proposition: Lemma numNEsign x : -x = (-1) ^+ (0 < x)%R * `|x|.
proof: Proof. by rewrite -realNEsign. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)