proposition: Lemma ordfresh_dom h t : fresh h <= t -> t \notin dom h.
proof: Proof. by rewrite leqNgt; apply: contra; apply: dom_ordfresh. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)