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