proposition: Lemma lee_abs_add x y : `|x + y| <= `|x| + `|y|.
proof: Proof. by move: x y => [x| |] [y| |] //; rewrite /abse -EFinD lee_fin ler_normD. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed