]])
| 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.
|
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.
LCOBOUND — Lower codimension bounds of an arrayRESULT = LCOBOUND(COARRAY [, DIM [, KIND]])
| ARRAY | Shall be an coarray, of any type.
|
| DIM | (Optional) Shall be a scalar INTEGER.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
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 cobounds of
COARRAY. If DIM is present, the result is a scalar
corresponding to the lower cobound of the array along that codimension.
LEADZ — Number of leading zero bits of an integerLEADZ returns the number of leading zero bits of an integer.
RESULT = LEADZ(I)
| I | Shall be of type INTEGER.
|
INTEGER.
If all the bits of I are zero, the result value is BIT_SIZE(I).
PROGRAM test_leadz
WRITE (*,*) BIT_SIZE(1) ! prints 32
WRITE (*,*) LEADZ(1) ! prints 31
END PROGRAM
LEN — Length of a character entityL = LEN(STRING [, KIND])
| 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.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
| Name | Argument | Return type | Standard
|
LEN(STRING) | CHARACTER | INTEGER | Fortran 77 and later
|
LEN_TRIM — Length of a character entity without trailing blank charactersRESULT = LEN_TRIM(STRING [, KIND])
| STRING | Shall be a scalar of type CHARACTER,
with INTENT(IN)
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
LGE — Lexical greater than or equalIn 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.
RESULT = LGE(STRING_A, STRING_B)
| STRING_A | Shall be of default CHARACTER type.
|
| STRING_B | Shall be of default CHARACTER type.
|
.TRUE. if STRING_A >= STRING_B, and .FALSE.
otherwise, based on the ASCII ordering.
| Name | Argument | Return type | Standard
|
LGE(STRING_A, STRING_B) | CHARACTER | LOGICAL | Fortran 77 and later
|
LGT — Lexical greater thanIn 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.
RESULT = LGT(STRING_A, STRING_B)
| STRING_A | Shall be of default CHARACTER type.
|
| STRING_B | Shall be of default CHARACTER type.
|
.TRUE. if STRING_A > STRING_B, and .FALSE.
otherwise, based on the ASCII ordering.
| Name | Argument | Return type | Standard
|
LGT(STRING_A, STRING_B) | CHARACTER | LOGICAL | Fortran 77 and later
|
LINK — Create a hard linkCHAR(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.
CALL LINK(PATH1, PATH2 [, STATUS])
|
STATUS = LINK(PATH1, PATH2)
|
| PATH1 | Shall be of default CHARACTER type.
|
| PATH2 | Shall be of default CHARACTER type.
|
| STATUS | (Optional) Shall be of default INTEGER type.
|
LLE — Lexical less than or equalIn 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.
RESULT = LLE(STRING_A, STRING_B)
| STRING_A | Shall be of default CHARACTER type.
|
| STRING_B | Shall be of default CHARACTER type.
|
.TRUE. if STRING_A <= STRING_B, and .FALSE.
otherwise, based on the ASCII ordering.
| Name | Argument | Return type | Standard
|
LLE(STRING_A, STRING_B) | CHARACTER | LOGICAL | Fortran 77 and later
|
LLT — Lexical less thanIn 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.
RESULT = LLT(STRING_A, STRING_B)
| STRING_A | Shall be of default CHARACTER type.
|
| STRING_B | Shall be of default CHARACTER type.
|
.TRUE. if STRING_A < STRING_B, and .FALSE.
otherwise, based on the ASCII ordering.
| Name | Argument | Return type | Standard
|
LLT(STRING_A, STRING_B) | CHARACTER | LOGICAL | Fortran 77 and later
|
LNBLNK — Index of the last non-blank character in a stringLEN_TRIM intrinsic, and is only
included for backwards compatibility.
RESULT = LNBLNK(STRING)
| STRING | Shall be a scalar of type CHARACTER,
with INTENT(IN)
|
INTEGER(kind=4) type.
LOC — Returns the address of a variableLOC(X) returns the address of X as an integer.
RESULT = LOC(X)
| X | Variable of any type.
|
INTEGER, with a KIND
corresponding to the size (in bytes) of a memory address on the target
machine.
program test_loc
integer :: i
real :: r
i = loc(r)
print *, i
end program test_loc
LOG — Natural logarithm functionLOG(X) computes the natural logarithm of X, i.e. the
logarithm to the base e.
RESULT = LOG(X)
| X | The type shall be REAL or
COMPLEX.
|
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.
program test_log
real(8) :: x = 2.7182818284590451_8
complex :: z = (1.0, 2.0)
x = log(x) ! will yield (approximately) 1
z = log(z)
end program test_log
| 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) X | COMPLEX(4) | f95, gnu
|
ZLOG(X) | COMPLEX(8) X | COMPLEX(8) | f95, gnu
|
CDLOG(X) | COMPLEX(8) X | COMPLEX(8) | f95, gnu
|
LOG10 — Base 10 logarithm functionLOG10(X) computes the base 10 logarithm of X.
RESULT = LOG10(X)
| X | The type shall be REAL.
|
REAL or COMPLEX.
The kind type parameter is the same as X.
program test_log10
real(8) :: x = 10.0_8
x = log10(x)
end program test_log10
| 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
|
LOG_GAMMA — Logarithm of the Gamma functionLOG_GAMMA(X) computes the natural logarithm of the absolute value
of the Gamma (\Gamma) function.
X = LOG_GAMMA(X)
| X | Shall be of type REAL and neither zero
nor a negative integer.
|
REAL of the same kind as X.
program test_log_gamma
real :: x = 1.0
x = lgamma(x) ! returns 0.0
end program test_log_gamma
| 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
|
LOGICAL — Convert to logical typeLOGICAL variable to another.
RESULT = LOGICAL(L [, KIND])
| L | The type shall be LOGICAL.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
LOGICAL value equal to L, with a
kind corresponding to KIND, or of the default logical kind if
KIND is not given.
LONG — Convert to integer typeKIND=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.
RESULT = LONG(A)
| A | Shall be of type INTEGER,
REAL, or COMPLEX.
|
INTEGER(4) variable.
LSHIFT — Left shift bitsLSHIFT 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, and the SHIFTL intrinsic,
which is standard in Fortran 2008 and later.
RESULT = LSHIFT(I, SHIFT)
| I | The type shall be INTEGER.
|
| SHIFT | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
LSTAT — Get file statusLSTAT is identical to 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 STAT.
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
CALL LSTAT(NAME, VALUES [, STATUS])
|
STATUS = LSTAT(NAME, VALUES)
|
| 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.
|
LTIME — Convert time to local time infoTIME8
intrinsic), fills VALUES with values extracted from it appropriate
to the local time zone using localtime(3).
CALL LTIME(TIME, VALUES)
| TIME | An INTEGER scalar expression
corresponding to a system time, with INTENT(IN).
|
| VALUES | A default INTEGER array with 9 elements,
with INTENT(OUT).
|
MALLOC — Allocate dynamic memoryMALLOC(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.
PTR = MALLOC(SIZE)
| SIZE | The type shall be INTEGER.
|
INTEGER(K), with K such that
variables of type INTEGER(K) have the same size as
C pointers (sizeof(void *)).
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
MASKL — Left justified maskMASKL(I[, KIND]) has its leftmost I bits set to 1, and the
remaining bits set to 0.
RESULT = MASKL(I[, KIND])
| I | Shall be of type INTEGER.
|
| KIND | Shall be a scalar constant expression of type
INTEGER.
|
INTEGER. If KIND is present, it
specifies the kind value of the return type; otherwise, it is of the
default integer kind.
MASKR — Right justified maskMASKL(I[, KIND]) has its rightmost I bits set to 1, and the
remaining bits set to 0.
RESULT = MASKR(I[, KIND])
| I | Shall be of type INTEGER.
|
| KIND | Shall be a scalar constant expression of type
INTEGER.
|
INTEGER. If KIND is present, it
specifies the kind value of the return type; otherwise, it is of the
default integer kind.
MATMUL — matrix multiplicationRESULT = MATMUL(MATRIX_A, MATRIX_B)
| 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.
|
* or .AND. operators.
