| reachable(r, r0, H), r0 ∈ H, r ∈ H ⊦ H[r].nxt = null, r = r0, r = null, H[r].nxt ∈ H |
⊦ reachable(r, r0, H) ↔ (∃ x. path(r ' + x, H) ∧ (r ' + x).last = r0)
r ∈ H, r0 ∈ H, ∃ x. path(r ' + x, H) ∧ (r ' + x).last = r0 ⊦ H[r].nxt = null, r = null, r = r0, H[r].nxt ∈ H
Used terms: H, r0, r