| x[m] = x[n], m < # x, n < # x ⊦ m = n, x = [], dups(x) |
(a + x0)[m] = (a + x0)[n], n < #(a + x0), m < #(a + x0), ∀ m, n. x0[m] = x0[n] ∧ m < # x0 ∧ n < # x0 → m = n ∨ x0 = [] ∨ dups(x0) ⊦ a + x0 = [], m = n, dups(a + x0)
Used simplifier rules: list freely generated by [], +;;