MAX — Maximum value of an argument listRESULT = MAX(A1, A2 [, A3 [, ...]])
| 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.)
|
| Name | Argument | Return type | Standard
|
MAX0(A1) | INTEGER(4) A1 | INTEGER(4) | Fortran 77 and later
|
AMAX0(A1) | INTEGER(4) A1 | REAL(MAX(X)) | Fortran 77 and later
|
MAX1(A1) | REAL A1 | INT(MAX(X)) | Fortran 77 and later
|
AMAX1(A1) | REAL(4) A1 | REAL(4) | Fortran 77 and later
|
DMAX1(A1) | REAL(8) A1 | REAL(8) | Fortran 77 and later
|
MAXEXPONENT — Maximum exponent of a real kindMAXEXPONENT(X) returns the maximum exponent in the model of the
type of X.
RESULT = MAXEXPONENT(X)
| X | Shall be of type REAL.
|
INTEGER and of the default integer
kind.
program exponents
real(kind=4) :: x
real(kind=8) :: y
print *, minexponent(x), maxexponent(x)
print *, minexponent(y), maxexponent(y)
end program exponents
MAXLOC — Location of the maximum value within an array.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.
RESULT = MAXLOC(ARRAY, DIM [, MASK])
|
RESULT = MAXLOC(ARRAY [, MASK])
|
| 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.
|
INTEGER type.
MAXVAL — Maximum value of an array.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.
RESULT = MAXVAL(ARRAY, DIM [, MASK])
|
RESULT = MAXVAL(ARRAY [, MASK])
|
| 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.
|
MCLOCK — Time functionclock(3) in the C standard library.
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.
RESULT = MCLOCK()
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).
MCLOCK8 — Time function (64-bit)clock(3) in the C standard library.
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.
RESULT = MCLOCK8()
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).
MERGE — Merge variables.TRUE., or equal to
FSOURCE if it is .FALSE..
RESULT = MERGE(TSOURCE, FSOURCE, MASK)
| TSOURCE | May be of any type.
|
| FSOURCE | Shall be of the same type and type parameters
as TSOURCE.
|
| MASK | Shall be of type LOGICAL.
|
MERGE_BITS — Merge of bits under maskMERGE_BITS(I, J, MASK) merges the bits of I and J
as determined by the mask. The i-th bit of the result is equal to the
i-th bit of I if the i-th bit of MASK is 1; it is equal to
the i-th bit of J otherwise.
RESULT = MERGE_BITS(I, J, MASK)
| I | Shall be of type INTEGER.
|
| J | Shall be of type INTEGER and of the same
kind as I.
|
| MASK | Shall be of type INTEGER and of the same
kind as I.
|
MIN — Minimum value of an argument listRESULT = MIN(A1, A2 [, A3, ...])
| 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.)
|
| Name | Argument | Return type | Standard
|
MIN0(A1) | INTEGER(4) A1 | INTEGER(4) | Fortran 77 and later
|
AMIN0(A1) | INTEGER(4) A1 | REAL(4) | Fortran 77 and later
|
MIN1(A1) | REAL A1 | INTEGER(4) | Fortran 77 and later
|
AMIN1(A1) | REAL(4) A1 | REAL(4) | Fortran 77 and later
|
DMIN1(A1) | REAL(8) A1 | REAL(8) | Fortran 77 and later
|
MINEXPONENT — Minimum exponent of a real kindMINEXPONENT(X) returns the minimum exponent in the model of the
type of X.
RESULT = MINEXPONENT(X)
| X | Shall be of type REAL.
|
INTEGER and of the default integer
kind.
MAXEXPONENT for an example.
MINLOC — Location of the minimum value within an array.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.
RESULT = MINLOC(ARRAY, DIM [, MASK])
|
RESULT = MINLOC(ARRAY [, MASK])
|
| 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.
|
INTEGER type.
MINVAL — Minimum value of an array.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.
RESULT = MINVAL(ARRAY, DIM [, MASK])
|
RESULT = MINVAL(ARRAY [, MASK])
|
| 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.
|
MOD — Remainder functionMOD(A,P) computes the remainder of the division of A by P.
RESULT = MOD(A, P)
| A | Shall be a scalar of type INTEGER or REAL.
|
| P | Shall be a scalar of the same type and kind as A
and not equal to zero.
|
A - (INT(A/P) * P). The type
and kind of the return value is the same as that of the arguments. The
returned value has the same sign as A and a magnitude less than the
magnitude of P.
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
| Name | Arguments | Return type | Standard
|
MOD(A,P) | INTEGER A,P | INTEGER | Fortran 95 and later
|
AMOD(A,P) | REAL(4) A,P | REAL(4) | Fortran 95 and later
|
DMOD(A,P) | REAL(8) A,P | REAL(8) | Fortran 95 and later
|
MODULO — Modulo functionMODULO(A,P) computes the A modulo P.
RESULT = MODULO(A, P)
| A | Shall be a scalar of type INTEGER or REAL.
|
| P | Shall be a scalar of the same type and kind as A.
It shall not be zero.
|
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).
REAL:MODULO(A,P) has the value of A - FLOOR (A / P) * P.
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
MOVE_ALLOC — Move allocation from one object to anotherMOVE_ALLOC(FROM, TO) moves the allocation from FROM to
TO. FROM will become deallocated in the process.
CALL MOVE_ALLOC(FROM, TO)
| 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.
|
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
MVBITS — Move bits from one integer to anotherFROMPOS+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).
CALL MVBITS(FROM, FROMPOS, LEN, TO, TOPOS)
| 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.
|
NEAREST — Nearest representable numberNEAREST(X, S) returns the processor-representable number nearest
to X in the direction indicated by the sign of S.
RESULT = NEAREST(X, S)
| X | Shall be of type REAL.
|
| S | Shall be of type REAL and
not equal to zero.
|
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.
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
NEW_LINE — New line characterNEW_LINE(C) returns the new-line character.
RESULT = NEW_LINE(C)
| C | The argument shall be a scalar or array of the
type CHARACTER.
|
program newline
implicit none
write(*,'(A)') 'This is record 1.'//NEW_LINE('A')//'This is record 2.'
end program newline
NINT — Nearest whole numberNINT(A) rounds its argument to the nearest whole number.
RESULT = NINT(A [, KIND])
| A | The type of the argument shall be REAL.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
INTEGER of the default kind.
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
| Name | Argument | Return Type | Standard
|
NINT(A) | REAL(4) A | INTEGER | Fortran 95 and later
|
IDNINT(A) | REAL(8) A | INTEGER | Fortran 95 and later
|
NORM2 — Euclidean vector normsRESULT = NORM2(ARRAY[, DIM])
|
| ARRAY | Shall be an array of type REAL
|
| 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.
|
If DIM is absent, a scalar with the square root of the sum of all
elements in ARRAY squared 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.
PROGRAM test_sum
REAL :: x(5) = [ real :: 1, 2, 3, 4, 5 ]
print *, NORM2(x) ! = sqrt(55.) ~ 7.416
END PROGRAM
NOT — Logical negationNOT returns the bitwise Boolean inverse of I.
RESULT = NOT(I)
| I | The type shall be INTEGER.
|
INTEGER, of the same kind as the
argument.
NULL — Function that returns an disassociated pointerIf MOLD is present, a disassociated 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.
PTR => NULL([MOLD])
| MOLD | (Optional) shall be a pointer of any association
status and of any type.
|
REAL, POINTER, DIMENSION(:) :: VEC => NULL ()
NUM_IMAGES — Function that returns the number of imagesRESULT = NUM_IMAGES()
INTEGER :: value[*]
INTEGER :: i
value = THIS_IMAGE()
SYNC ALL
IF (THIS_IMAGE() == 1) THEN
DO i = 1, NUM_IMAGES()
WRITE(*,'(2(a,i0))') 'value[', i, '] is ', value[i]
END DO
END IF
OR — Bitwise logical OROR.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. For integer arguments, programmers should consider
the use of the IOR intrinsic defined by the Fortran standard.
RESULT = OR(I, J)
| 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.
|
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.
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
PACK — Pack an array into an array of rank oneThe beginning of the resulting array is made up of elements whose MASK
equals TRUE. Afterwards, positions are filled with elements taken from
VECTOR.
RESULT = PACK(ARRAY, MASK[,VECTOR])
| 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.
|
TRUE values in MASK otherwise.
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
PARITY — Reduction with exclusive OR.XOR.,
of MASK along dimension DIM.
