proposition: Lemma umpleq_undef x : [pcm x <= undef].
proof: Proof. by exists undef; rewrite join_undef. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)