___________                         .__   
\_   _____/__________  _____ _____  |  |   
 |    __)/  _ \_  __ \/     \\__  \ |  |   
 |     \(  <_> )  | \/  Y Y  \/ __ \|  |__ 
 \___  / \____/|__|  |__|_|  (____  /____/
     \/                    \/     \/          

Formal: Fortran mimetic abstraction language

Towards a formally verifiable, tensor-calculus langauge embedded in Fortran 2028.

Examples

See this repository's example subdirectory for demonstrations of how to use Formal. For usage information for each example, execute something like:

fpm run --example <base-name> -- --help

where base-name is the portion of an example file name preceding the .F90 or .f90 extension. To save typing in a terminal window, set the example directory as your present working directory before issuing the above fpm run command. Then use tab completion to enter enter the base name and delete the file extension before pressing return.

Prerequisites

Building and testing Formal requires the Fortran Package Manager (fpm), which can be obtained via a package manager (e.g., brew install fpm on macOS) or by compiling the single-file concatenation of the fpm source that is included among the release assets. For the fpm 0.12.0 release, for example, compiling fpm-0.12.0.F90 and placing the resulting executable file in your PATH suffices.

Building and testing

Vendor	Compiler	Version(s)	Build/Test Command
GCC	gfortran	14-15	fpm test --compiler gfortran --profile release
GCC	gfortran	13	fpm test --compiler gfortran --profile release --flag "-ffree-line-length-none"
Intel	ifx	2025.1.2	FOR_COARRAY_NUM_IMAGES=1 fpm test --compiler ifx --flag "-fpp -O3 -coarray" --profile release
LLVM	flang-new	20-21	fpm test --compiler flang-new --flag "-O3"
LLVM	flang-new	19	fpm test --compiler flang-new --flag "-O3 -mmlir -allow-assumed-rank"
NAG	nagfor	7.2	fpm test --compiler nagfor --flag "-O3 -fpp"

Known Issues

1. With fpm versions after 0.12.0, flang-new can be shortened to flang.
2. With NAG 7.2, Build 7235 or later is recommended, but earlier builds might work.

Documentation

The doc/uml/class-diagram.md file contains a Mermaid script that generates a Unified Modeling Language (UML) class diagram depicting many Formal derived types and their interrelationships. GitHub's web servers render the diagram graphically when viewed in a web browser.