proposition: Lemma valid_umfiltUnR f1 f2 p : valid (f1 \+ f2) -> valid (f1 \+ um_filter p f2).
proof: Proof. by rewrite !(joinC f1); apply: valid_umfiltUnL. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)