proposition: Lemma umcnt_leUn A p (h1 h2 : natmap A) t : valid (h1 \+ h2) -> t <= last_key h1 -> {in dom h2, forall k, k > last_key h1} -> um_count (predI p (le t)) (h1 \+ h2) = um_count (predI p (le t)) h1.
proof: Proof. by move=>V K D; rewrite -!umcnt_umfilt umfilt_leUn. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)