| ⊦ disj(T1, T2) → ( ¬ disj(T3, T4) ↔ ¬ (∀ n, m. (n < # T1 ∧ m < # T2 ∧ T1[n] ≠ empty ∧ T2[m] ≠ empty → T1[n].elem ≠ T2[m].elem) → n < # T3 ∧ m < # T4 ∧ T3[n] ≠ empty ∧ T4[m] ≠ empty → T3[n].elem ≠ T4[m].elem)) |
disj(T1, T2) ⊦ ¬ disj(T3, T4) ↔ (∃ n, m. ¬ ( (n < # T1 ∧ m < # T2 ∧ T1[n] ≠ empty ∧ T2[m] ≠ empty → T1[n].elem ≠ T2[m].elem) → n < # T3 ∧ m < # T4 ∧ T3[n] ≠ empty ∧ T4[m] ≠ empty → T3[n].elem ≠ T4[m].elem))
[Concretesimprules(())]