law lookup_exact

bendtorch-core@0.1.0.0 · src/autograd/backward_LAWS.bend:317

import Base
import bendtorch-core@0.1.0.0/src/autograd/backward.bend as Backward

317# Ids (C2): id k reads exactly the element with k older elements, and an id
318# the list does not hold reads None, never another element.
319law lookup_exact:
320  for -A: Data
321  for +newer: List<&2, A>
322  for +item: A
323  for +rest: List<&2, A>
324  {Backward.lookup(A, List.append(&2, A, newer, item <> rest), List.length(&2, A, rest)) == Some{item} : Maybe<&2, A>}