proposition: Lemma ler0_def x : (x <= 0) = (`|x| == - x).
proof: Proof. by rewrite ler_def sub0r normrN. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)