(*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 Mnew_fun_mono: Mmono Mnew_fun.
Definition Mmap2 {A B C:Type} (f:A→B→C) (ma:monad A) (mb:monad B):=
(λ s0, let (s1,a) := ma s0 in let (s2,b) := mb s1 in (s2,(f a b))):monad C.