def step
import ezx@1.11.0.0/src/sha/nar.bend as Narimport Base
413# one step of the build
414def step(st: State) -> Move:
415 State{es, +top, up} = st
416 match es:
417 case []:
418 close(top, up, [])
419 case +e <> t:
420 step.ent(String.eq(ent.at(e), under(frame.at(top), ent.name(e))), e, t, top, up)