(* Sewing two disconnected darts preserves planarity:*)

(* Specifications: *)
Lemma not_eqc_planar: forall (m:fmap)(k:dim)(x y:dart),
inv_qhmap m -> planar m ->  prec_Lq m k x y ->
let mc:= clos m in ~eqc mc x y ->
planar (L m k x y).