/// <summary>
/// Computes the sum of two double double numbers.
/// </summary>
/// <param name="x">The first number.</param>
/// <param name="y">The second number.</param>
/// <returns>The value of <paramref name="x"/> + <paramref name="y"/>.</returns>
public static DoubleDouble operator +(DoubleDouble x, DoubleDouble y)
{
// Add high components
ExtendedMath.TwoSum(x.hi, y.hi, out double sHi, out double sLo);
if (ExtendedMath.IsNotFinite(sHi))
{
return((DoubleDouble)sHi);
}
// Add low components
ExtendedMath.TwoSum(x.lo, y.lo, out double tHi, out double tLo);
ExtendedMath.TwoSum(sHi, sLo + tHi, out double vHi, out double vLo);
ExtendedMath.FastTwoSum(vHi, tLo + vLo, out double zHi, out double zLo);
return(new DoubleDouble(zHi, zLo));
}
/// <summary>
/// Computes the sum of two double double numbers.
/// </summary>
/// <param name="a">The first number.</param>
/// <param name="b">The second number.</param>
/// <returns>The value of <paramref name="a"/> + <paramref name="b"/>.</returns>
public static DoubleDouble operator +(DoubleDouble a, DoubleDouble b)
{
// Add high components
double sHi, sLo;
ExtendedMath.TwoSum(a.hi, b.hi, out sHi, out sLo);
// Add low components
double tHi, tLo;
ExtendedMath.TwoSum(a.lo, b.lo, out tHi, out tLo);
double vHi, vLo;
ExtendedMath.TwoSum(sHi, sLo + tHi, out vHi, out vLo);
double zHi, zLo;
ExtendedMath.FastTwoSum(vHi, tLo + vLo, out zHi, out zLo);
return(new DoubleDouble(zHi, zLo));
}