RESULT = PARITY(MASK[, DIM])
|
| LOGICAL | Shall be an array of type LOGICAL
|
| 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 MASK.
|
If DIM is absent, a scalar with the parity of all elements in
MASK is returned, i.e. true if an odd number of elements is
.true. and false otherwise. If DIM is present, an array
of rank n-1, where n equals the rank of ARRAY,
and a shape similar to that of MASK with dimension DIM
dropped is returned.
PROGRAM test_sum
LOGICAL :: x(2) = [ .true., .false. ]
print *, PARITY(x) ! prints "T" (true).
END PROGRAM
PERROR — Print system error messagestderr 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).
CALL PERROR(STRING)
| STRING | A scalar of type CHARACTER and of the
default kind.
|
POPCNT — Number of bits setPOPCNT(I) returns the number of bits set ('1' bits) in the binary
representation of I.
RESULT = POPCNT(I)
| I | Shall be of type INTEGER.
|
INTEGER and of the default integer
kind.
program test_population
print *, popcnt(127), poppar(127)
print *, popcnt(huge(0_4)), poppar(huge(0_4))
print *, popcnt(huge(0_8)), poppar(huge(0_8))
end program test_population
POPPAR — Parity of the number of bits setPOPPAR(I) returns parity of the integer I, i.e. the parity
of the number of bits set ('1' bits) in the binary representation of
I. It is equal to 0 if I has an even number of bits set,
and 1 for an odd number of '1' bits.
RESULT = POPPAR(I)
| I | Shall be of type INTEGER.
|
INTEGER and of the default integer
kind.
program test_population
print *, popcnt(127), poppar(127)
print *, popcnt(huge(0_4)), poppar(huge(0_4))
print *, popcnt(huge(0_8)), poppar(huge(0_8))
end program test_population
PRECISION — Decimal precision of a real kindPRECISION(X) returns the decimal precision in the model of the
type of X.
RESULT = PRECISION(X)
| X | Shall be of type REAL or COMPLEX.
|
INTEGER and of the default integer
kind.
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
PRESENT — Determine whether an optional dummy argument is specifiedRESULT = PRESENT(A)
| 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.
|
TRUE if the optional argument A is present, or
FALSE otherwise.
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
PRODUCT — Product of array elementsTRUE.
RESULT = PRODUCT(ARRAY[, MASK])
|
RESULT = PRODUCT(ARRAY, DIM[, MASK])
|
| 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.
|
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.
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
RADIX — Base of a model numberRADIX(X) returns the base of the model representing the entity X.
RESULT = RADIX(X)
| X | Shall be of type INTEGER or REAL
|
INTEGER and of the default
integer kind.
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
RAN — Real pseudo-random numberRAN intrinsic is
provided as an alias for RAND. See RAND for complete
documentation.
RAND — Real pseudo-random numberRAND(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
RANDOM_NUMBER as it implements a superior algorithm.
RESULT = RAND(I)
| I | Shall be a scalar INTEGER of kind 4.
|
REAL type and the default kind.
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
RANDOM_NUMBER — Pseudo-random numberThe runtime-library implements George Marsaglia's KISS (Keep It Simple Stupid) random number generator (RNG). This RNG combines:
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.
RANDOM_NUMBER(HARVEST)
| HARVEST | Shall be a scalar or an array of type REAL.
|
program test_random_number
REAL :: r(5,5)
CALL init_random_seed() ! see example of RANDOM_SEED
CALL RANDOM_NUMBER(r)
end program
RANDOM_SEED — Initialize a pseudo-random number sequenceRANDOM_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 with a varying seed in order to ensure a different random
number sequence for each invocation of the program. Note that setting
any of the seed values to zero should be avoided as it can result in
poor quality random numbers being generated.
CALL RANDOM_SEED([SIZE, PUT, GET])
| 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.
|
subroutine init_random_seed()
use iso_fortran_env, only: int64
implicit none
integer, allocatable :: seed(:)
integer :: i, n, un, istat, dt(8), pid
integer(int64) :: t
call random_seed(size = n)
allocate(seed(n))
! First try if the OS provides a random number generator
open(newunit=un, file="/dev/urandom", access="stream", &
form="unformatted", action="read", status="old", iostat=istat)
if (istat == 0) then
read(un) seed
close(un)
else
! Fallback to XOR:ing the current time and pid. The PID is
! useful in case one launches multiple instances of the same
! program in parallel.
call system_clock(t)
if (t == 0) then
call date_and_time(values=dt)
t = (dt(1) - 1970) * 365_int64 * 24 * 60 * 60 * 1000 &
+ dt(2) * 31_int64 * 24 * 60 * 60 * 1000 &
+ dt(3) * 24_int64 * 60 * 60 * 1000 &
+ dt(5) * 60 * 60 * 1000 &
+ dt(6) * 60 * 1000 + dt(7) * 1000 &
+ dt(8)
end if
pid = getpid()
t = ieor(t, int(pid, kind(t)))
do i = 1, n
seed(i) = lcg(t)
end do
end if
call random_seed(put=seed)
contains
! This simple PRNG might not be good enough for real work, but is
! sufficient for seeding a better PRNG.
function lcg(s)
integer :: lcg
integer(int64) :: s
if (s == 0) then
s = 104729
else
s = mod(s, 4294967296_int64)
end if
s = mod(s * 279470273_int64, 4294967291_int64)
lcg = int(mod(s, int(huge(0), int64)), kind(0))
end function lcg
end subroutine init_random_seed
RANGE — Decimal exponent rangeRANGE(X) returns the decimal exponent range in the model of the
type of X.
RESULT = RANGE(X)
| X | Shall be of type INTEGER, REAL
or COMPLEX.
|
INTEGER and of the default integer
kind.
PRECISION for an example.
RANK — Rank of a data objectRANK(A) returns the rank of a scalar or array data object.
RESULT = RANK(A)
| A | can be of any type
|
INTEGER and of the default integer
kind. For arrays, their rank is returned; for scalars zero is returned.
program test_rank
integer :: a
real, allocatable :: b(:,:)
print *, rank(a), rank(b) ! Prints: 0 2
end program test_rank
REAL — Convert to real typeREAL(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.
RESULT = REAL(A [, KIND])
|
RESULT = REALPART(Z)
|
| A | Shall be INTEGER, REAL, or
COMPLEX.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
REAL variable or array under
the following rules:
REAL(A) is converted to a default real type if A is an
integer or real variable.
REAL(A) is converted to a real type with the kind type parameter
of A if A is a complex variable.
REAL(A, KIND) is converted to a real type with kind type
parameter KIND if A is a complex, integer, or real
variable.
program test_real
complex :: x = (1.0, 2.0)
print *, real(x), real(x,8), realpart(x)
end program test_real
| Name | Argument | Return type | Standard
|
FLOAT(A) | INTEGER(4) | REAL(4) | Fortran 77 and later
|
DFLOAT(A) | INTEGER(4) | REAL(8) | GNU extension
|
SNGL(A) | INTEGER(8) | REAL(4) | Fortran 77 and later
|
RENAME — Rename a fileCHAR(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.
CALL RENAME(PATH1, PATH2 [, STATUS])
|
STATUS = RENAME(PATH1, PATH2)
|
| PATH1 | Shall be of default CHARACTER type.
|
| PATH2 | Shall be of default CHARACTER type.
|
| STATUS | (Optional) Shall be of default INTEGER type.
|
REPEAT — Repeated string concatenationRESULT = REPEAT(STRING, NCOPIES)
| STRING | Shall be scalar and of type CHARACTER.
|
| NCOPIES | Shall be scalar and of type INTEGER.
|
CHARACTER built up from NCOPIES copies
of STRING.
program test_repeat
write(*,*) repeat("x", 5) ! "xxxxx"
end program
RESHAPE — Function to reshape an arrayRESULT = RESHAPE(SOURCE, SHAPE[, PAD, ORDER])
| 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.
|
PROGRAM test_reshape
INTEGER, DIMENSION(4) :: x
WRITE(*,*) SHAPE(x) ! prints "4"
WRITE(*,*) SHAPE(RESHAPE(x, (/2, 2/))) ! prints "2 2"
END PROGRAM
RRSPACING — Reciprocal of the relative spacingRRSPACING(X) returns the reciprocal of the relative spacing of
model numbers near X.
RESULT = RRSPACING(X)
| X | Shall be of type REAL.
|
ABS(FRACTION(X)) * FLOAT(RADIX(X))**DIGITS(X).
