fact: Definition is_least_upperbound (x : X) : hProp := (is_upperbound x ∧ ∀ (y : X), is_upperbound y ⇒ PX x y)%logic.
imports: UniMath.MoreFoundations.All UniMath.OrderTheory.Posets.Basics UniMath.OrderTheory.Posets.MonotoneFunctions UniMath.OrderTheory.Posets.PointedPosets UniMath.OrderTheory.DCPOs.Core.DirectedSets