Category Theory Wiki

An Obsidian vault (wiki/) built from Seven Sketches in Compositionality, Category Theory for Scientists (arXiv:1302.6946, PDF in Books/), The Dao of Functional Programming and Kittenlab.jl: one note per concept, exercises with solutions, and Julia (Catlab), Lean (Mathlib) and Haskell code for each idea. Start with wiki/Start Here.md.

Running the code tabs

• Julia: the snippets target Catlab v0.16 (] add Catlab@0.16). Each Julia tab starts with a Docs: line linking the Catlab v0.16 / GATlab / ACSets documentation (or the Kittenlab lecture) for what it uses; a Builds on: line names notes whose Julia code must be run first (the Kittenlab-style mini-library of Category, Preorder, VCategory, …). Kittenlab itself: ] add https://github.com/AlgebraicJulia/Kittenlab.jl. See wiki/Catlab.md.
• Haskell: plain GHC; most snippets run with runghc after adding a main.
• Lean 4: Mathlib declaration names (#checks); they follow current Mathlib naming and may drift as Mathlib evolves.

The vault is also published as a static site with Quartz from the site/ directory:

cd site
npm ci
npx quartz build -d ../wiki --serve   # preview at http://localhost:8080

Pushing to master runs .github/workflows/deploy.yml, which builds the site and deploys it to GitHub Pages (repository Settings → Pages → Source: GitHub Actions).

Site-specific pieces:

• site/quartz/plugins/transformers/tikz.ts renders the vault's ```tikz blocks to SVG at build time with node-tikzjax; results are cached in site/.tikz-cache/ (committed, so CI only renders new diagrams).
• site/quartz/plugins/transformers/tabs.ts renders the tabs ```` blocks of the Obsidian Markdown Tabs plugin as tabbed code panels; text outside the code fences in a tab (the Docs: lines) is rendered as Markdown.
• site/quartz/plugins/transformers/ofm.ts (patched): a wikilink whose alias contains math or code, e.g. [[Corelation|$\mathbf{Corel}$]], is turned into a Markdown link so the alias is rendered by KaTeX instead of breaking the link. Inside tables, write the alias separator as \| ([[Note\|alias]]), which both Obsidian and Quartz understand.
• Math is rendered with KaTeX ($…$, $$…$$); diagrams are tikz blocks (tikz-cd, rendered at build time) — Mermaid blocks are supported by Quartz as well. Typst is not rendered by Quartz, so the vault uses LaTeX throughout.
• wiki/index.md is the site's landing page; it transcludes Start Here.