def add_undo

bendvy-ecs-core@0.1.0.4 · transaction.bend:30

import Base

30# Trusted lower-level operation: push an affine inverse onto the journal.
31# Caller must ensure it restores the matching change and preserves other
32# owners. Inverses execute newest first on failure, not on successful commit.
33def add_undo(~W: Type, ~E: Data, tx: Tx<W, E>, inverse: W -> W) -> Tx<W, E>:
34  match tx:
35    case Tx{world, undo, commands, events,trace}:
36      Tx{world, inverse <> undo, commands, events,trace}