law find_append_sym

bend-mathlib@0.8.1.0 · list.bend:3099

import Base

3099# Finding in an append finds in the first part, or else in the second, reversed to rewrite toward the simple side.
3100law find_append_sym:
3101  for ~A: Data
3102  for ~f: A -> Bool
3103  for xs: List<&2, A>
3104  for ys: List<&2, A>
3105  {Maybe.or(&2, A, List.find(~A, ~f, xs), List.find(~A, ~f, ys)) == List.find(~A, ~f, List.append(&2, A, xs, ys)) : Maybe<&2, A>}