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