Lean4 Ffi Constructor Layout

Quality score: 70/100 · Category: General · Sub-category: general-misc

Lean 4 FFI memory layout for constructors with mixed object and scalar fields. Use when: (1) assertion violation "i < lean_ctor_num_objs(o)" accessing constructor fields, (2) assertion violation "offset >= lean_ctor_num_objs(o) * sizeof(void*)" with scalar getters, (3) lean_ctor_get_uint8/uint16/uint32 crashes or returns garbage, (4) creating FFI bindings for Lean inductives or structures with small integer fields (UInt8, UInt16, UInt32). Covers lean_alloc_ctor, lean_ctor_get, lean_ctor_set, and scalar field offset calculation.

What this skill does

Lean4 Ffi Constructor Layout is a production-ready Claude Code skill (quality score 70/100) in the general-misc sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/lean4-ffi-constructor-layout/ and loads when your prompt matches the skill's trigger.

When to invoke it: Use when: (1) assertion violation "i < lean_ctor_num_objs(o)" accessing constructor fields, (2) assertion violation "offset >= lean_ctor_num_objs(o) * sizeof(void*)" with scalar getters, (3) lean_ctor_get_uint8/uint16/uint32 crashes or returns garbage, (4) creating FFI bindings for Lean inductives or structures with small integer fields (UInt8, UInt16, UInt32). Covers lean_alloc_ctor, lean_ctor_get, lean_ctor_set, and scalar field offset calculation.

Who uses this skill

The Lean4 Ffi Constructor Layout skill is built for Claude Code users and developers across all disciplines looking for general-purpose AI assistance. It is part of the open ClaudSkills registry, a community-curated catalog of 15,000+ capabilities you can install for Claude Code — the Claude CLI agent.

How to install

Free

Manual install (2 steps)

mkdir -p ~/.claude/skills/lean4-ffi-constructor-layout
curl -L https://claudskills.com/skills/lean4-ffi-constructor-layout/SKILL.md \
  -o ~/.claude/skills/lean4-ffi-constructor-layout/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/lean4-ffi-constructor-layout/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/lean4-ffi-constructor-layout/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\lean4-ffi-constructor-layout\SKILL.md on Windows. See the full install guide for step-by-step instructions.

Pro

One-click install via the desktop app

The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.

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