∀ r, H. x0.last = null ∧ path(r ' + x0, H) ∧ null ∈ H → x0 = [], (r0 + x0).last = null, path(r ' + (r0 + x0), H), null ∈ H ⊦ r0 + x0 = []
Used simplifier rules: reflist freely generated by [], +;;