∀ m. m < # x0 → x0 to m + 1 = (x0 to m) + x0[m] ' ∨ x0 = [], m < #(a + x0) ⊦ a + x0 to m + 1 = (a + x0 to m) + (a + x0)[m] ', a + x0 = []
Used simplifier rules: list freely generated by [], +;;