RSHIFT — Right shift bitsRSHIFT 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 right end are lost. The fill is arithmetic: the
bits shifted in from the left end are equal to the leftmost bit, which in
two's complement representation is the sign bit.
This function has been superseded by the SHIFTA intrinsic, which
is standard in Fortran 2008 and later.
RESULT = RSHIFT(I, SHIFT)
| I | The type shall be INTEGER.
|
| SHIFT | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
SAME_TYPE_AS — Query dynamic types for equalityRESULT = SAME_TYPE_AS(A, B)
| A | Shall be an object of extensible declared type or
unlimited polymorphic.
|
| B | Shall be an object of extensible declared type or
unlimited polymorphic.
|
SCALE — Scale a real valueSCALE(X,I) returns X * RADIX(X)**I.
RESULT = SCALE(X, I)
| X | The type of the argument shall be a REAL.
|
| I | The type of the argument shall be a INTEGER.
|
X * RADIX(X)**I.
program test_scale
real :: x = 178.1387e-4
integer :: i = 5
print *, scale(x,i), x*radix(x)**i
end program test_scale
SCAN — Scan a string for the presence of a set of charactersIf 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.
RESULT = SCAN(STRING, SET[, BACK [, KIND]])
| 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.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
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
SECNDS — Time functionSECNDS(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.
RESULT = SECNDS (X)
| T | Shall be of type REAL(4).
|
| X | Shall be of type REAL(4).
|
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
SECOND — CPU time functionREAL(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.
CALL SECOND(TIME)
|
TIME = SECOND()
|
| TIME | Shall be of type REAL(4).
|
SELECTED_CHAR_KIND — Choose character kindSELECTED_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, and “ISO_10646”
(Universal Character Set, UCS-4) which is commonly known as Unicode.
RESULT = SELECTED_CHAR_KIND(NAME)
| NAME | Shall be a scalar and of the default character type.
|
program character_kind
use iso_fortran_env
implicit none
integer, parameter :: ascii = selected_char_kind ("ascii")
integer, parameter :: ucs4 = selected_char_kind ('ISO_10646')
character(kind=ascii, len=26) :: alphabet
character(kind=ucs4, len=30) :: hello_world
alphabet = ascii_"abcdefghijklmnopqrstuvwxyz"
hello_world = ucs4_'Hello World and Ni Hao -- ' &
// char (int (z'4F60'), ucs4) &
// char (int (z'597D'), ucs4)
write (*,*) alphabet
open (output_unit, encoding='UTF-8')
write (*,*) trim (hello_world)
end program character_kind
SELECTED_INT_KIND — Choose integer kindSELECTED_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.
RESULT = SELECTED_INT_KIND(R)
| R | Shall be a scalar and of type INTEGER.
|
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
SELECTED_REAL_KIND — Choose real kindSELECTED_REAL_KIND(P,R) returns the kind value of a real data type
with decimal precision of at least P digits, exponent range of
at least R, and with a radix of RADIX.
RADIX Fortran 2008 or later
RESULT = SELECTED_REAL_KIND([P, R, RADIX])
| P | (Optional) shall be a scalar and of type INTEGER.
|
| R | (Optional) shall be a scalar and of type INTEGER.
|
| RADIX | (Optional) shall be a scalar and of type INTEGER.
|
SELECTED_REAL_KIND returns the value of the kind type parameter of
a real data type with decimal precision of at least P digits, a
decimal exponent range of at least R, and with the requested
RADIX. If the RADIX parameter is absent, real kinds with
any radix can be returned. 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
P, but the R and
RADIX requirements can be fulfilled
R, but P and RADIX
are fulfillable
RADIX but not P and R requirementsRADIX and either P or R requirementsRADIX 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
SET_EXPONENT — Set the exponent of the modelSET_EXPONENT(X, I) returns the real number whose fractional part
is that that of X and whose exponent part is I.
RESULT = SET_EXPONENT(X, I)
| X | Shall be of type REAL.
|
| I | Shall be of type INTEGER.
|
FRACTION(X) * RADIX(X)**I.
PROGRAM test_setexp
REAL :: x = 178.1387e-4
INTEGER :: i = 17
PRINT *, SET_EXPONENT(x, i), FRACTION(x) * RADIX(x)**i
END PROGRAM
SHAPE — Determine the shape of an arrayRESULT = SHAPE(SOURCE [, KIND])
| 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.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
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. If KIND is absent, the
return value has the default integer kind otherwise the specified kind.
PROGRAM test_shape
INTEGER, DIMENSION(-1:1, -1:2) :: A
WRITE(*,*) SHAPE(A) ! (/ 3, 4 /)
WRITE(*,*) SIZE(SHAPE(42)) ! (/ /)
END PROGRAM
SHIFTA — Right shift with fillSHIFTA 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 right end are lost. The fill is arithmetic: the
bits shifted in from the left end are equal to the leftmost bit, which in
two's complement representation is the sign bit.
RESULT = SHIFTA(I, SHIFT)
| I | The type shall be INTEGER.
|
| SHIFT | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
SHIFTL — Left shiftSHIFTL 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, and bits shifted in from
the right end are set to 0.
RESULT = SHIFTL(I, SHIFT)
| I | The type shall be INTEGER.
|
| SHIFT | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
SHIFTR — Right shiftSHIFTR 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 right end are lost, and bits shifted in from
the left end are set to 0.
RESULT = SHIFTR(I, SHIFT)
| I | The type shall be INTEGER.
|
| SHIFT | The type shall be INTEGER.
|
INTEGER and of the same kind as
I.
SIGN — Sign copying functionSIGN(A,B) returns the value of A with the sign of B.
RESULT = SIGN(A, B)
| A | Shall be of type INTEGER or REAL
|
| B | Shall be of the same type and kind as A
|
ABS(A), else
it is -ABS(A).
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
| Name | Arguments | Return type | Standard
|
SIGN(A,B) | REAL(4) A, B | REAL(4) | f77, gnu
|
ISIGN(A,B) | INTEGER(4) A, B | INTEGER(4) | f77, gnu
|
DSIGN(A,B) | REAL(8) A, B | REAL(8) | f77, gnu
|
SIGNAL — Signal handling subroutine (or function)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).
CALL SIGNAL(NUMBER, HANDLER [, STATUS])
|
STATUS = SIGNAL(NUMBER, HANDLER)
|
| 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).
|
SIGNAL function returns the value returned by signal(2).
program test_signal
intrinsic signal
external handler_print
call signal (12, handler_print)
call signal (10, 1)
call sleep (30)
end program test_signal
SIN — Sine functionSIN(X) computes the sine of X.
RESULT = SIN(X)
| X | The type shall be REAL or
COMPLEX.
|
program test_sin
real :: x = 0.0
x = sin(x)
end program test_sin
| Name | Argument | Return type | Standard
|
SIN(X) | REAL(4) X | REAL(4) | f77, gnu
|
DSIN(X) | REAL(8) X | REAL(8) | f95, gnu
|
CSIN(X) | COMPLEX(4) X | COMPLEX(4) | f95, gnu
|
ZSIN(X) | COMPLEX(8) X | COMPLEX(8) | f95, gnu
|
CDSIN(X) | COMPLEX(8) X | COMPLEX(8) | f95, gnu
|
SINH — Hyperbolic sine functionSINH(X) computes the hyperbolic sine of X.
RESULT = SINH(X)
| X | The type shall be REAL or COMPLEX.
|
program test_sinh
real(8) :: x = - 1.0_8
x = sinh(x)
end program test_sinh
| Name | Argument | Return type | Standard
|
SINH(X) | REAL(4) X | REAL(4) | Fortran 95 and later
|
DSINH(X) | REAL(8) X | REAL(8) | Fortran 95 and later
|
SIZE — Determine the size of an arrayRESULT = SIZE(ARRAY[, DIM [, KIND]])
| 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.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
PROGRAM test_size
WRITE(*,*) SIZE((/ 1, 2 /)) ! 2
END PROGRAM
SIZEOF — Size in bytes of an expressionSIZEOF(X) calculates the number of bytes of storage the
expression X occupies.
N = SIZEOF(X)
| X | The argument shall be of any type, rank or shape.
|
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 does not account for
the sizes of the data pointed to by these components. If the argument is
polymorphic, the size according to the declared type is returned. The argument
may not be a procedure or procedure pointer.
