proposition: Lemma le0_cp x : x <= 0 -> (0 <= - x) * (x <= - x).
proof: Proof. by move=> hx; rewrite oppr_cp0 hx (@le_trans _ _ 0) ?oppr_cp0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)