proposition: Lemma pHall_pgroup pi A B : pi.-Hall(A) B -> pi.-group B.
proof: Proof. by case/and3P. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)