Section char.
Variables (n : nat) (gT rT : finGroupType) (D G : {group gT}).
Fact abelian_type_subproof G :
{H : {group gT} & abelian G -> {x | #[x] = exponent G & <[x]> \x H = G}}.
Fixpoint abelian_type_rec n G :=
if n is n'.+1 then if abelian G && (G :!=: 1) then
exponent G :: abelian_type_rec n' (tag (abelian_type_subproof G))
else [::] else [::].
Definition abelian_type (A : {set gT}) := abelian_type_rec #|A| <<A>>.
Definition homocyclic A := abelian A && constant (abelian_type A).

Lemma exponent_dprod_homocyclic p K H G :
K \x H = G -> p.-group G -> homocyclic G -> K :!=: 1 ->
exponent K = exponent G.