| ∃ r0. reachable(r, r0, H) ∧ H[r0] .nxt = null, legal(H), r ∈ H, r ≠ null ⊦ ¬ cyclic(r, H) |
H[r0] .nxt = null, cyclic(r, H), reachable(r, r0, H), legal(H), r ∈ H, r0 ∈ H ⊦ r = null
[[CONCRETESIMPRULES : ([CSIMPFORWARD : ⊦ reachable(r, r1, H) → r1 ∈ H])]]