(*========================================================= cF / L, expf / L, CNS ===========================================================*)
(* expf IS AN EQUIVALENCE (NEW PLACE): *)

Lemma Iter_cF_I:forall(m:fmap)(x z:dart)(u:tag)(p:point)(i:nat),
inv_hmap m -> prec_I m x ->
exd m z -> x <> z ->
Iter (cF (I m x u p)) i z = Iter (cF m) i z.