law take_append_sym

bend-mathlib@0.8.1.0 · list.bend:2573

import Base

2573# Taking past the first part of an append keeps it and takes the rest from the second part, reversed to rewrite toward the simple side.
2574law take_append_sym:
2575  for -a: Quant
2576  for -A: Kind(a)
2577  for xs: List<a, A>
2578  for -ys: List<a, A>
2579  for -n: Nat
2580  {List.append(a, A, xs, List.take(a, A, ys, n)) == List.take(a, A, List.append(a, A, xs, ys), Nat.add(List.length(a, A, xs), n)) : List<a, A>}