Menu

Search

Assembling in Tyu

Theme: Symblix Light

The Browser REPL

Write, check, and run Tyu in your browser — no install. The book's labs, preloaded.

Audience: anyone who wants to try Tyu right now. Purpose: use the browser REPL and find each book lab in it. Prerequisites: a browser tab. Nothing else — no toolchain, no account, no network after the page loads.

Open the REPL — or reach it any time from the site header.

# What it is

The REPL is the language running in your tab, shipped with this site and served from /repl/. It is fully static and self-contained: every artifact it loads is same-origin and SHA-256-pinned, and the page refuses to boot a mismatched artifact. No servers, no post-boot network.

  • Editor — CodeMirror 6 with a first-party Tyu grammar (syntax highlighting, bracket matching). Falls back to a plain textarea if the editor bundle fails its integrity check; the page never blanks.
  • Two execution backends — the interpreter (default) and the wasm32 backend (the compiler’s own WebAssembly code generator). The active substrate is always visible in the header.
  • The checker, not a suggestion box — same diagnostics as langc: red labs are rejected with their exact error codes.
  • A debug console — call frames, post-mortem backtrace with click-to-source, an --emit=ir pane, and a per-submission transcript.
  • The book’s labs as one-click examples — 53 runnable and 24 native-only, classified from the labs’ own expected verdicts; a red lab teaches “the checker explains itself”, a green lab teaches “the checker accepts”.

Run submits the whole buffer (Ctrl+Enter); submit feeds the live session (Ctrl+Shift+Enter); step resumes a fuel-suspended phrase (Ctrl+.).

# The labs, chapter by chapter

Deep links open the REPL with the lab loaded: /repl/#example=chNN/<lab-name>. The lab names match docs/book/labs/ (and the mirror under /book/labs/ on this site).

Green labs compile clean in the browser session; red labs are rejected with the documented error code. Labs marked native-only cannot run in the browser — module submissions compile (imports are signature-only), so a lab’s main cannot be invoked and run-time traps need the native toolchain; the REPL says why for each such lab.

Chapter Try in the REPL
1 — The Rigor Is the Engine green-01-hello , green-02-promise-kept , red-01-main-no-exit
2 — First Words green-01-arithmetic-check , green-03-while-counter , red-01-underflow
3 — Types green-01-enums , red-02-bitcast-width
4 — Contracts green-02-ensures , red-01-flat-sandwich
5 — Effects and Capabilities green-01-alloc-effect , red-01-undeclared-effect
6 — The Stack Has a Shape green-01-stack-shapes , red-02-while-grows
7 — Places, Borrowing, Ownership labs ch07 — open in the REPL’s example list
8 — Touching Hardware: MMIO labs ch08 — native-only (MMIO)
9 — Factoring labs ch09
10 — Decomposition labs ch10 — includes module labs
11 — Shared State and Interrupts labs ch11 — native-only (ISRs)
12 — Tasks and Channels labs ch12
13 — Field Updates on Untrusted Media labs ch13
14 — Proving the Program labs ch14 — the proof pipeline runs natively

The REPL’s own example list (in the page) is the complete, classified corpus; this table is just the front door.

# Running it locally

The REPL is built from the repository, and this site vendors the built artifacts:

# from a tyu checkout — build the artifact set into web/
bash ci/wasm.sh build-web
cd web && python3 -m http.server 8080   # → http://localhost:8080

This site’s copy lives at /repl/ and is refreshed from the pinned upstream/tyu submodule with scripts/sync-web.sh — see the repository README for the toolchain details (Node ≥ 20, wasm-bindgen-cli 0.2.108, brotli).

On this page