| r ∈ H, reachable(r, r2, H[r2, ce]) ⊦ r2 ∈ H, ∃ r0. reachable(r, r0, H) ∧ H[r0].nxt = r2 ∧ H[r0].nxt ≠ null |
⊦ reachable(r, r0, H) ↔ (∃ x. path(r ' + x, H) ∧ (r ' + x).last = r0 ∧ ¬ dups(r ' + x))
r ∈ H, ∃ x. path(r ' + x, H[r2, ce]) ∧ (r ' + x).last = r2 ∧ ¬ dups(r ' + x) ⊦ r2 ∈ H, ∃ r0. reachable(r, r0, H) ∧ H[r0].nxt = r2 ∧ H[r0].nxt ≠ null
Used terms: H[r2, ce], r2, r