* #transform} methods all return {@link Double#NaN}. The {@link #inverse} method returns the same
   * instance.
   */
  public static LinearTransformation forNaN() {
    return NaNLinearTransformation.INSTANCE;
  }

  /** Returns whether this is a vertical transformation. */
  public abstract boolean isVertical();

   *
   * <p>If the dataset contains any non-finite values ({@link Double#POSITIVE_INFINITY}, {@link
   * Double#NEGATIVE_INFINITY}, or {@link Double#NaN}) then the result is {@link
   * LinearTransformation#forNaN()}.
   *
   * @throws IllegalStateException if the dataset is empty or contains a single pair of values, or
   *     both the {@code x} and {@code y} dataset have zero population variance
   */

   *
   * <p>If the dataset contains any non-finite values ({@link Double#POSITIVE_INFINITY}, {@link
   * Double#NEGATIVE_INFINITY}, or {@link Double#NaN}) then the result is {@link
   * LinearTransformation#forNaN()}.
   *
   * @throws IllegalStateException if the dataset is empty or contains a single pair of values, or
   *     both the {@code x} and {@code y} dataset must have zero population variance
   */

    assertThrows(IllegalArgumentException.class, () -> LinearTransformation.horizontal(Double.NaN));
  }

  public void testForNaN() {
    LinearTransformation transformation = LinearTransformation.forNaN();
    assertLinearTransformationNaN(transformation);
  }

    assertThrows(IllegalArgumentException.class, () -> LinearTransformation.horizontal(Double.NaN));
  }

  public void testForNaN() {
    LinearTransformation transformation = LinearTransformation.forNaN();
    assertLinearTransformationNaN(transformation);
  }

	FormatGNU

	// Schily's tar format, which is incompatible with USTAR.
	// This does not cover STAR extensions to the PAX format; these fall under
	// the PAX format.
	formatSTAR

	formatMax
)

func (f Format) has(f2 Format) bool   { return f&f2 != 0 }
func (f *Format) mayBe(f2 Format)     { *f |= f2 }
func (f *Format) mayOnlyBe(f2 Format) { *f &= f2 }
func (f *Format) mustNotBe(f2 Format) { *f &^= f2 }

func TestFormatErasureEmpty(t *testing.T) {
	format := newFormatErasureV3(1, 16)
	format.Erasure.DistributionAlgo = formatErasureVersionV2DistributionAlgoV1
	formats := make([]*formatErasureV3, 16)

	for j := range 16 {
		newFormat := format.Clone()
		newFormat.Erasure.This = format.Erasure.Sets[0][j]
		formats[j] = newFormat
	}

	// empty format to indicate disk not found, but this
	// empty should return false.

	format := &formatErasureV3{}
	format.Version = formatMetaVersionV1
	format.Format = formatBackendErasure
	if setLen == 1 {
		format.Format = formatBackendErasureSingle
	}
	format.ID = mustGetUUID()
	format.Erasure.Version = formatErasureVersionV3
	format.Erasure.DistributionAlgo = formatErasureVersionV3DistributionAlgoV3
	format.Erasure.Sets = make([][]string, numSets)

)

// Valid - tells us if the format is sane by validating
// format version and erasure coding information.
func (m *xlMetaV1Object) valid() bool {
	return isXLMetaFormatValid(m.Version, m.Format) &&
		isXLMetaErasureInfoValid(m.Erasure.DataBlocks, m.Erasure.ParityBlocks)
}

// Verifies if the backend format metadata is sane by validating
// the version string and format style.

		case "Version":
			z.Version, err = dc.ReadString()
			if err != nil {
				err = msgp.WrapError(err, "Version")
				return
			}
		case "Format":
			z.Format, err = dc.ReadString()
			if err != nil {
				err = msgp.WrapError(err, "Format")
				return
			}
		case "Stat":
			err = z.Stat.DecodeMsg(dc)
			if err != nil {
				err = msgp.WrapError(err, "Stat")
				return
			}