| n < m, m ≤ # x ⊦ firstn(m, x)[n] = x[n] |
n < m, n < # x, m ≤ # x ⊦ firstn(m, x)[n] = x[n], x = []
Used simplifier rules: ⊦ # x = 0 ↔ x = []; (s)% ⊦ m < n → n ≠ 0; (s)%fle: ⊦ m < n ∧ n ≤ n0 → m < n0; (forward) from specification nat%f: ⊦ m < n → n ≠ 0; (forward) from specification nat-basic