m ≤ n, n ≤ # x, m ≤ # x ⊦ restn(m, firstn(n, x)) = firstn(n - m, restn(m, x))
Used simplifier rules: let: ⊦ n ≤ n0 ∧ n0 ≤ n1 → n ≤ n1; (forward) from specification nat