BASIC in Roc: where it stands

roc-apps master, at 5a6f199. Parked. The summary is the essay.

The suites

• NBS: 195 pass, 0 fail, 13 unjudged of 208. An unjudged program prints no verdict of its own.
• Games: 55 of 99 match basic101's captured output byte for byte. The games come from basic101's own tests, listings and captures together.
• The fast path agrees with the full evaluator on every program (basic/check-fast.sh).

What runs, precisely

program	built by, from	mode	target	used for
the Roc compiler	roc-lang's nightly binary, nightly-2026-09-11-793f9d8	as published; we do not build it	x86-64	every build below
basic-run	the Roc compiler, from BasicRun.roc (Machine.roc)	--opt=dev	x86-64	NBS and games, one process a program
basic-check	the Roc compiler, from BasicCheck.roc (Machine.roc)	--opt=dev	x86-64	the fast-path check
basic.wasm, the page	the Roc compiler, from BasicApp.roc (Machine.roc)	--opt=dev	wasm32	the browser, preview :9203

All three are the same interpreter. The old one (Basic.roc, Pages.roc) is deleted. No LLVM until the next major checkpoint.

The machine

What never changes during a run is Parse.Program. What a statement changes is Machine.M. The devices (terminal, screen, memory, framebuffer) are Devices.D, behind one reference. INPUT allocates 5 times a statement; the ladder holds it there.

When we return

1. Better coverage on the games. life, poetry, splat and superstartrek are among the 44 that still differ: interpreter work, one game at a time.
2. The ECMA-55 load checks, 150 to 370 ms a program, the largest cost left in NBS.

Numbers: basic-timings.