| legal(H), r ∈ H, reachable-n(H, n0, r, r0) ⊦ r = null, ∃ r0. reachable(r, r0, H) ∧ H[r0] .nxt = null, reachable-n(H, n0 + 1, r, H[r0] .nxt) |
⊦ reachable-n(H, n + 1, r, r0) ↔ (∃ r1. reachable-n(H, n, r, r1) ∧ reachable-1(H, r1, r0))
legal(H), r ∈ H, reachable-n(H, n0, r, r0) ⊦ r = null, ∃ r0. reachable(r, r0, H) ∧ H[r0] .nxt = null, ∃ r1. reachable-n(H, n0, r, r1) ∧ reachable-1(H, r1, H[r0] .nxt)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (H[r0] .nxt, r, n0, H)]]