proposition: Lemma ojoinA x y z : obind (ojoin x) (ojoin y z) = obind (ojoin^~ z) (ojoin x y).
proof: Proof. by rewrite /obind/ojoin /= addnA. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype) pcm(options prelude) pcm(pcm morphism)