proposition: Fact equiv_subfext_is_equiv : equiv_class_of equiv_subfext.
proof: Proof. by rewrite /equiv_subfext; split=> x // y w /eqP->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop ssralg countalg) mathcomp(finalg zmodp matrix vector falgebra poly polydiv) mathcomp(mxpoly generic_quotient)