Deque.Deque.pop_back.push_back: law of bend-kit-collections@0.1.4.1
Import: import bend-kit-collections@0.1.4.1/deque.bend as Deque
Lines 197-203 of bend-kit-collections@0.1.4.1/deque.bend: https://jend.leeeet.dev/read.txt?path=bend-kit-collections@0.1.4.1/deque.bend&start_line=197&end_line=203

import Base

# LAW: pop_back undoes push_back
law Deque.pop_back.push_back:
  for -A: Data
  for -x: A
  for  d: Deque<&2, A>
  {Deque.pop_back(&2, A, Deque.push_back(&2, A, x, d))
   == Some{(x, d)} : Maybe<&1, A & Deque<&2, A>>}

Uses (6):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=bend-kit-collections@0.1.4.1/deque.bend&name=Deque
  https://jend.leeeet.dev/definition.txt?path=bend-kit-collections@0.1.4.1/deque.bend&name=Deque.pop_back
  https://jend.leeeet.dev/definition.txt?path=bend-kit-collections@0.1.4.1/deque.bend&name=Deque.push_back