proposition: Lemma lteif_normr C x y : (x < `|y| ?<= if C) = (x < y ?<= if C) || (x < - y ?<= if C).
proof: Proof. by case: C; rewrite /= lter_normr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)