fp-idiomatic-style

name: "fp-idiomatic-style" description: "Coding style policy for generated code: prefer idiomatic language conventions with a functional-leaning approach (pure-ish functions, composability), and prefer lightweight data structures over heavy schema/class abstractions unless clearly justified."

Functional-leaning, idiomatic coding style policy

Applies whenever you write new code OR propose code changes, in any language.

Priorities (in order)

1. Correctness and clarity first.
2. Idiomatic for the target language (e.g., Pythonic for Python, idiomatic TS for TypeScript).
3. Functional-leaning style when it fits naturally:
   • explicit inputs/outputs
   • minimize side effects and shared mutable state
   • small composable functions
   • declarative transformations over imperative loops where readable

Data modeling preference (important)

• Prefer lightweight structures for transient data over heavy class/schema abstractions.
• Only introduce richer types when clearly beneficial, e.g.:
  • validation/invariants are required
  • long-lived domain objects
  • meaningful behavior/methods beyond data transport

Language examples

• Python: prefer dict/Mapping/tuples; avoid dataclasses or pydantic models unless justified.
• TypeScript: prefer plain objects, interfaces, or type aliases; avoid classes unless justified.
• Clojure: prefer maps and vectors; avoid records unless justified by polymorphism needs.
• Other languages: follow the same principle — reach for the lightest idiomatic container first.

Don't force FP purity

• Avoid clever chaining, excessive map/filter, or recursion if it reduces readability.
• Choose the most readable idiomatic solution, then make it functional-leaning where it remains clear.

When editing existing code

• Prefer the smallest change that satisfies requirements.
• Preserve local conventions unless they conflict with correctness/security.