| path(r ' + x, H), reachable((r ' + x).last, r1, H), r1 ∈ H, (r ' + x).last ∈ H ⊦ reachable(r, r1, H) |
path(r ' + (r0 + x0), H), reachable((r ' + (r0 + x0)).last, r1, H), (r ' + (r0 + x0)).last ∈ H, r1 ∈ H, ∀ r, H, r1. path(r ' + x0, H) ∧ reachable((r ' + x0).last, r1, H) ∧ r1 ∈ H ∧ (r ' + x0).last ∈ H → reachable(r, r1, H) ⊦ reachable(r, r1, H)
Used simplifier rules: path-one: ⊦ path(r ', H) ↔ r ∈ H ∧ r ≠ null;%reflist freely generated by [], +;;% ⊦ x0 + [] = x0; (s)%a: ⊦ (x0 + x1) + x2 = x0 + x1 + x2; from specification list[reflist]% ⊦ r '.last = r; (s)