proposition: Lemma omgidNeg (v : U) : ~~ last_atval false v = (omg v == nown).
proof: Proof. by rewrite (omgNeg _ id). Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq) pcm(options prelude pred) pcm(pcm morphism natmap)