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Mojo Cheat Sheets

Documents
mojo-cheat-sheets

Mojo Cheat Sheets is an Agent Skill for documents published in the modular/modular repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Build and update a Mojo language cheat sheet in this folder. Use when editing a card's content, adding a card, or rebuilding its PDF/PNG/SVG outputs.

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QUICK START

How to use this skill

Bring this guide into your coding agent with a prompt tailored to the tool you use.

  1. Open your project in Codex.
  2. Copy and paste the prompt below.
  3. Review files and risks before approving any action.
Prompt to paste
Inspect the Agent Skill at https://github.com/modular/modular/blob/HEAD/mojo/docs/cheatsheet-tooling/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/mojo-cheat-sheets, but wait for my approval before writing files or running scripts.

Copying this prompt does not install or run the skill. Review third-party files before use.

Update a Mojo cheat sheet

One-page reference cards for the Mojo language, rendered from HTML sources to PDF, PNG, and SVG (light + dark). Use this skill to update an existing card or add a new one.

Where things are

  • src/body-<topic>.html — the content of one card; this is what you edit.
  • src/_head.html, src/_foot.html — shared CSS, palette, header.
  • bin/build.py — assembles a card and renders all formats. It discovers cards from the body files present; there is no card list to edit.
  • dist/ — produced files. Generated; never edit by hand.

Workflow

  1. Anchor to the reference. Every behavioral claim on a card must match the Mojo reference docs under mojo/docs/reference/, or a short program you compile to confirm it. Do not rely on memory or older syntax.

  2. One card at a time.

  3. Edit the source, never the output. Change src/body-<topic>.html.

  4. A card's title, subtitle, and optional layout live in comment lines at the top of its body file:

    <!-- title: ... -->
<!-- subtitle: ... -->
<!-- layout: portrait | landscape -->   # optional; default portrait

    portrait is 2 columns / ~900px; landscape is 3 columns / ~1100px. Fine-tune with <!-- columns: N --> and <!-- width: W -->.

  5. Rebuild and look: python3 bin/build.py <topic>, then open dist/mojo-cheat-sheet-<topic>-light.png.

  6. Compiler-check new claims with a tiny snippet before asserting them.

  7. Discuss restructuring a card or adding a new one before doing it.

Conventions

  • Each card stands alone. No cross-references between cards.
  • One space before a trailing # comment; keep all trailing comments.
  • No em-dashes in prose.
  • Keep code lines short enough not to wrap.
  • Current Mojo syntax only: def (no fn), comptime (not alias), read/mut/out/var/ref conventions, t"..." template strings.
  • The legend on each card is a fixed full palette, identical across all cards; it is generated by the build, not maintained by hand.

Build everything

python3 bin/build.py all rebuilds every card present and the combined PDFs. The build shrinks SVGs with svgo so they stay under the repo's 2 MB file cap.

Required tools

See README.md.