Algebra.nat_mul_four_sym: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/algebra.bend as Algebra
Lines 415-421 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=415&end_line=421

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

# Nat multiplication's middle-four interchange (the same statement as MNat.mul_mul_mul_comm), reversed to rewrite toward the simple side.
law nat_mul_four_sym:
  for +a: Nat
  for +b: Nat
  for +c: Nat
  for +d: Nat
  {Nat.mul(Nat.mul(a, c), Nat.mul(b, d)) == Nat.mul(Nat.mul(a, b), Nat.mul(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.mul
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/algebra.bend&name=nat_mul_four