0 < # x ⊦ x[0, x[0]] = x, x = []
∀ x. n0 < # x → x[n0, x[n0]] = x ∨ x = [], n0 +1 < # x ⊦ x[n0 +1, x[n0 +1]] = x, x = []
Used simplifier rules: nat freely generated by 0, +1;;