(*=========================================================== expe, betweene_dec, between_bottom_B0 AND MA0.between_dec ============================================================*)
(* Decidability of betweene, in Prop: *)

Lemma betweene_dec1: forall(m:fmap)(z v t:dart),
inv_hmap m -> exd m z -> exd m v ->
(betweene m z v t \/ ~betweene m z v t).