| n = n0 + # x, # x ≤ n ⊦ firstn(m, restn(n, x + y)) = firstn(m, restn(n0, y)) |
⊦ firstn(m, restn(n0 + # x, x + y)) = firstn(m, restn(n0, y))
Used simplifier rules: c: ⊦ m + n = n + m; from specification nat-basic%a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic% ⊦ m ≤ m + n; (s)