proposition: Lemma umall2Unf f f1 f2 : Reflexive P -> valid f1 = valid f2 -> um_all2 f1 f2 -> um_all2 (f1 \+ f) (f2 \+ f).
proof: Proof. by rewrite -!(joinC f); apply: umall2fUn. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)