proposition: Lemma add_algA : associative add_alg.
proof: Proof. elim/quotW=> x; elim/quotW=> y; elim/quotW=> z; rewrite !piE -equiv_alg. by apply: eq_crealP; exists m0=> * /=; rewrite addrA subrr normr0. Qed.
imports: HB(structures) mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(bigop order ssralg ssrnum ssrint rat poly polydiv polyorder) mathcomp(perm matrix mxpoly polyXY binomial generic_quotient) mathcomp(cauchyreals separable zmodp bigenough)