| n + n0 + n1 ≤ #(a + x0), ∀ n, n0, n1. n + n0 + n1 ≤ # x0 → firstn(n0, restn(n, x0)) + firstn(n1, restn(n + n0, x0)) = firstn(n0 + n1, restn(n, x0)) ⊦ firstn(n0, restn(n, a + x0)) + firstn(n1, restn(n + n0, a + x0)) = firstn(n0 + n1, restn(n, a + x0)) |
n + n0 + n1 ≤ 1 + # x0, ∀ n, n0, n1. n + n0 + n1 ≤ # x0 → firstn(n0, restn(n, x0)) + firstn(n1, restn(n + n0, x0)) = firstn(n0 + n1, restn(n, x0)) ⊦ firstn(n0, restn(n, a ' + x0)) + firstn(n1, restn(n + n0, a ' + x0)) = firstn(n0 + n1, restn(n, a ' + x0))
Used simplifier rules: a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ # a ' = 0 +1; (s)% ⊦ #(x + y) = # x + # y; (s)% ⊦ a + x = a ' + x; (s)