(** * [remove] *)

Fixpoint remove (k : key) (s : t elt) {struct s} : t elt :=
 match s with
  | nil => nil
  | (k',x) :: l =>
     match X.compare k k' with
      | LT _ => s
      | EQ _ => l
      | GT _ => (k',x) :: remove k l
     end
 end.

Lemma remove_3 : forall m (Hm:Sort m) x y e, MapsTo y e (remove x m) -> MapsTo y e m.