proposition: Lemma sdprodWC A B G : A ><| B = G -> B * A = G.
proof: Proof. by move/sdprodWpp/pprodWC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)