Definition empty : t := mk (M.empty elt) wf_empty.

(* Specifications: *)
Lemma repr_empty:
forall a, repr empty a = a.
Lemma sameclass_empty:
forall a b, sameclass empty a b -> a = b.
Lemma repr_empty:
forall a, repr empty a = a.
Lemma sameclass_empty:
forall a b, sameclass empty a b -> a = b.