| n < # x ⊦ a ∈ x -1l n ↔ a ≠ x[n] ∧ a ∈ x, x = [], dups(x) |
∀ n, a. n < # x0 → (a ∈ x0 -1l n ↔ a ≠ x0[n] ∧ a ∈ x0) ∨ x0 = [] ∨ dups(x0), n < #(a0 + x0) ⊦ a ∈ (a0 + x0) -1l n ↔ a ≠ (a0 + x0)[n] ∧ a ∈ a0 + x0, a0 + x0 = [], dups(a0 + x0)
Used simplifier rules: list freely generated by [], +;;