| r ∈ H, legal(H) ⊦ r = null, cyclic(r, H), ∃ r0. reachable(r, r0, H) ∧ H[r0] .nxt = null |
⊦ cyclic(r, H) ↔ (∀ n. ∃ r0. reachable-n(H, n, r, r0))
r ∈ H, legal(H) ⊦ r = null, ∀ n. ∃ r0. reachable-n(H, n, r, r0), ∃ r0. reachable(r, r0, H) ∧ H[r0] .nxt = null
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (H, r)]]