(* The following needs a hmap: *)

Lemma inv_hmap_l_13:
forall (m:fmap)(k:dim)(x y:dart),
inv_hmap m -> prec_lh m k x y ->
prec_Lq (L (B_1 (B m k x) k y) k x y)
k (A_1 m k y) (A m k x).