proposition: Lemma InPtUnE x k v f : valid (pts k v \+ f) -> x \In pts k v \+ f <-> x = (k, v) \/ x \In f.
proof: Proof. move=>W; split; last by case=>[->|/(InR W)]. by case/InUn; [case/InPt=>->; left|right]. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)