| (r ' + x1)[m] = r, path(r ' + x1, H), m ≤ # x1 ⊦ x1 = [], m = 0, reachable-n(H, m, r, r) |
⊦ n ≠ 0 → (reachable-n(H, n, r, r0) ↔ (∃ x. path(x, H) ∧ hd x = r ∧ x .last = r0 ∧ # x = n + 1))
m ≠ 0 → (reachable-n(H, m, r, r) ↔ (∃ x. path(x, H) ∧ hd x = r ∧ x .last = r ∧ # x = m + 1)), (r ' + x1)[m] = r, path(r ' + x1, H), m ≤ # x1 ⊦ x1 = [], m = 0, reachable-n(H, m, r, r)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (m, H, r, r)]]