law foldl_reverse_sym

bend-mathlib@0.8.1.0 · list.bend:3065

import Base

3065# A left fold over the reverse is a right fold with the arguments flipped, reversed to rewrite toward the simple side.
3066law foldl_reverse_sym:
3067  for ~a: Quant
3068  for ~A: Kind(a)
3069  for ~B: Type
3070  for ~f: B -> A -> B
3071  for xs: List<a, A>
3072  for -z: B
3073  {List.foldr(~a, ~A, ~B, ~(x => y => f(y, x)), xs, z) == List.foldl(~a, ~A, ~B, ~f, List.reverse(a, A, xs), z) : B}