ott (next‑gen)

Rust + WASM + Typst reimplementation of the Ott toolchain.

What you can do today

• Parse a large subset of Ott’s .ott DSL (tested against upstream Ott tests/*.ott, except known negative tests).
• Run basic semantic checks (duplicate grammar roots, subrules references, duplicate rule names).
• Render grammars and inference rules in Typst via a WASM plugin.
• Parse and validate object-language terms/snippets in Typst from a loaded Ott spec (ott-file → #ott[...]).

Repository layout

• crates/ott-core/ — parser + basic checks
• crates/ott-render/ — Typst render IR + CBOR serialization
• crates/ott-cli/ — CLI (check, render-json, render-cbor)
• crates/ott-wasm/ — WASM plugin (parse_rules)
• typst/ott.typ — Typst-side renderer (uses @preview/curryst)
• demo.typ — root demo document

Build & run the Typst demo

Prerequisites:

• Rust toolchain with wasm32-unknown-unknown target
• Typst >= 0.14 (uses built-in cbor(...))

Build the WASM plugin and copy it into the Typst package directory:

cargo build -p ott-wasm --release --target wasm32-unknown-unknown
cp target/wasm32-unknown-unknown/release/ott_wasm.wasm typst/plugins/ott.wasm

Compile the demo:

typst compile --root . demo.typ demo.pdf

Use in your own Typst document

#import "typst/ott.typ": render, ott-file

// Render grammar + inference rules from a spec
#render(read("path/to/spec.ott"))

// Build a term parser.
// - If `root` is omitted, it behaves like Ott's `user_syntax` (tries all roots/metavars).
// - Specify `root` only to disambiguate.
#let ott = ott-file(read("path/to/spec.ott"))
// #let ott = ott-file(read("path/to/spec.ott"), root: "t")

// Parse + typeset terms
#ott[x]
#ott[`\x.x`]
$ #ott[`[x|->x]x`] $

Notes:

• Term parsing uses {{ typst ... }} hom templates in your .ott spec to pretty-print object-language snippets into Typst math.
  • If a production/metavar has no typst hom, we fall back to rendering the original source slice as math text.
  • In typst homs, use Typst math symbols (e.g. tack.r, mapsto, lambda, arrow.r) instead of LaTeX commands (\\vdash, \\mapsto, ...).
• Filter-mode ([[...]]) is not implemented; use ott-file(...) + the returned ott[...] function instead.
• Proof-assistant backends are not implemented yet.

Design / plan

See: docs/plans/2026-03-04-ott-typst-rust-nextgen-design.md.