Definition planar(m:fmap):= genus m = 0.

Lemma expf_planar_L1: forall (m:fmap)(x y:dart), inv_qhmap m -> planar m -> prec_Lq m di1 x y -> let mc:= clos m in (~eqc mc x y \/ expf mc x (A mc di0 y)) -> planar (L m di1 x y).