Algebra.nat_add_four_sym: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/algebra.bend as Algebra
Lines 384-390 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=384&end_line=390

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), reversed to rewrite toward the simple side.
law nat_add_four_sym:
  for +a: Nat
  for +b: Nat
  for +c: Nat
  for +d: Nat
  {Nat.add(Nat.add(a, c), Nat.add(b, d)) == Nat.add(Nat.add(a, b), Nat.add(c, d)) : Nat}

Uses (4):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.sym
  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=nat_add_four