| adr ∈ as, ∀ as0. # as0 < # as → true → (0 = as0.size ↔ (∀ adr. adr ∈ as0 → adr.size = 0)) ⊦ # as = 0, 0 = as.size ↔ (∀ adr. adr ∈ as → adr.size = 0) |
⊦ adr ∈ as ↔ (∃ as0. as = as0 ++ adr ∧ ¬ adr ∈ as0)
∃ as0. as = as0 ++ adr ∧ ¬ adr ∈ as0, ∀ as0. # as0 < # as → true → (0 = as0.size ↔ (∀ adr. adr ∈ as0 → adr.size = 0)) ⊦ # as = 0, 0 = as.size ↔ (∀ adr. adr ∈ as → adr.size = 0)
Used terms: as, adr