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