proposition: Lemma ltr_normlP x y : reflect ((-x < y) * (x < y)) (`|x| < y).
proof: Proof. exact: real_ltr_normlP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)