| reach(source, a, n0), b ∈ succ(a) ⊦ succ(a) = ∅, # succ(a) = 0, reach<(source, b, n0 + 2) |
⊦ reach<(a, b, n) ↔ (∃ m. m < n ∧ reach(a, b, m))
reach(source, a, n0), b ∈ succ(a) ⊦ succ(a) = ∅, # succ(a) = 0, ∃ m. m < n0 + 2 ∧ reach(source, b, m)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (n0 + 2, b, source)]]