proposition: Lemma lastatval_indom v h : last_atval v h <> v -> last_key h \in dom h.
proof: Proof. by rewrite /last_atval /atval; case: dom_find=>// ->. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)