(* misc expec *)

Add Parametric Morphism (A: Set): (@expec A)
  with signature (@ext_eq A nat) ==> (@ext_eq (ne_tree.T A) R)
  as expec_ext_morph.

Lemma expec_nonneg (T: Set) (m: ne_tree_monad.M T) (f: T -> nat): 0 <= expec f m.