List.drop_left: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/list.bend as List
Lines 1093-1099 of bend-mathlib@0.8.1.0/list.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/list.bend&start_line=1093&end_line=1099

import Base

# Dropping the length of the first part of an append gives the second part.
law drop_left:
  for -a: Quant
  for -A: Kind(a)
  for xs: List<a, A>
  for ys: List<a, A>
  {List.drop(a, A, List.append(a, A, xs, ys), List.length(a, A, xs)) == ys : List<a, A>}

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.append
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.drop
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.length
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/list.bend&name=drop_zero