Stream: contributing

Topic: List.prepend_if_ok, map3, map4 (#9596)

Dzmitry Misiuk (Jul 23 2026 at 21:49):

Lining up a few more from #9596, all just rounding out existing List families:

• prepend_if_ok — the prepend counterpart to the existing append_if_ok
• map3 / map4 — following on from map2

All pure Roc over existing primitives, no new low-level ops. Thinking prepend_if_ok as one small PR and map3 / map4 as a pair — anything here you'd rather see as Iter, or hold off on?

Dzmitry Misiuk (Jul 24 2026 at 11:21):

Both up:

• prepend_if_ok → #10355 (mirrors append_if_ok)
• map3 / map4 → #10356 (mirror map2's existing loop)

Pure Roc, no new low-level ops — each with a doc-test + repl snapshot.

Last updated: Aug 12 2026 at 12:35 UTC