Instance Perm_combiner : Perm_alg combiner.
Instance Sep_combiner: Sep_alg combiner.
Instance Disj_combiner {D1: Disj_alg A}: Disj_alg combiner.
(* Usefull facts about combiners *)

Lemma identity_combiner {C1: Canc_alg T1}: forall d : combiner,
identity d ->
d = CEmpty.