ProofTree.hi_fst: law of lawful-arrays@0.1.0.0
Import: import lawful-arrays@0.1.0.0/proof_tree.bend as ProofTree
Lines 78-82 of lawful-arrays@0.1.0.0/proof_tree.bend: https://jend.leeeet.dev/read.txt?path=lawful-arrays@0.1.0.0/proof_tree.bend&start_line=78&end_line=82

import Base

law hi_fst:
  for -T: Type
  for -xs: Array<T>
  for r: Array<T> & T
  {Pair.fst(Array<T>, T, Array.swap.hi(T, xs, r)) == ANode{xs, Pair.fst(Array<T>, T, r)} : Array<T>}

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array.swap.hi
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair.fst
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma