proposition: Lemma eq_cardT (A : {pred T}) : A =i predT -> #|A| = size (enum T).
proof: Proof. by move=> /eq_enum<-; rewrite cardE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)