(* The coercion to rel must be explicit for derived Notations to unparse. *)
Notation coerced_frel f := (rel_of_simpl_rel (frel f)) (only parsing).Notation "x |-> y" := (FunDelta x y)
  (at level 190, no associativity,
   format "'[hv' x '/ '  |->  y ']'") : fun_delta_scope.Notation "[ 'eta' f 'with' d1 , .. , dn ]" :=
  (SimplFunDelta (fun _ =>
     app_fdelta d1%FUN_DELTA .. (app_fdelta dn%FUN_DELTA f) ..))
  (at level 0, format
  "'[hv' [ '[' 'eta' '/ '  f ']' '/'  'with'  '[' d1 , '/'  .. , '/'  dn ']' ] ']'"
  ) : fun_scope.Definition comparable := forall x y : T, decidable (x = y).Definition compareb x y : bool := compare_T x y.

Lemma compareP : Equality.axiom compareb.