LL Playground

Write an LLP program, compile it, and run it — entirely in your browser.

Type or paste an LL program (the same forbidden / advance notation used throughout the book) into the box below and press Compile & run. The page compiles it to JavaScript using the same compiler (llc.py) the book's own demos are built with — running locally in your browser via Pyodide, so nothing you type ever leaves your machine — and mounts it on the same step / run / reset widget used elsewhere on this site.

This playground supports LLP programs written with an explicit forbidden (j) : … => advance : … rule (array, linked-list, or in-place form), plus plain guard-free (imperative) LL programs, which step through their assignments and loop iterations instead. See What are LLP Algorithms? for the framework, or Chapter 2 for worked examples. Not every program in the book compiles here yet — the browser compiler covers a growing subset of the language; unsupported constructs are reported as a compile error rather than failing silently. A standalone command-line compiler (targeting Java, Python, and C++) is planned as a separate release.