proposition: Lemma lee0_abs x : x <= 0 -> `|x| = - x.
proof: Proof. by move: x => [x| |]//; rewrite lee_fin => x0; apply/eqP; rewrite eqe ler0_norm. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed