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