proposition: Lemma sdprod_Hall_p'coreP pi H G : pi^'.-Hall(G) 'O_pi^'(G) -> reflect ('O_pi^'(G) ><| H = G) (pi.-Hall(G) H).
proof: Proof. by rewrite -(pHallNK pi G H); apply: sdprod_Hall_pcoreP. 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)