Definition is_effective {C : category} {x : C} (R : internal_eqrel x) : UU := ∑ (Coeq : Coequalizer (internal_relation_src R) (internal_relation_tar R)), isPullback (CoequalizerEqAr Coeq).
Require Import UniMath.Foundations.All. Require Import UniMath.MoreFoundations.All. Require Import UniMath.CategoryTheory.Core.Prelude. Require Import UniMath.CategoryTheory.Limits.Pullbacks. Require Import UniMath.CategoryTheory.Limits.Coequalizers. Require Import UniMath.CategoryTheory.RegularAndExact.RegularCategory.