Algebra.nat_add_four: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/algebra.bend as Algebra
Lines 141-147 of bend-mathlib@0.8.1.0/algebra.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/algebra.bend&start_line=141&end_line=147

import Base
import bend-mathlib@0.8.1.0/nat.bend as MNat

# Nat addition's middle-four interchange (the same statement as MNat.add_add_add_comm).
law nat_add_four:
  for +a: Nat
  for +b: Nat
  for +c: Nat
  for +d: Nat
  {Nat.add(Nat.add(a, b), Nat.add(c, d)) == Nat.add(Nat.add(a, c), Nat.add(b, d)) : Nat}

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.add
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/algebra.bend&name=internal_nat_add_assoc
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/algebra.bend&name=internal_nat_add_comm
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/algebra.bend&name=op_four