proposition: Lemma hull0 : hull set0 = set0 :> set A.
proof: Proof. rewrite funeqE => d; rewrite propeqE; split => //. move=> [n [g [e [gX ->{d}]]]]. destruct n as [|n]; first by move: (fdistI0_False e). exfalso; apply: (gX (g ord0)); exact/imageP. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg fingroup perm matrix) mathcomp(mathcomp_extra boolp classical_sets Rstruct) mathcomp(ssrnum ereal) mathcomp(lra Rstruct reals) Reals ssrR Reals_ext Ranalysis_ext ssr_ext ssralg_ext logb realType_ext fdist