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Math.IEEERemainder Method (Double, Double)

 

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

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

public static double IEEERemainder(
	double x,
	double y
)

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.

TheIEEERemainder 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:

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

In contrast, the formula for the modulus operator is:

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.

using System;

public class Example
{
   public static void 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);
   }

   private static void ShowRemainders(double number1, double number2)
   {
      string formula = String.Format("{0} / {1} = ", number1, number2);
      Console.WriteLine("{0,-16} {1,18} {2,20}", 
                       formula, 
                       Math.IEEERemainder(number1, number2), 
                       number1 % number2);  
   }
}
// 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

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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