proposition: Lemma image_const A B (X : neset A) (b : B) : (fun _ => b) @` X = [set b].
proof: Proof. rewrite eqEsubset; split=> b'; [by case => ? _ -> | by move=> ?; eexists]. Qed.
imports: HB(structures) Reals mathcomp(all_ssreflect ssralg ssrnum) mathcomp(mathcomp_extra boolp classical_sets Rstruct reals) mathcomp(finmap) Reals_ext realType_ext classical_sets_ext ssrR fdist fsdist convex