(* SYMMETRICALLY: *)

(* Specifications: *)
Lemma cA0_1_Br1:forall(m:fmap)(x x' z:dart),
inv_hmap m -> double_link m x x' ->
cA_1 (Br1 m x x') zero z =
if eq_dart_dec (cA m zero x) z then x'
else if eq_dart_dec (cA m zero x') z then x
else cA_1 m zero z.
Lemma cA1_Br1:forall(m:fmap)(x x' z:dart),
inv_hmap m ->
cA (Br1 m x x') one z = cA m one z.
Lemma cA1_1_Br1:forall(m:fmap)(x x' z:dart),
inv_hmap m ->
cA_1 (Br1 m x x') one z = cA_1 m one z.