proposition: Lemma umcnt_undef p : um_count p undef = 0.
proof: Proof. by rewrite /um_count umfilt_undef dom_undef. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)