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.
SLEEP — Sleep for the specified number of secondsCALL SLEEP(SECONDS)
| SECONDS | The type shall be of default INTEGER.
|
program test_sleep
call sleep(5)
end
SPACING — Smallest distance between two numbers of a given typeRESULT = SPACING(X)
| X | Shall be of type REAL.
|
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
SPREAD — Add a dimension to an arrayRESULT = SPREAD(SOURCE, DIM, NCOPIES)
| 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.
|
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
SQRT — Square-root functionSQRT(X) computes the square root of X.
RESULT = SQRT(X)
| X | The type shall be REAL or
COMPLEX.
|
REAL or COMPLEX.
The kind type parameter is the same as X.
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
| Name | Argument | Return type | Standard
|
SQRT(X) | REAL(4) X | REAL(4) | Fortran 95 and later
|
DSQRT(X) | REAL(8) X | REAL(8) | Fortran 95 and later
|
CSQRT(X) | COMPLEX(4) X | COMPLEX(4) | Fortran 95 and later
|
ZSQRT(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension
|
CDSQRT(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension
|
SRAND — Reinitialize the random number generatorSRAND 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.
CALL SRAND(SEED)
| SEED | Shall be a scalar INTEGER(kind=4).
|
RAND and IRAND for examples.
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.
STAT — Get file statusThe 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.
CALL STAT(NAME, VALUES [, STATUS])
|
STATUS = STAT(NAME, VALUES)
|
| 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.
|
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
STORAGE_SIZE — Storage size in bitsRESULT = STORAGE_SIZE(A [, KIND])
| A | Shall be a scalar or array of any type.
|
| KIND | (Optional) shall be a scalar integer constant expression.
|
SUM — Sum of array elementsTRUE.
RESULT = SUM(ARRAY[, MASK])
|
RESULT = SUM(ARRAY, DIM[, MASK])
|
| 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.
|
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.
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
SYMLNK — Create a symbolic linkCHAR(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.
CALL SYMLNK(PATH1, PATH2 [, STATUS])
|
STATUS = SYMLNK(PATH1, PATH2)
|
| PATH1 | Shall be of default CHARACTER type.
|
| PATH2 | Shall be of default CHARACTER type.
|
| STATUS | (Optional) Shall be of default INTEGER type.
|
SYSTEM — Execute a shell commandsystem(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.
Note that the system function need not be thread-safe. It is
the responsibility of the user to ensure that system is not
called concurrently.
CALL SYSTEM(COMMAND [, STATUS])
|
STATUS = SYSTEM(COMMAND)
|
| COMMAND | Shall be of default CHARACTER type.
|
| STATUS | (Optional) Shall be of default INTEGER type.
|
SYSTEM_CLOCK — Time functionCOUNT_RATE is system dependent and can vary depending on the
kind of the arguments. For kind=4 arguments, COUNT
represents milliseconds, while for kind=8 arguments, COUNT
typically represents micro- or nanoseconds depending on resolution of
the underlying platform clock. COUNT_MAX usually equals
HUGE(COUNT_MAX). Note that the millisecond resolution of the
kind=4 version implies that the COUNT will wrap around in
roughly 25 days. In order to avoid issues with the wrap around and for
more precise timing, please use the kind=8 version.
If there is no clock, or querying the clock fails, COUNT is set
to -HUGE(COUNT), and COUNT_RATE and COUNT_MAX are
set to zero.
When running on a platform using the GNU C library (glibc) version
2.16 or older, or a derivative thereof, the high resolution monotonic
clock is available only when linking with the rt library. This
can be done explicitly by adding the -lrt flag when linking the
application, but is also done implicitly when using OpenMP.
On the Windows platform, the version with kind=4 arguments uses
the GetTickCount function, whereas the kind=8 version
uses QueryPerformanceCounter and
QueryPerformanceCounterFrequency. For more information, and
potential caveats, please see the platform documentation.
CALL SYSTEM_CLOCK([COUNT, COUNT_RATE, COUNT_MAX])
| COUNT | (Optional) shall be a scalar of type
INTEGER with INTENT(OUT).
|
| COUNT_RATE | (Optional) shall be a scalar of type
INTEGER with INTENT(OUT).
|
| COUNT_MAX | (Optional) shall be a scalar of type
INTEGER with INTENT(OUT).
|
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
TAN — Tangent functionTAN(X) computes the tangent of X.
RESULT = TAN(X)
| X | The type shall be REAL or COMPLEX.
|
program test_tan
real(8) :: x = 0.165_8
x = tan(x)
end program test_tan
| Name | Argument | Return type | Standard
|
TAN(X) | REAL(4) X | REAL(4) | Fortran 95 and later
|
DTAN(X) | REAL(8) X | REAL(8) | Fortran 95 and later
|
TANH — Hyperbolic tangent functionTANH(X) computes the hyperbolic tangent of X.
X = TANH(X)
| X | The type shall be REAL or COMPLEX.
|
REAL, the return value lies in the range
- 1 \leq tanh(x) \leq 1 .
program test_tanh
real(8) :: x = 2.1_8
x = tanh(x)
end program test_tanh
| Name | Argument | Return type | Standard
|
TANH(X) | REAL(4) X | REAL(4) | Fortran 95 and later
|
DTANH(X) | REAL(8) X | REAL(8) | Fortran 95 and later
|
THIS_IMAGE — Function that returns the cosubscript index of this imageRESULT = THIS_IMAGE()
|
RESULT = THIS_IMAGE(COARRAY [, DIM])
|
| COARRAY | Coarray of any type (optional; if DIM
present, required).
|
| DIM | default integer scalar (optional). If present,
DIM shall be between one and the corank of COARRAY.
|
THIS_IMAGE(COARRAY).
INTEGER :: value[*]
INTEGER :: i
value = THIS_IMAGE()
SYNC ALL
IF (THIS_IMAGE() == 1) THEN
DO i = 1, NUM_IMAGES()
WRITE(*,'(2(a,i0))') 'value[', i, '] is ', value[i]
END DO
END IF
TIME — Time functiontime(3) in the C standard library). 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 TIME8, for information on a similar intrinsic that might be
portable to more GNU Fortran implementations, though to fewer Fortran
compilers.
RESULT = TIME()
INTEGER(4).
TIME8 — Time function (64-bit)time(3) in the C standard library). 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.
RESULT = TIME8()
INTEGER(8).
TINY — Smallest positive number of a real kindTINY(X) returns the smallest positive (non zero) number
in the model of the type of X.
RESULT = TINY(X)
| X | Shall be of type REAL.
|
HUGE for an example.
TRAILZ — Number of trailing zero bits of an integerTRAILZ returns the number of trailing zero bits of an integer.
RESULT = TRAILZ(I)
| I | Shall be of type INTEGER.
|
INTEGER.
If all the bits of I are zero, the result value is BIT_SIZE(I).
PROGRAM test_trailz
WRITE (*,*) TRAILZ(8) ! prints 3
END PROGRAM
TRANSFER — Transfer bit patternsThis is approximately equivalent to the C concept of casting one
type to another.
RESULT = TRANSFER(SOURCE, MOLD[, SIZE])
| 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.
|
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.
PROGRAM test_transfer
integer :: x = 2143289344
print *, transfer(x, 1.0) ! prints "NaN" on i686
END PROGRAM
TRANSPOSE — Transpose an array of rank twoMATRIX(j, i), for all i, j.
RESULT = TRANSPOSE(MATRIX)
| MATRIX | Shall be an array of any type and have a rank of two.
|
(/ m, n /) if MATRIX has shape (/ n, m /).
TRIM — Remove trailing blank characters of a stringRESULT = TRIM(STRING)
| STRING | Shall be a scalar of type CHARACTER.
|
CHARACTER which length is that of STRING
less the number of trailing blanks.
PROGRAM test_trim
CHARACTER(len=10), PARAMETER :: s = "GFORTRAN "
WRITE(*,*) LEN(s), LEN(TRIM(s)) ! "10 8", with/without trailing blanks
END PROGRAM
TTYNAM — Get the name of a terminal device.ttyname(3).
This intrinsic is provided in both subroutine and function forms;
however, only one form can be used in any given program unit.
