| reachable-1(H, r, r1), reachable-1(H, r1, r2), reachable-1(H, r2, r3), reachable-n(H, n0, r3, r0), ∀ H0, r4, r5. (∃ r6. reachable-1(H0, r4, r6) ∧ (∃ r1. reachable-1(H0, r6, r1) ∧ reachable-n(H0, n0, r1, r5))) ↔ (∃ x. path(x, H0) ∧ hd x = r4 ∧ x.last = r5 ∧ # x = 3 + n0) ⊦ ∃ x. path(x, H) ∧ hd x = r ∧ x.last = r0 ∧ # x = 4 + n0 |
reachable-1(H, r, r1), reachable-1(H, r1, r2), reachable-1(H, r2, r3), reachable-n(H, n0, r3, r0), (∃ r6. reachable-1(H, r1, r6) ∧ (∃ r1. reachable-1(H, r6, r1) ∧ reachable-n(H, n0, r1, r0))) ↔ (∃ x. path(x, H) ∧ hd x = r1 ∧ x.last = r0 ∧ # x = 3 + n0) ⊦ ∃ x. path(x, H) ∧ hd x = r ∧ x.last = r0 ∧ # x = 4 + n0
Used terms: H, r1, r0