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