simple-modern-fortran

name	simple-modern-fortran
description	Use when editing SIMPLE's Fortran code and you need repo-specific guidance on the modern Fortran style used here, including modules, submodules, type-bound procedures, abstract command interfaces, generated sources, OpenMP-aware code, and common patterns for extending the code safely.

Modern Fortran In SIMPLE

SIMPLE already uses modern Fortran heavily. Follow the local style instead of introducing foreign patterns.

Patterns To Expect

• Module-based APIs with use ..., only: ...
• Abstract base types with deferred procedures, e.g. command interfaces
• Type-bound procedures and generic bindings on domain objects
• Submodules for large types such as image, oris, sp_project, and polarft_calc
• Allocatable state and explicit lifecycle methods such as new, copy, kill
• OpenMP-aware loops and shared-memory execution paths
• C interoperability for FFTW and selected low-level helpers

Best Entry Files

• src/main/simple_builder.f90
• src/main/simple_cmdline.f90
• src/main/image/simple_image.f90
• src/main/project/simple_sp_project.f90
• src/main/commanders/simple/simple_commander_base.f90

Local Conventions

• Prefer adding behavior through existing types and submodules rather than creating detached helper files.
• Keep orchestration in commanders/strategies and numerical work in domain modules.
• Reuse parameters, cmdline, and builder instead of inventing parallel configuration plumbing.
• In commanders, normalize and validate cmdline before the single params%new(cline) call; never construct a parameters object twice in one commander execution path.
• After params%new(cline) or a builder parameter initializer, treat the typed parameters object as authoritative. Use params%... fields in workflow logic instead of re-reading parsed values with cmdline%get_iarg, get_rarg, or get_carg.
• New SIMPLE command-line arguments must be represented in src/main/params/simple_parameters.f90 and registered through the normal parsing/checking path before downstream code consumes them.
• For project-file workflows, do not pass native box/smpd through child command lines. Project metadata is the native sampling authority; pass box_crop only when a deliberate crop is requested and let parsing derive smpd_crop.
• Keep child command lines sparse. Set only values that change behavior or preserve execution mode rather than restating defaults already supplied by the child commander or parameters.
• Preserve new/kill lifecycle symmetry for stateful types.
• Watch for generated sources from scripts/simple_args_generator.pl and git-hash insertion during builds.

Debugging And Build Notes

• Debug build: cmake .. -DCMAKE_BUILD_TYPE=Debug
• Helpful notes: doc/how2s/how2debug_fortran.txt
• Many objects expose derived-type state through type-bound methods; prefer following those paths before adding temporary print code.

When Extending Code

• Match the existing folder ownership before adding files.
• If a large module already uses submodules, extend the submodule structure instead of inflating the parent interface file.
• If a workflow already has ui -> exec -> commander -> strategy, add the feature in the narrowest layer that owns it.
• For parameter parsing changes, read .github/skills/simple-main-params/SKILL.md.