Section CompAct.
Variables (gT : finGroupType) (G : {group gT}) (f : {morphism G >-> aT}).

(* Specifications: *)
Lemma comp_is_groupAction : is_groupAction R (comp_action to f).
Canonical comp_groupAction := GroupAction comp_is_groupAction.
Lemma gacent_comp U : 'C_(|comp_groupAction)(U) = 'C_(|to)(f @* U).
End CompAct.