def len_append

bend-collections-laws-crypto@1.0.0.0 · proofs/crypto/argon2/password.bend:31

import Base

31def len_append(+a: List<&2, U32>, +b: List<&2, U32>) -> {len(List.append(&2, U32, a, b)) == Nat.add(len(a), len(b)) : Nat}:
32  match a:
33    case Nil{}:
34      {==}
35    case +x <> +r:
36      Equal.cong(Nat, Nat, z => 1n+z, len(List.append(&2, U32, r, b)), Nat.add(len(r), len(b)), len_append(r, b))