proposition: Lemma dorp2 : Dorp.dorp2 (@dorp).
proof: Proof. move=> A; rewrite /dorp /CRet (compA (Join \o M # swap)) -(compA Join). by rewrite (natural ret) (compA Join) joinretM compidf Hswap2. Qed.
imports: mathcomp(all_ssreflect) HB(structures) monae_lib hierarchy monad_lib