∀ a. # x0 < pos(a, x0) → pos(a, x0) = 0, #(a0 + x0) < pos(a, a0 + x0) ⊦ pos(a, a0 + x0) = 0
Used simplifier rules: pos-e: ⊦ pos(a, []) = 0;%list freely generated by [], +;;