Section PairCPO.
Variables (A B : cpo).
Local Notation tp := [poset of A * B].
Definition pair_bot : tp := (bot, bot).
Definition pair_lim (s : chain tp) : tp :=
(lim (proj1_chain s), lim (proj2_chain s)).

Lemma chain_clos_mono (s1 s2 : Pred T) :
s1 <=p s2 -> chain_closure s1 <=p chain_closure s2.