#[global]
Instance rbal'_ok l x r `(Ok l, Ok r, lt_tree x l, gt_tree x r) :
Ok (rbal' l x r).
Global Hint Rewrite In_node_iff In_leaf_iff
makeRed_spec makeBlack_spec lbal_spec rbal_spec rbal'_spec : rb.
Ltac descolor := destruct_all Color.t.
Ltac destree t := destruct t as [|[|] ? ? ?].
Ltac autorew := autorewrite with rb.
Tactic Notation "autorew" "in" ident(H) := autorewrite with rb in H.
(** ** Insertion *)

Lemma ins_spec : forall s x y,
InT y (ins x s) <-> X.eq y x \/ InT y s.