law maybe_is_none_map_sym

bend-mathlib@0.8.1.0 · maybe.bend:323

import Base

323# Mapping keeps whether a value is absent, reversed to rewrite toward the simple side.
324law maybe_is_none_map_sym:
325  for ~A: Data
326  for ~B: Data
327  for ~f: A -> B
328  for m: Maybe<&2, A>
329  {Maybe.is_none(&2, A, m) == Maybe.is_none(&2, B, Maybe.map(&2, A, B, f, m)) : Bool}