law length_append

bend-mathlib@0.8.1.0 · string.bend:61

import Base

61# The length of an append is the sum of the lengths.
62law length_append:
63  for a: String
64  for -b: String
65  {String.length(String.append(a, b)) == Nat.add(String.length(a), String.length(b)) : Nat}