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