| firstn(n, a ' + y) = a0 ' + y0 ⊦ a0 = a, n = 0 |
⊦ n ≠ 0 → firstn(n, a ' + x) = a ' + firstn(n -1, x)
Used simplifier rules: ⊦ n -1 = n - 1; (s)% ⊦ a ' + x = b ' + y ↔ a = b ∧ x = y; (ws)%a: ⊦ (x + y) + z = x + y + z; from specification list Used terms: y, a, n