(** Results about [lt_tree] and [gt_tree] *)

(* Specifications: *)
Lemma lt_leaf : forall x, lt_tree x (Leaf elt).
Lemma gt_leaf : forall x, gt_tree x (Leaf elt).
Lemma lt_tree_node : forall x y l r e h,
lt_tree x l -> lt_tree x r -> X.lt y x -> lt_tree x (Node l y e r h).
Lemma gt_tree_node : forall x y l r e h,
gt_tree x l -> gt_tree x r -> X.lt x y -> gt_tree x (Node l y e r h).