(* REMARK: SYMMETRY OF expf in the closure NOT USED *)
(* ========================================================== PLANARITY CRITERIA (SUFFICIENT CONDITIONS) =============================================================*)
(* Sewing at dimension 0: *)

Lemma expf_planar_0: forall (m:fmap)(x y:dart),
inv_qhmap m -> planar m ->
prec_Lq m di0 x y -> let mc:= clos m in
expf mc (A_1 mc di1 x) y ->
planar (L m di0 x y).