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