forthling playground

Forth-2012 in your browser: forthling, a small Forth interpreter in Rust, compiled to WebAssembly. It runs on your own computer, in a sandbox.

Tutorial

stack starting…

Forth code

Ctrl+Enter runs

New to Forth? Tutorial has 20 short lessons, ten for beginners and ten beyond, that check your answers. Words you define stay until you start over. Each run may take 10 million steps and print 1 MiB. Files are kept in this browser, also when you start over, up to 4 MiB: INCLUDE name.fs, the FILE words and BLOCK use them, and what a program writes is kept too. Try WORDS, SEE SQUARE, ALSO JSON for the JSON words, or ALSO DEBUG TRACE-ON to see each word run (TRACE-OFF stops it). Step through runs the code, then lets you follow it word by word, forwards and back, with the stack before and after each word; BREAK (after ALSO DEBUG) marks a place to jump to.