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categories-functors skill

by parcadei·parcadei/Continuous-Claude-v3·3.9k stars·MIT

Problem-solving strategies for categories functors in category theory

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Install the categories-functors skill

A skill is a folder. Copy it into your agent's skills folder and the agent loads it when the task matches its description.

git clone --depth 1 https://github.com/parcadei/Continuous-Claude-v3.git /tmp/Continuous-Claude-v3
mkdir -p ~/.claude/skills
cp -r /tmp/Continuous-Claude-v3/.claude/skills/math/category-theory/categories-functors ~/.claude/skills/categories-functors
available in every project

In the Claude apps, zip the folder and upload it from the Skills settings. The folder on GitHub

The instructions your agent would load

SKILL.md as published, without the frontmatter. Read it on GitHub

Categories Functors

When to Use

Use this skill when working on categories-functors problems in category theory.

Decision Tree

  1. Verify Category Axioms
  • Objects and morphisms (arrows) defined?
  • Identity morphism for each object: id_A: A -> A
  • Composition associative: (f . g) . h = f . (g . h)
  • Write Lean 4: theorem assoc : (f ≫ g) ≫ h = f ≫ (g ≫ h) := Category.assoc
  1. Check Functor Properties
  • F: C -> D maps objects to objects, arrows to arrows
  • Preserves identity: F(idA) = id{F(A)}
  • Preserves composition: F(g . f) = F(g) . F(f)
  • Write Lean 4: theorem comp : F.map (g ≫ f) = F.map g ≫ F.map f := F.map_comp
  1. Functor Types
  • Covariant: preserves arrow direction
  • Contravariant: reverses arrow direction
  • Faithful/Full: injective/surjective on Hom-sets
  • Equivalence: full, faithful, essentially surjective
  1. Common Functors
  • Forgetful functor: forgets structure (e.g., Grp -> Set)
  • Free functor: left adjoint to forgetful
  • Hom functor: Hom(A, -) or Hom(-, B)
  • Power set functor: Set -> Set via X |-> P(X)
  1. Verify with Lean 4
  • Compiler-in-the-loop: write proof, lake build checks
  • Mathlib has full category theory library
  • See: .claude/skills/lean4-functors/SKILL.md for exact syntax

Tool Commands

Lean4_Category

# Lean 4 with Mathlib: import CategoryTheory.Category.Basic

Lean4_Functor

# Lean 4: theorem map_comp (F : C ⥤ D) : F.map (g ≫ f) = F.map g ≫ F.map f := F.map_comp

Lean4_Build

lake build  # Compiler-in-the-loop verification

Cognitive Tools Reference

See .claude/skills/math-mode/SKILL.md for full tool documentation.

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