Bytes.len_app: def of bend-collections-laws-crypto@1.0.0.0
Import: import bend-collections-laws-crypto@1.0.0.0/proofs/crypto/secp256k1/bytes.bend as Bytes
Lines 89-94 of bend-collections-laws-crypto@1.0.0.0/proofs/crypto/secp256k1/bytes.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/crypto/secp256k1/bytes.bend&start_line=89&end_line=94

import Base

def len_app(xs: List<&2, U32>, +ys: List<&2, U32>) -> {List.length(&2, U32, List.append(&2, U32, xs, ys)) == Nat.add(List.length(&2, U32, xs), List.length(&2, U32, ys)) : Nat}:
  match xs:
    case Nil{}:
      {==}
    case +x <> +t:
      Equal.cong(Nat, Nat, n => 1n+n, List.length(&2, U32, List.append(&2, U32, t, ys)), Nat.add(List.length(&2, U32, t), List.length(&2, U32, ys)), len_app(t, ys))

Uses (7):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.cong
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.append
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.length
  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=U32