law length_filter_le

bend-mathlib@0.8.1.0 · list.bend:688

import Base

688# Filtering never makes a list longer.
689law length_filter_le:
690  for ~A: Data
691  for ~f: A -> Bool
692  for xs: List<&2, A>
693  {Nat.is_le(List.length(&2, A, List.filter(~A, ~f, xs)), List.length(&2, A, xs)) == True{} : Bool}