proposition: Lemma re_co_do_well_def : forall (X Z : CSetoid) (f : CSetoid_fun X Z), pred_wd Z (fun y : Z => {x : X | f x[=]y}).
proof: Proof. intros X Z f. unfold pred_wd in |- *. intros x y. intros H0 H1. elim H0. intros x0 H3. exists x0. astepr x. exact H3. Qed.
imports: CoRN.metrics.Prod_Sub