law contains_append

bend-mathlib@0.8.1.0 · list.bend:665

import Base

665# An append contains x iff either part does.
666law contains_append:
667  for ~A: Data
668  for ~eq: A -> A -> Bool
669  for xs: List<&2, A>
670  for -ys: List<&2, A>
671  for +x: A
672  {List.contains(~A, ~eq, List.append(&2, A, xs, ys), x) == Bool.or(List.contains(~A, ~eq, xs, x), List.contains(~A, ~eq, ys, x)) : Bool}