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