| reachable-n(H, (n + 1) + 1, r, H[r1].nxt), reachable-n(H, n, r, r2), reachable-1(H, r2, r1), r1 ∈ H, H[r1].nxt ∈ H, reachable-n(H, n + 2, r, H[r1].nxt) ⊦ H[r1].nxt = null, r1 = null, r2 ≠ null ∧ r2 ∈ H ∧ H[r2].nxt ≠ null ∧ H[H[r2].nxt].nxt ≠ null ∧ H[r2].nxt ∈ H ∧ H[H[r2].nxt].nxt ∈ H ∧ H[H[r2].nxt].nxt = H[r1].nxt |
⊦ reachable-1(H, r, r0) ↔ r ≠ null ∧ r0 ≠ null ∧ r ∈ H ∧ r0 ∈ H ∧ H[r].nxt = r0
Used terms: r1, r2, H