web-sw-cor24-ocaml

Browser-based live demo for the sw-cor24-ocaml integer-subset OCaml interpreter.

Live demo: https://sw-embed.github.io/web-sw-cor24-ocaml/

Part of the Software Wrighter COR24 Tools Project.

Intro

The interpreter is written in Pascal, compiled to p-code, and runs on the canonical COR24 p-code VM (pvm.s); this project assembles pvm.s with the COR24 emulator at build time and runs it inside the browser via WebAssembly. No backend.

Same architecture as the rest of the web-sw-cor24-* family (pascal, snobol4, forth, ...): one Yew SPA, one Trunk build, one cor24-emulator running real COR24 native code under Rust.

Quickstart

# 1. Refresh vendored sources (asm/pvm.s + assets/ocaml.p24m) from
#    sibling repos. Required first time, then any time the upstream
#    interpreter or VM changes.
./scripts/vendor-artifacts.sh

# 2. Run the dev server (port 9735, exclusive dist/ lock).
./scripts/serve.sh

# 3. Open http://localhost:9735/

Pick a demo from the dropdown and hit Run (or Cmd/Ctrl-Enter). Esc stops a running session. Reset reloads the demo source. Clear wipes the output panel.

Demos

23 OCaml programs ship with the build (22 mirrored from ../sw-cor24-ocaml/tests/ via scripts/sync-demos.sh, 1 hand-written):

Demo	Description
factorial	Recursive factorial via let rec; computes 5!.
function-form-let	Sugared let f x y = body form (curried function definitions).
function-keyword	function keyword: shorthand for fun x -> match x with ....
function-pattern-args	Destructuring patterns directly in function arguments.
functions	First-class functions and let bindings.
hello	Smallest possible program: print the integer 42.
higher-order-lists	List.map, List.filter, List.fold_left, List.iter with inline lambdas.
led-blink	Drive the COR24 LED via led_on / led_off. Browser stubs the LED.
led-toggle	Read the COR24 switch and reflect it on the LED.
let-destructure	Destructuring let (a, b) = ..., let h :: t = ..., and friends.
list-module	List.length, List.rev, qualified-name lookups.
lists	List literals, cons, head/tail, is_empty.
lists-pairs-demo	Sum, length, map, swap, countdown -- lists + pairs in one program.
multi-arg	Multi-argument curried function via fun x y -> ....
named-adts	Sum types via type T = C1 | C2 | ... and match expressions.
options	The built-in option type: None and Some x.
pairs	Tuple construction with fst / snd accessors.
patterns	Pattern matching across lists, tuples, options, and literals.
print	print_int and putc writing through the UART.
repl-session	Multi-expression REPL session -- type more lines after the seed runs.
sequencing	Semicolon-sequenced expressions evaluated left-to-right.
strings	String literals, ^ concatenation, print_endline, String.length.
when-guards	match ... when <guard> clauses for conditional pattern arms.

See docs/demos.md for annotated source and expected output for each.

To add a new demo: drop the .ml file in ../sw-cor24-ocaml/tests/, add a mapping line to scripts/sync-demos.sh, append an entry to src/demos.rs, and rerun the sync script.

Architecture

• asm/pvm.s -- vendored copy of the canonical p-code VM from ../sw-cor24-pcode/vm/pvm.s.
• build.rs -- assembles pvm.s via cor24_emulator::Assembler, captures the code_ptr label address, and bakes assets/ocaml.p24m into OUT_DIR.
• src/runner.rs -- 270-line Session over EmulatorCore. Loads pvm.bin at address 0, places the OCaml interpreter image at 0x010000, patches code_ptr so pvm's init_p24m path picks it up on boot, and ticks via emu.run_batch(). Source bytes flow into the UART RX queue terminated by EOT (0x04).
• src/lib.rs -- Yew App: demo dropdown, source editor, output pane, status bar with a budget escalator, REPL input row, octocat corner, footer with build stamp.
• src/demos.rs -- static catalog (include_str! from examples/).
• examples/ -- demo .ml sources synced from the CLI repo.
• scripts/serve.sh -- dev server on port 9735 with an exclusive dist/ lock.
• scripts/build-pages.sh -- release build into pages/ for GitHub Pages, same lock.

Build for GitHub Pages

./scripts/build-pages.sh
git add pages/
git commit -m "Release: deploy <date>"
git push

The --public-url is /web-sw-cor24-ocaml/ so paths resolve under https://sw-embed.github.io/web-sw-cor24-ocaml/.

Tests

cargo test --lib

4 unit tests:

• runner::tests::print_int_42_runs_to_completion_with_42_in_output -- end-to-end: source bytes -> UART -> pvm boot -> OCaml interp -> 42 in cleaned output. Confirms the whole stack including multi-unit XCall / IRT through the real pvm.s.
• demos::tests::default_is_hello, demos::tests::names_are_unique, demos::tests::only_repl_session_is_interactive -- catalog invariants.

Related projects

• sw-cor24-ocaml -- the OCaml interpreter (Pascal -> p-code) that this demo runs.
• sw-cor24-pcode -- canonical p-code VM (pvm.s), assembler (pa24r), linker (p24-load), tracer (pv24t).
• sw-cor24-emulator -- COR24 native CPU emulator. Hosts pvm.s here.
• web-sw-cor24-pascal, web-sw-cor24-snobol4, web-sw-cor24-basic -- sibling browser demos in the same family.

Links

• Blog: Software Wrighter Lab
• Discord: Join the community
• YouTube: Software Wrighter

Copyright

Copyright (c) 2026 Michael A. Wright

License

MIT. (C) 2026 Michael A Wright. See LICENSE.