1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 include "ground/notation/functions/powerclass_1.ma".
16 include "ground/notation/relations/epsilon_3.ma".
17 include "ground/lib/relations.ma".
19 (* SUBSETS ******************************************************************)
21 definition subset (A): Type[0] ≝
25 "power class (subset)"
26 'PowerClass A = (subset A).
28 definition subset_in (A): 𝒫❨A❩ → 𝒫❨A❩ ≝
33 'Epsilon A a u = (subset_in A u a).