(*Definition Mmake {A B:Type} (f:A→B) x:= Mreturn (f x).*)
Definition Mupdate (f:nat→nat) := (λ st, ((f st),tt)):monad unit.

Lemma lt_lt_Mmap2_lt {A B C:Type} (f:A→B→C) (ma:monad A) (mb:monad B):
Mlt ma → Mlt mb → Mlt (Mmap2 f ma mb).