CALL TTYNAM(UNIT, NAME)
|
NAME = TTYNAM(UNIT)
|
| UNIT | Shall be a scalar INTEGER.
|
| NAME | Shall be of type CHARACTER.
|
PROGRAM test_ttynam
INTEGER :: unit
DO unit = 1, 10
IF (isatty(unit=unit)) write(*,*) ttynam(unit)
END DO
END PROGRAM
UBOUND — Upper dimension bounds of an arrayRESULT = UBOUND(ARRAY [, DIM [, KIND]])
| 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.
|
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.
UCOBOUND — Upper codimension bounds of an arrayRESULT = UCOBOUND(COARRAY [, DIM [, KIND]])
| ARRAY | Shall be an coarray, of any type.
|
| DIM | (Optional) Shall be a scalar INTEGER.
|
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result.
|
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 cobounds of
COARRAY. If DIM is present, the result is a scalar
corresponding to the lower cobound of the array along that codimension.
UMASK — Set the file creation maskumask(2).
CALL UMASK(MASK [, OLD])
|
OLD = UMASK(MASK)
|
| MASK | Shall be a scalar of type INTEGER.
|
| OLD | (Optional) Shall be a scalar of type
INTEGER.
|
UNLINK — Remove a file from the file systemCHAR(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.
CALL UNLINK(PATH [, STATUS])
|
STATUS = UNLINK(PATH)
|
| PATH | Shall be of default CHARACTER type.
|
| STATUS | (Optional) Shall be of default INTEGER type.
|
UNPACK — Unpack an array of rank one into an arrayRESULT = UNPACK(VECTOR, MASK, FIELD)
| 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.
|
TRUE elements
of MASK replaced by values from VECTOR in array element order.
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
VERIFY — Scan a string for characters not a given setIf 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 STRING are found in
SET, the result is zero.
RESULT = VERIFY(STRING, SET[, BACK [, KIND]])
| 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.
|
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
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
XOR — Bitwise logical exclusive ORThis intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. For integer arguments, programmers should consider
the use of the IEOR intrinsic and for logical arguments the
.NEQV. operator, which are both defined by the Fortran standard.
RESULT = XOR(I, J)
| 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.
|
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.
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
ISO_FORTRAN_ENVThe ISO_FORTRAN_ENV module provides the following scalar default-integer
named constants:
ATOMIC_INT_KIND:ATOMIC_LOGICAL_KIND:CHARACTER_KINDS:CHARACTER type. (Fortran 2008 or later.)
CHARACTER_STORAGE_SIZE:ERROR_UNIT:FILE_STORAGE_SIZE:INPUT_UNIT:*) in READ statement.
INT8, INT16, INT32, INT64:INTEGER_KINDS:INTEGER type. (Fortran 2008 or later.)
IOSTAT_END:IOSTAT= specifier of
an input/output statement if an end-of-file condition occurred.
IOSTAT_EOR:IOSTAT= specifier of
an input/output statement if an end-of-record condition occurred.
IOSTAT_INQUIRE_INTERNAL_UNIT:INQUIRE for the
IOSTAT= specifier to denote an that a unit number identifies an
internal unit. (Fortran 2008 or later.)
NUMERIC_STORAGE_SIZE:LOGICAL_KINDS:LOGICAL type. (Fortran 2008 or later.)
OUTPUT_UNIT:*) in WRITE statement.
REAL32, REAL64, REAL128:REAL_KINDS:REAL type. (Fortran 2008 or later.)
STAT_LOCKED:LOCK to
denote that the lock variable is locked by the executing image. (Fortran 2008
or later.)
STAT_LOCKED_OTHER_IMAGE:UNLOCK to
denote that the lock variable is locked by another image. (Fortran 2008 or
later.)
STAT_STOPPED_IMAGE:STAT_UNLOCKED:UNLOCK to
denote that the lock variable is unlocked. (Fortran 2008 or later.)
The module provides the following derived type:
LOCK_TYPE:LOCK and
UNLOCK statement. A variable of its type has to be always declared
as coarray and may not appear in a variable-definition context.
(Fortran 2008 or later.)
The module also provides the following intrinsic procedures: COMPILER_OPTIONS and COMPILER_VERSION.
ISO_C_BINDINGThe following intrinsic procedures are provided by the module; their definition can be found in the section Intrinsic Procedures of this manual.
C_ASSOCIATEDC_F_POINTERC_F_PROCPOINTERC_FUNLOCC_LOCC_SIZEOFThe 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 and C_PTRDIFF_T of TS 29113, 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.
Furthermore, if __float128 is supported in C, the named constants
C_FLOAT128, C_FLOAT128_COMPLEX are defined.
| Fortran Type | Named constant | C type | Extension
|
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
| |
INTEGER | C_PTRDIFF_T | intptr_t | TS 29113
|
REAL | C_FLOAT | float
| |
REAL | C_DOUBLE | double
| |
REAL | C_LONG_DOUBLE | long double
| |
REAL | C_FLOAT128 | __float128 | Ext.
|
COMPLEX | C_FLOAT_COMPLEX | float _Complex
| |
COMPLEX | C_DOUBLE_COMPLEX | double _Complex
| |
COMPLEX | C_LONG_DOUBLE_COMPLEX | long double _Complex
| |
REAL | C_FLOAT128_COMPLEX | __float128 _Complex | Ext.
|
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'
|
Moreover, the following two named constants are defined:
| Name | Type
|
C_NULL_PTR | C_PTR
|
C_NULL_FUNPTR | C_FUNPTR
|
Both are equivalent to the value NULL in C.
OMP_LIB and OMP_LIB_KINDSThe 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 Introduction manual,
the named constants defined in the modules are listed
below.
For details refer to the actual OpenMP Application Program Interface v4.0.
OMP_LIB_KINDS provides the following scalar default-integer
named constants:
omp_lock_kindomp_nest_lock_kindomp_proc_bind_kindomp_sched_kindOMP_LIB provides the scalar default-integer
named constant openmp_version with a value of the form
yyyymm, where yyyy is the year and mm the month
of the OpenMP version; for OpenMP v4.0 the value is 201307.
The following scalar integer named constants of the
kind omp_sched_kind:
omp_sched_staticomp_sched_dynamicomp_sched_guidedomp_sched_autoAnd the following scalar integer named constants of the
kind omp_proc_bind_kind:
omp_proc_bind_falseomp_proc_bind_trueomp_proc_bind_masteromp_proc_bind_closeomp_proc_bind_spreadFree 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 will eventually get around to the things here, but they are also things doable by someone who is willing and able.
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):
The following people have contributed bug reports, smaller or larger patches, and much needed feedback and encouragement for the GNU Fortran project:
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.
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.
Copyright © 2007 Free Software Foundation, Inc. http://fsf.org/
Everyone is permitted to copy and distribute verbatim copies of this
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Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.
You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.
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You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.
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A contributor's “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.
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If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.
If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.
A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.
If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other 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.
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 single combined work, and to convey the resulting work. The terms 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.
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.
Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.
If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.
Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.
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 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
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.
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.
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.
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
http://fsf.org/
Everyone is permitted to copy and distribute verbatim copies
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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.
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.
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A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.
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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.
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.
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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.
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:
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 other section titles.
You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, 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 Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.
You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”
You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and 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.
A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.
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.
You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.
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Copyright © 1994 Free Software Foundation, Inc.
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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.
