| n1 + m0 < # x, n0 < n1, ∀ n1, m0, x. n1 + m0 < # x ∧ n0 ≤ n1 → x = [] ∨ firstn(n0, restn(m0, x).rest) ⊑ firstn(n1, restn(m0, x).rest) ⊦ x = [], n1 = 0, firstn(n0, restn(m0, x).rest.rest) ⊑ firstn(n1 - 1, restn(m0, x).rest.rest) |
n1 = m + 1, n1 + m0 < # x, n0 < n1, ∀ n1, m0, x. n1 + m0 < # x ∧ n0 ≤ n1 → x = [] ∨ firstn(n0, restn(m0, x).rest) ⊑ firstn(n1, restn(m0, x).rest) ⊦ x = [], n1 = 0, firstn(n0, restn(m0, x).rest.rest) ⊑ firstn(m, restn(m0, x).rest.rest)
Used simplifier rules: n ≠ 0 ⊦ m = n - 1 ↔ n = m + 1; (elim) Used terms: n1, m