⊦ as ⊆ as0 ↔ (∀ adr. adr ∈ as → adr ∈ as0)
union(asar, 0, # asar) = as -- adr, n < # asar ⊦ ∀ adr. adr ∈ asar[n] → adr ∈ as
Used terms: as, asar[n]