A-predicate=answer: Preprocessing OptionsApredicate=answer: Preprocessing Optionsbackslash: Fortran Dialect OptionsC: Preprocessing OptionsCC: Preprocessing Optionscpp: Preprocessing OptionsdD: Preprocessing OptionsdI: Preprocessing OptionsdM: Preprocessing OptionsdN: Preprocessing OptionsDname: Preprocessing OptionsDname=definition: Preprocessing OptionsdU: Preprocessing Optionsfaggressive-function-elimination: Code Gen Optionsfalign-commons: Code Gen Optionsfall-intrinsics: Fortran Dialect Optionsfblas-matmul-limit: Code Gen Optionsfbounds-check: Code Gen Optionsfcheck: Code Gen Optionsfcheck-array-temporaries: Code Gen Optionsfcoarray: Code Gen Optionsfconvert=conversion: Runtime Optionsfcray-pointer: Fortran Dialect Optionsfd-lines-as-code: Fortran Dialect Optionsfd-lines-as-comments: Fortran Dialect Optionsfdefault-double-8: Fortran Dialect Optionsfdefault-integer-8: Fortran Dialect Optionsfdefault-real-8: Fortran Dialect Optionsfdollar-ok: Fortran Dialect Optionsfdump-fortran-optimized: Debugging Optionsfdump-fortran-original: Debugging Optionsfdump-parse-tree: Debugging Optionsfexternal-blas: Code Gen Optionsff2c: Code Gen Optionsffixed-line-length-n: Fortran Dialect Optionsffpe-summary=list: Debugging Optionsffpe-trap=list: Debugging Optionsffree-form: Fortran Dialect Optionsffree-line-length-n: Fortran Dialect Optionsfimplicit-none: Fortran Dialect Optionsfinit-character: Code Gen Optionsfinit-integer: Code Gen Optionsfinit-local-zero: Code Gen Optionsfinit-logical: Code Gen Optionsfinit-real: Code Gen Optionsfinteger-4-integer-8: Fortran Dialect Optionsfintrinsic-modules-path dir: Directory Optionsfmax-array-constructor: Code Gen Optionsfmax-errors=n: Error and Warning Optionsfmax-identifier-length=n: Fortran Dialect Optionsfmax-stack-var-size: Code Gen Optionsfmax-subrecord-length=length: Runtime Optionsfmodule-private: Fortran Dialect Optionsfno-automatic: Code Gen Optionsfno-backtrace: Debugging Optionsfno-fixed-form: Fortran Dialect Optionsfno-protect-parens: Code Gen Optionsfno-underscoring: Code Gen Optionsfopenmp: Fortran Dialect Optionsfpack-derived: Code Gen Optionsfpp: Preprocessing Optionsfrange-check: Fortran Dialect Optionsfreal-4-real-10: Fortran Dialect Optionsfreal-4-real-16: Fortran Dialect Optionsfreal-4-real-8: Fortran Dialect Optionsfreal-8-real-10: Fortran Dialect Optionsfreal-8-real-16: Fortran Dialect Optionsfreal-8-real-4: Fortran Dialect Optionsfrealloc-lhs: Code Gen Optionsfrecord-marker=length: Runtime Optionsfrecursive: Code Gen Optionsfrepack-arrays: Code Gen Optionsfrontend-optimize: Code Gen Optionsfsecond-underscore: Code Gen Optionsfshort-enums: Fortran 2003 statusfshort-enums: Code Gen Optionsfsign-zero: Runtime Optionsfstack-arrays: Code Gen Optionsfsyntax-only: Error and Warning Optionsfworking-directory: Preprocessing OptionsH: Preprocessing OptionsIdir: Directory Optionsidirafter dir: Preprocessing Optionsimultilib dir: Preprocessing Optionsiprefix prefix: Preprocessing Optionsiquote dir: Preprocessing Optionsisysroot dir: Preprocessing Optionsisystem dir: Preprocessing OptionsJdir: Directory OptionsMdir: Directory Optionsnostdinc: Preprocessing OptionsP: Preprocessing Optionspedantic: Error and Warning Optionspedantic-errors: Error and Warning Optionsstatic-libgfortran: Link Optionsstd=std option: Fortran Dialect OptionsUname: Preprocessing Optionsundef: Preprocessing OptionsWaliasing: Error and Warning OptionsWalign-commons: Error and Warning OptionsWall: Error and Warning OptionsWampersand: Error and Warning OptionsWarray-temporaries: Error and Warning OptionsWc-binding-type: Error and Warning OptionsWcharacter-truncation: Error and Warning OptionsWcompare-reals: Error and Warning OptionsWconversion: Error and Warning OptionsWconversion-extra: Error and Warning OptionsWerror: Error and Warning OptionsWextra: Error and Warning OptionsWfunction-elimination: Error and Warning OptionsWimplicit-interface: Error and Warning OptionsWimplicit-procedure: Error and Warning OptionsWintrinsic-shadow: Error and Warning OptionsWintrinsics-std: Error and Warning OptionsWline-truncation: Error and Warning OptionsWreal-q-constant: Error and Warning OptionsWrealloc-lhs: Error and Warning OptionsWrealloc-lhs-all: Error and Warning OptionsWsurprising: Error and Warning OptionsWtabs: Error and Warning OptionsWtargt-lifetime: Error and Warning OptionsWunderflow: Error and Warning OptionsWunused-dummy-argument: Error and Warning OptionsWunused-parameter: Error and Warning OptionsWzerotrip: Error and Warning Options$: Fortran Dialect Options%LOC: Argument list functions%REF: Argument list functions%VAL: Argument list functions&: Error and Warning Options[...]: Fortran 2003 status_gfortran_set_args: _gfortran_set_args_gfortran_set_convert: _gfortran_set_convert_gfortran_set_fpe: _gfortran_set_fpe_gfortran_set_max_subrecord_length: _gfortran_set_max_subrecord_length_gfortran_set_options: _gfortran_set_options_gfortran_set_record_marker: _gfortran_set_record_markerABORT: ABORTABS: ABSACCESS: ACCESSACCESS='STREAM' I/O: Fortran 2003 statusACHAR: ACHARACOS: ACOSACOSH: ACOSHADJUSTL: ADJUSTLADJUSTR: ADJUSTRAIMAG: AIMAGAINT: AINTALARM: ALARMALGAMA: LOG_GAMMACOMMON blocks: Code Gen OptionsCOMMON blocks: Error and Warning OptionsALL: ALLALLOCATABLE components of derived types: Fortran 2003 statusALLOCATABLE dummy arguments: Fortran 2003 statusALLOCATABLE function results: Fortran 2003 statusALLOCATED: ALLOCATEDALOG: LOGALOG10: LOG10AMAX0: MAXAMAX1: MAXAMIN0: MINAMIN1: MINAMOD: MODAND: ANDANINT: ANINTANY: ANYASIN: ASINASINH: ASINHASSOCIATED: ASSOCIATEDATAN: ATANATAN2: ATAN2ATANH: ATANHATOMIC_DEFINE: ATOMIC_DEFINEATOMIC_REF: ATOMIC_REFBACKTRACE: BACKTRACEBESJ0: