proposition: Lemma le_Taggedr x (u : T' (tag x)) : (x <= Tagged T' u) = (tagged x <= u).
proof: Proof. by case: x => [t v]/= in u *; rewrite leEsig/= lexx/= tagged_asE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)