proposition: Lemma dom_ordfresh h x : x \in dom h -> x < fresh h.
proof: Proof. by move/lastkey_max. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)