(*===========================================================
                expe AND bottom
============================================================*)

(* expo and between in an edge: *)

Definition expe(m:fmap)(z t:dart):=
  MA0.expo m z t.Definition betweene(m:fmap)(z v t:dart):=
  MA0.between m z v t.

Lemma exd_L_B_top_bot: forall(m:fmap)(k:dim)(x z:dart), exd m z <-> exd (L (B m k x) k (top m k x) (bottom m k x)) z.