def sub_add_r

bend-collections-laws-math@1.0.0.0 · proofs/math/typed/f64round.bend:199

import Base
import bend-collections-laws-math@1.0.0.0/proofs/lib/nat.bend as N
import bend-collections-laws-math@1.0.0.0/proofs/lib/lemmas/proofs/nat_algebra.bend as NA

199def sub_add_r(+a: Nat, +b: Nat, +m: Nat, +h: {Nat.is_le(m, a) == True{} : Bool}) -> {Nat.sub(Nat.add(a, b), m) == Nat.add(Nat.sub(a, m), b) : Nat}:
200  +d = Nat.sub(a, m)
201  Equal.trans(Nat, Nat.sub(Nat.add(a, b), m), Nat.sub(Nat.add(Nat.add(m, d), b), m), Nat.add(d, b), Equal.cong(Nat, Nat, z => Nat.sub(Nat.add(z, b), m), a, Nat.add(m, d), Equal.sym(Nat, Nat.add(m, d), a, N.sub_add(a, m, h))), Equal.trans(Nat, Nat.sub(Nat.add(Nat.add(m, d), b), m), Nat.sub(Nat.add(m, Nat.add(d, b)), m), Nat.add(d, b), Equal.cong(Nat, Nat, z => Nat.sub(z, m), Nat.add(Nat.add(m, d), b), Nat.add(m, Nat.add(d, b)), NA.add_assoc(m, d, b)), N.add_sub_cancel(m, Nat.add(d, b))))