fortran

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description: Modern Fortran rules for scientific computing, modules, explicit interfaces, kind parameters, memory safety, and testing globs: ["/*.f", "/.f90", "**/.f95", "/*.f03", "/.f08", "**/.for", "**/.ftn", "CMakeLists.txt", ".cmake", "Makefile"] alwaysApply: false

Fortran Programming Guidelines

Basic Principles

• Use modern Fortran standards such as Fortran 2003, 2008, or newer.
• Use implicit none in every program unit.
• Put procedures in modules to provide explicit interfaces.
• Keep modules focused and place each major module in its own file.
• Prefer clear, structured code over clever language tricks.
• Avoid obsolete features such as COMMON blocks, GOTO-heavy control flow, and numeric labels.

Kinds and Types

• Define numeric kind parameters in one shared module, such as kind_mod.
• Use real(kind=dp) or the project-approved real kind for floating point values.
• Use integer(kind=i4) or the project-approved integer kind for integer values.
• Define constants such as pi explicitly.
• Include units in comments for physical quantities.
• Use derived types to group related data instead of passing many primitive arguments.

Naming and Style

• Use lowercase for language keywords and most identifiers.
• Use underscores for multi-word names.
• Avoid names that differ only by case.
• Use descriptive names for procedures and state.
• Repeat the procedure or module name after end statements.
• Keep indentation consistent in do, if, select case, and module blocks.

Procedures

• Keep subroutines and functions short and single-purpose.
• Use intent(in), intent(out), or intent(inout) for every dummy argument.
• Keep functions free of side effects whenever possible.
• Prefer early validation and clear returns over deep nesting.
• Use use, only: when importing from modules.

Memory and Arrays