(* OK:  *)

(* Specifications: *)
Lemma distinct_edge_list_Br1:
forall(m:fmap)(x x' xs xs':dart)(l:list),
inv_hmap m -> planar m ->
pre_ring0 m (cons x x' (cons xs xs' l)) ->
distinct_edge_list (Br1 m x x') xs l.
Lemma pre_ring0_Br1_aux: forall(m:fmap)(x x':dart)(l:list),
inv_hmap m -> planar m ->
pre_ring0 m (cons x x' l) ->
pre_ring0 (Br1 m x x') l.