proposition: Lemma ler_normlP x y : reflect ((- x <= y) * (x <= y)) (`|x| <= y).
proof: Proof. exact: real_ler_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)