proposition: Lemma inversePtUn k v f : valid (pts k v \+ f) -> inverse (pts k v \+ f) = pts v k \+ inverse f.
proof: Proof. by move=>W; rewrite inverseUn // inversePt // (validPtUn_cond W). Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)