public static float NextDown(this float value)
{
if (float.IsNaN(value) || value == float.NegativeInfinity)
{
return(value);
}
else
{
if (value == 0.0f)
{
return(-float.MinValue);
}
else
{
return(BitConversion.Int32BitsToSingle(BitConversion.SingleToRawInt32Bits(value) +
((value > 0.0f) ? -1 : +1)));
}
}
}
public static double NextDown(this double value)
{
if (double.IsNaN(value) || value == double.NegativeInfinity)
{
return(value);
}
else
{
if (value == 0.0)
{
return(-double.MinValue);
}
else
{
return(BitConversion.Int64BitsToDouble(BitConversion.DoubleToRawInt64Bits(value) +
((value > 0.0d) ? -1L : +1L)));
}
}
}
public void Test_DoubleToInt64Bits_NegativeInfinity()
{
assertTrue("Bad conversion for -infinity.", BitConversion.DoubleToInt64Bits(double.NegativeInfinity) == unchecked ((long)0xfff0000000000000L));
}
public void Test_DoubleToInt64Bits_PositiveInfinity()
{
assertTrue("Bad conversion for +infinity.", BitConversion.DoubleToInt64Bits(double.PositiveInfinity) == 0x7ff0000000000000L);
}
public void Test_SingleToInt32Bits_NegativeInfinity()
{
assertTrue("Bad conversion for -infinity.", BitConversion.SingleToInt32Bits(float.NegativeInfinity) == unchecked ((int)0xFF800000));
}
public void Test_SingleToInt32Bits_PositiveInfinity()
{
assertTrue("Bad conversion for +infinity.", BitConversion.SingleToInt32Bits(float.PositiveInfinity) == 0x7F800000);
}
public static float NextAfter(this float start, double direction)
{
/*
* The cases:
*
* NextAfter(+infinity, 0) == MaxValue
* NextAfter(+infinity, +infinity) == +infinity
* NextAfter(-infinity, 0) == -MaxValue
* NextAfter(-infinity, -infinity) == -infinity
*
* are naturally handled without any additional testing
*/
// First check for NaN values
if (float.IsNaN(start) || double.IsNaN(direction))
{
// return a NaN derived from the input NaN(s)
return(start + (float)direction);
}
else if (start == direction)
{
return((float)direction);
}
else
{ // start > direction or start < direction
// Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0)
// then bitwise convert start to integer.
int transducer = BitConversion.SingleToRawInt32Bits(start + 0.0f);
/*
* IEEE 754 floating-point numbers are lexicographically
* ordered if treated as signed- magnitude integers .
* Since .NET's integers are two's complement,
* incrementing" the two's complement representation of a
* logically negative floating-point value *decrements*
* the signed-magnitude representation. Therefore, when
* the integer representation of a floating-point values
* is less than zero, the adjustment to the representation
* is in the opposite direction than would be expected at
* first.
*/
if (direction > start)
{// Calculate next greater value
transducer = transducer + (transducer >= 0 ? 1 : -1);
}
else
{ // Calculate next lesser value
Debug.Assert(direction < start);
if (transducer > 0)
{
--transducer;
}
else
if (transducer < 0)
{
++transducer;
}
/*
* transducer==0, the result is -MinValue
*
* The transition from zero (implicitly
* positive) to the smallest negative
* signed magnitude value must be done
* explicitly.
*/
else
{
transducer = SingleSignBitMask | 1;
}
}
return(BitConversion.Int32BitsToSingle(transducer));
}
}
public static bool IsNegativeZero(this double d)
{
return(d == 0 && BitConversion.DoubleToRawInt64Bits(d) == BitConversion.DoubleToRawInt64Bits(NegativeZero));
}
public static bool IsNegativeZero(this float f)
{
return(f == 0 && BitConversion.SingleToRawInt32Bits(f) == BitConversion.SingleToRawInt32Bits(NegativeZero));
}
