proposition: Lemma InPt x k v : x \In pts k v -> x = (k, v) /\ C k.
proof: Proof. by case: x=>a b /In_find; rewrite findPt2; case: ifP=>//; case/andP=>/eqP ->-> [->]. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)