proposition: Lemma atvalUn v t h1 h2 : valid (h1 \+ h2) -> t <= last_key h1 -> (forall k : nat, k \in dom h2 -> last_key h1 < k) -> atval v t (h1 \+ h2) = atval v t h1.
proof: Proof. move=>V K H; rewrite /atval findUnR //. by case: ifP=>// /H; rewrite ltnNge K. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)