law filter_reverse_sym

bend-mathlib@0.8.1.0 · list.bend:3045

import Base

3045# Filtering commutes with reversing: filter p (reverse xs) = reverse (filter p xs), reversed to rewrite toward the simple side.
3046law filter_reverse_sym:
3047  for ~A: Data
3048  for ~f: A -> Bool
3049  for xs: List<&2, A>
3050  {List.reverse(&2, A, List.filter(~A, ~f, xs)) == List.filter(~A, ~f, List.reverse(&2, A, xs)) : List<&2, A>}