proposition: Lemma umcompPtUnf g f k v : valid (pts k v \+ g) -> um_comp (pts k v \+ g) f = omap (fun x => if x.2 == k then Some v else None) f \+ um_comp g f.
proof: Proof. by move=>W; rewrite umcompUnf // umcompPtf (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)