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