∀ H, r. path(x0, H) → path(x0, H -- r) ∨ r ∈ x0, path(r0 + x0, H) ⊦ path(r0 + x0, H -- r), r ∈ r0 + x0
Used simplifier rules: path-empty: ⊦ ¬ path([], H);%reflist freely generated by [], +;;