proposition: Lemma mor_vee_cat_ex : forall u, mor vee_cat u = (exists y:morsy vee_data, u = catyd_arrow y).
proof: Proof. ir. ap iff_eq; ir. ufi vee_cat H; rwi mor_catyd H. am. ap vee_data_property. nin H. rw H. ap mor_vee_cat. Qed.
imports: Arith cat_examples cardinal fc_limits