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