BESSEL_J0BESJ1: BESSEL_J1BESJN: BESSEL_JNBESSEL_J0: BESSEL_J0BESSEL_J1: BESSEL_J1BESSEL_JN: BESSEL_JNBESSEL_Y0: BESSEL_Y0BESSEL_Y1: BESSEL_Y1BESSEL_YN: BESSEL_YNBESY0: BESSEL_Y0BESY1: BESSEL_Y1BESYN: BESSEL_YNBGE: BGEBGT: BGTBIT_SIZE: BIT_SIZEBLE: BLEBLT: BLTBTEST: BTESTC_ASSOCIATED: C_ASSOCIATEDC_F_POINTER: C_F_POINTERC_F_PROCPOINTER: C_F_PROCPOINTERC_FUNLOC: C_FUNLOCC_LOC: C_LOCC_SIZEOF: C_SIZEOFCABS: ABSCCOS: COSCDABS: ABSCDCOS: COSCDEXP: EXPCDLOG: LOGCDSIN: SINCDSQRT: SQRTCEILING: CEILINGCEXP: EXPCHAR: CHARCHDIR: CHDIRCHMOD: CHMODCLOG: LOGCMPLX: CMPLXIMAGE_INDEX: IMAGE_INDEXNUM_IMAGES: NUM_IMAGESTHIS_IMAGE: THIS_IMAGECOMMAND_ARGUMENT_COUNT: COMMAND_ARGUMENT_COUNTCOMMON: Volatile COMMON blocksCOMPILER_OPTIONS: COMPILER_OPTIONSCOMPILER_VERSION: COMPILER_VERSIONCOMPLEX: COMPLEXCONJG: CONJGCONVERT specifier: CONVERT specifierCOS: COSCOSH: COSHCOUNT: COUNTCPU_TIME: CPU_TIMECSHIFT: CSHIFTCSIN: SINCSQRT: SQRTCTIME: CTIMEDABS: ABSDACOS: ACOSDACOSH: ACOSHDASIN: ASINDASINH: ASINHDATAN: ATANDATAN2: ATAN2DATANH: ATANHDATE_AND_TIME: DATE_AND_TIMEDBESJ0: BESSEL_J0DBESJ1: BESSEL_J1DBESJN: BESSEL_JNDBESY0: BESSEL_Y0DBESY1: BESSEL_Y1DBESYN: BESSEL_YNDBLE: DBLEDCMPLX: DCMPLXDCONJG: CONJGDCOS: COSDCOSH: COSHDDIM: DIMDECODE: ENCODE and DECODE statementsDEXP: EXPDFLOAT: REALDGAMMA: GAMMADIGITS: DIGITSDIM: DIMDIMAG: AIMAGDINT: AINTINCLUDE: Directory OptionsDLGAMA: LOG_GAMMADLOG: LOGDLOG10: LOG10DMAX1: MAXDMIN1: MINDMOD: MODDNINT: ANINTDOT_PRODUCT: DOT_PRODUCTDPROD: DPRODDREAL: DREALDSHIFTL: DSHIFTLDSHIFTR: DSHIFTRDSIGN: SIGNDSIN: SINDSINH: SINHDSQRT: SQRTDTAN: TANDTANH: TANHDTIME: DTIMEENCODE: ENCODE and DECODE statementsENUM statement: Fortran 2003 statusENUMERATOR statement: Fortran 2003 statusEOSHIFT: EOSHIFTEPSILON: EPSILONERF: ERFERFC: ERFCERFC_SCALED: ERFC_SCALEDETIME: ETIMEEXECUTE_COMMAND_LINE: EXECUTE_COMMAND_LINEEXIT: EXITEXP: EXPEXPONENT: EXPONENTEXTENDS_TYPE_OF: EXTENDS_TYPE_OFFDATE: FDATEFGET: FGETFGETC: FGETCFLOAT: REALFLOOR: FLOORFLUSH: FLUSHFLUSH statement: Fortran 2003 statusFNUM: FNUMFORMAT: Variable FORMAT expressionsFPUT: FPUTFPUTC: FPUTCFRACTION: FRACTIONFREE: FREEFSEEK: FSEEKFSTAT: FSTATFTELL: FTELLGAMMA: GAMMAGERROR: GERRORGET_COMMAND: GET_COMMANDGET_COMMAND_ARGUMENT: GET_COMMAND_ARGUMENTGET_ENVIRONMENT_VARIABLE: GET_ENVIRONMENT_VARIABLEGETARG: GETARGGETCWD: GETCWDGETENV: GETENVGETGID: GETGIDGETLOG: GETLOGGETPID: GETPIDGETUID: GETUIDGMTIME: GMTIMEHOSTNM: HOSTNMHUGE: HUGEHYPOT: HYPOTIABS: ABSIACHAR: IACHARIALL: IALLIAND: IANDIANY: IANYIARGC: IARGCIBCLR: IBCLRIBITS: IBITSIBSET: IBSETICHAR: ICHARIDATE: IDATEIDIM: DIMIDINT: INTIDNINT: NINTIEOR: IEORIERRNO: IERRNOIFIX: INTIMAG: AIMAGIMAGE_INDEX: IMAGE_INDEXIMAGPART: AIMAGIMPORT statement: Fortran 2003 statusINCLUDE directive: Directory OptionsINDEX: INDEX intrinsicINT: INTINT2: INT2INT8: INT8IOMSG= specifier: Fortran 2003 statusIOR: IORIOSTAT, end of file: IS_IOSTAT_ENDIOSTAT, end of record: IS_IOSTAT_EORIPARITY: IPARITYIRAND: IRANDIS_IOSTAT_END: IS_IOSTAT_ENDIS_IOSTAT_EOR: IS_IOSTAT_EORISATTY: ISATTYISHFT: ISHFTISHFTC: ISHFTCISIGN: SIGNISNAN: ISNANISO_FORTRAN_ENV statement: Fortran 2003 statusITIME: ITIMEKILL: KILLKIND: KINDLBOUND: LBOUNDLCOBOUND: LCOBOUNDLEADZ: LEADZLEN: LENLEN_TRIM: LEN_TRIMLGAMMA: LOG_GAMMALGE: LGELGT: LGTLINK: LINKLLE: LLELLT: LLTLNBLNK: LNBLNKLOC: LOCLOG: LOGLOG10: LOG10LOG_GAMMA: LOG_GAMMALOGICAL: LOGICALLONG: LONGLSHIFT: LSHIFTLSTAT: LSTATLTIME: LTIMEMALLOC: MALLOCMASKL: MASKLMASKR: MASKRMATMUL: MATMULMAX: MAXMAX0: MAXMAX1: MAXMAXEXPONENT: MAXEXPONENTMAXLOC: MAXLOCMAXVAL: MAXVALMCLOCK: MCLOCKMCLOCK8: MCLOCK8MERGE: MERGEMERGE_BITS: MERGE_BITSMIN: MINMIN0: MINMIN1: MINMINEXPONENT: MINEXPONENTMINLOC: MINLOCMINVAL: MINVALMOD: MODMODULO: MODULOMOVE_ALLOC: MOVE_ALLOCMVBITS: MVBITSNEAREST: NEARESTNEW_LINE: NEW_LINENINT: NINTNORM2: NORM2NOT: NOTNULL: NULLNUM_IMAGES: NUM_IMAGESOR: ORPACK: PACKPARITY: PARITYPERROR: PERRORPOPCNT: POPCNTPOPPAR: POPPARPRECISION: PRECISIONPRESENT: PRESENTPRODUCT: PRODUCTPROTECTED statement: Fortran 2003 statusQ exponent-letter: <code>Q</code> exponent-letterRADIX: RADIXRAN: RANRAND: RANDRANDOM_NUMBER: RANDOM_NUMBERRANDOM_SEED: RANDOM_SEEDRANGE: RANGERANK: RANKREAL: REALREALPART: REALRECORD: STRUCTURE and RECORDRENAME: RENAMEREPEAT: REPEATRESHAPE: RESHAPERRSPACING: RRSPACINGRSHIFT: RSHIFTSAME_TYPE_AS: SAME_TYPE_ASSAVE statement: Code Gen OptionsSCALE: SCALESCAN: SCANSECNDS: SECNDSSECOND: SECONDSELECTED_CHAR_KIND: SELECTED_CHAR_KINDSELECTED_INT_KIND: SELECTED_INT_KINDSELECTED_REAL_KIND: SELECTED_REAL_KINDSET_EXPONENT: SET_EXPONENTSHAPE: SHAPESHIFTA: SHIFTASHIFTL: SHIFTLSHIFTR: SHIFTRSHORT: INT2SIGN: SIGNSIGNAL: SIGNALSIN: SINSINH: SINHSIZE: SIZESIZEOF: SIZEOFSLEEP: SLEEPSNGL: REALSPACING: SPACINGSPREAD: SPREADSQRT: SQRTSRAND: SRANDSTAT: STATENUM: Fortran 2003 statusENUMERATOR: Fortran 2003 statusFLUSH: Fortran 2003 statusIMPORT: Fortran 2003 statusISO_FORTRAN_ENV: Fortran 2003 statusPROTECTED: Fortran 2003 statusSAVE: Code Gen OptionsUSE, INTRINSIC: Fortran 2003 statusVALUE: Fortran 2003 statusVOLATILE: Fortran 2003 statusSTORAGE_SIZE: STORAGE_SIZESTREAM I/O: Fortran 2003 statusSTRUCTURE: STRUCTURE and RECORDSUM: SUMSYMLNK: SYMLNKSYSTEM: SYSTEMSYSTEM_CLOCK: SYSTEM_CLOCKTAN: TANTANH: TANHTHIS_IMAGE: THIS_IMAGETIME: TIMETIME8: TIME8TINY: TINYTRAILZ: TRAILZTRANSFER: TRANSFERTRANSPOSE: TRANSPOSETRIM: TRIMTTYNAM: TTYNAMUBOUND: UBOUNDUCOBOUND: UCOBOUNDUMASK: UMASKUNLINK: UNLINKUNPACK: UNPACKUSE, INTRINSIC statement: Fortran 2003 statusVALUE statement: Fortran 2003 statusVERIFY: VERIFYVOLATILE: Volatile COMMON blocksVOLATILE statement: Fortran 2003 statusCOMMON blocks: Error and Warning Optionsq exponent-letter: Error and Warning OptionsXOR: XORZABS: ABSZCOS: COSZEXP: EXPZLOG: LOGZSIN: SINZSQRT: SQRT