proposition: Lemma normr_nneg (R : numDomainType) (x : R) : `|x| \is Num.nneg.
proof: Proof. by rewrite qualifE /=. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)