(* 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_constant (T: Set) (f: T -> nat) (c: nat) (t: ne_tree_monad.M T): (forall x, ne_tree.In x t -> f x = c) -> expec f t = INR c.