| a ∈ x0, n ≤ # x0, ∀ n0, a1. n0 < # x0 → (a1 ∈ x0 -1l n0 ↔ a1 ≠ x0[n0] ∧ a1 ∈ x0) ⊦ x0 = [], a = x0[n - 1], n = 0, a ∈ (a0 ' + x0) -1l n, a0 ∈ x0, dups(x0) |
n = m + 1, a ∈ x0, n ≤ # x0, ∀ n0, a1. n0 < # x0 → (a1 ∈ x0 -1l n0 ↔ a1 ≠ x0[n0] ∧ a1 ∈ x0) ⊦ x0 = [], a = x0[m], n = 0, a ∈ (a0 ' + x0) -1l n, a0 ∈ x0, dups(x0)
Used simplifier rules: n ≠ 0 ⊦ m = n - 1 ↔ n = m + 1; (elim) Used terms: n, m