Nat.add_sub_add_left_sym: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/nat.bend as Nat
Lines 4521-4526 of bend-mathlib@0.8.1.0/nat.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/nat.bend&start_line=4521&end_line=4526

import Base

# A common left summand cancels in a difference: (k + n) - (k + m) = n - m, reversed to rewrite toward the simple side.
law add_sub_add_left_sym:
  for k: Nat
  for -n: Nat
  for -m: Nat
  {Nat.sub(n, m) == Nat.sub(Nat.add(k, n), Nat.add(k, m)) : Nat}

Uses (5):
  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=Base/base.bend&name=Nat.sub
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/nat.bend&name=add_sub_add_left