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Fortran Standard Library

The Fortran Standard, as published by the ISO, does not have a standard library, like other programming languages. The Fortran Standard Library (stdlib) is a community-driven de facto standard library currently in development that contains additional algorithms, data structures, as well as math and utility routines for Fortran 2008 and newer (table 1).

Module	Description
stdlib_ansi	Terminal color and style escape sequences
stdlib_array	Index manipulation and array handling tasks
stdlib_ascii	Handling of intrinsic character variables and constants
stdlib_bitsets	Zero-based bitsets of size up to huge(0_int32)
stdlib_error	Catching and handling errors
stdlib_hash_32bit	Hash functions and scalar hashes (32-bit)
stdlib_hash_64bit	Hash functions and scalar hashes (64-bit)
stdlib_hashmap_wrapper	Hash map wrapper procedures
stdlib_hashmaps	Hash maps
stdlib_io	File handling
stdlib_io_npy	NPY file handling
stdlib_kinds	Additional kind declarations
stdlib_linalg	Various linear algebra procedures
stdlib_logger	Logging types and procedures
stdlib_math	Various math procedures
stdlib_optval	Fallback values for optional procedure arguments
stdlib_quadrature	Gaussian approximations
stdlib_random	Random numbers
stdlib_selection	Array element selections
stdlib_sorting	Sorting algorithms
stdlib_specialfunctions	Legendre functions
stdlib_specialfunctions_gamma	Gamma functions
stdlib_stats	Various statistical methods
stdlib_stats_distribution_exponential	Exponential distribution functions
stdlib_stats_distribution_normal	Normal distribution functions
stdlib_stats_distribution_uniform	Uniform distribution functions
stdlib_string_type	String type that holds an arbitrary sequence of characters
stdlib_stringlist_type	String list implementation
stdlib_strings	Basic string handling routines
stdlib_version	Version information on stdlib

Tab. 1: Modules of the Fortran Standard Library

Installation

The library requires a Fortran 2008 compliant compiler and a build automation tool like fpm, make, or CMake:

$ git clone https://github.com/fortran-lang/fpm
$ git checkout stdlib-fpm
$ fpm build --profile release

The static library libstdlib.a and the necessary module files are written to build/<compiler>/stdlib/. To include stdlib as a dependency to a fpm project, simply add the following entry to your fpm.toml:

[dependencies]
stdlib = { git="https://github.com/fortran-lang/stdlib", branch="stdlib-fpm" }

stdlib_logger

The Fortran Standard Library provides a basic logger class to output messages to console and file:

! log.f90
program main
    use, intrinsic :: iso_fortran_env, stderr => error_unit
    use :: stdlib_logger, logger => global_logger
    implicit none
    integer :: fu, stat

    call logger%configure(level=ALL_LEVEL)
    call logger%add_log_unit(stderr, stat=stat)
    call logger%add_log_file('log.txt', fu, stat=stat)

    call logger%log_error(message   = 'Example error log message', &
                          module    = 'N/A', &
                          procedure = 'MAIN', &
                          stat      = 0, &
                          errmsg    = 'error message')

    call logger%log_message('Message printed irrespective of the level')

    call logger%log_debug('Debug message')
    call logger%log_information('Information message')
    call logger%log_warning('Warning message')
    call logger%log_io_error('I/O error message')

    call logger%configure(level=NONE_LEVEL)
    call logger%log_error('Error message (not printed)')
end program main

Link the example program against libstdlib.a and set the include search path -I the the directory containing the module files:

$ gfortran14 -I./build/gfortran/stdlib/ -o log log.f90 ./build/gfortran/stdlib/libstdlib.a

The log messages are printed to standard error and to file log.txt:

$ ./log
2021-10-04 23:04:46.090: N/A % MAIN: ERROR: Example error log message
With stat = 0
With errmsg = "error message"
2021-10-04 23:04:46.091: Message printed irrespective of the level
2021-10-04 23:04:46.091: DEBUG: Debug message
2021-10-04 23:04:46.091: INFO: Information message
2021-10-04 23:04:46.091: WARN: Warning message
2021-10-04 23:04:46.091: I/O ERROR: I/O error message

Similar Fortran Libraries

• flib: Fortran library of useful modules and procedures
• ForUtils: Package of Fortran 2003/2008 utility classes and convenience functions (arrays, file I/O, INI files, ranges, strings, …)
• Fortran-Library: mathematical and chemical routines, e. g., transformations, clustering, statistics, nonlinear optimisation
• Fortran General Library (FGL): Includes logging, exception handling, hash and list data structures, sorting, strings, JSON serialisation
• Fortran Utilities: Various Fortran utilities that can be included into any Fortran program (types, constants, sorting, meshes, cubic splines, PPM images, HDF5)
• fortranlib: Collection of algebra, array, I/O, probability density function, and vector routines
• Futility: Open-source utility package by University of Michigan and Oak Ridge National Laboratory (language extensions, file I/O, math, geometry, sorting, …)
• General-Purpose Fortran Repository: Libraries and modules for command-line parsing, string operations, numeric expression parsing, pixel graphics, message handling, POSIX, regular expressions, SQLite

References

• Fortran Standard Library: Official GitHub repository
• Fortran Standard Library documentation

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