law drop_left_sym

bend-mathlib@0.8.1.0 · list.bend:2562

import Base

2562# Dropping the length of the first part of an append gives the second part, reversed to rewrite toward the simple side.
2563law drop_left_sym:
2564  for -a: Quant
2565  for -A: Kind(a)
2566  for xs: List<a, A>
2567  for ys: List<a, A>
2568  {ys == List.drop(a, A, List.append(a, A, xs, ys), List.length(a, A, xs)) : List<a, A>}