proposition: Lemma restr_un_op_wd : un_op_wd Build_SubCSetoid restr_un_op.
proof: Proof. intros x y. case y. case x. intros. now apply: (csf_wd _ _ f). Qed.
imports: CoRN.tactics.CornTac CoRN.logic.CLogic CoRN.tactics.Step CoRN.algebra.RSetoid