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Math.IEEERemainder Method

Visual Studio 2010

Returns the remainder resulting from the division of a specified number by another specified number.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

C#
C++
F#
VB
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'Declaration
Public Shared Function IEEERemainder ( _
	x As Double, _
	y As Double _
) As Double

Parameters

x
Type: System.Double
A dividend.
y
Type: System.Double
A divisor.

Return Value

Type: System.Double
A number equal to x - (y Q), where Q is the quotient of x / y rounded to the nearest integer (if x / y falls halfway between two integers, the even integer is returned).
If x - (y Q) is zero, the value +0 is returned if x is positive, or -0 if x is negative.
If y = 0, NaN is returned.

This operation complies with the remainder operation defined in Section 5.1 of ANSI/IEEE Std 754-1985; IEEE Standard for Binary Floating-Point Arithmetic; Institute of Electrical and Electronics Engineers, Inc; 1985.

The IEEERemainder method is not the same as the modulus operator. Although both return the remainder after division, the formulas they use are different. The formula for the IEEERemainder method is:

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IEEERemainder = dividend - (divisor * Math.Round(dividend / divisor))

In contrast, the formula for the modulus operator is:

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Modulus = (Math.Abs(dividend) - (Math.Abs(divisor) * 
          (Math.Floor(Math.Abs(dividend) / Math.Abs(divisor))))) * 
          Math.Sign(dividend)

The following example contrasts the remainder returned by the IEEERemainder method with the remainder returned by the modulus division operator.

C#
VB
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Module Example
   Public Sub Main()
      Console.WriteLine("{0,35} {1,20}", "IEEERemainder", "Modulus")
      ShowRemainders(3, 2)
      ShowRemainders(4, 2)
      ShowRemainders(10, 3)
      ShowRemainders(11, 3)
      ShowRemainders(27, 4)
      ShowRemainders(28, 5)
      ShowRemainders(17.8, 4)
      ShowRemainders(17.8, 4.1)
      ShowRemainders(-16.3, 4.1)
      ShowRemainders(17.8, -4.1)
      ShowRemainders(-17.8, -4.1)
   End Sub

   Private Sub ShowRemainders(number1 As Double, number2 As Double)
      Dim formula As String = String.Format("{0} / {1} = ", number1, number2)
      Console.WriteLine("{0,-16} {1,18} {2,20}", _
                       formula, _
                       Math.IEEERemainder(number1, number2), _
                       number1 Mod number2)  
   End Sub
End Module
' The example displays the following output:
'       
'                             IEEERemainder              Modulus
'       3 / 2 =                          -1                    1
'       4 / 2 =                           0                    0
'       10 / 3 =                          1                    1
'       11 / 3 =                         -1                    2
'       27 / 4 =                         -1                    3
'       28 / 5 =                         -2                    3
'       17.8 / 4 =                      1.8                  1.8
'       17.8 / 4.1 =                    1.4                  1.4
'       -16.3 / 4.1 =    0.0999999999999979                   -4
'       17.8 / -4.1 =                   1.4                  1.4
'       -17.8 / -4.1 =                 -1.4                 -1.4

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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