(* 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_ext (T: Set) (f g: T -> nat) (e: ext_eq f g): forall x, expec f x = expec g x.