C# Float and Double Special Values

Description

Floating-point types have values that certain operations treat specially. These special values are

• NaN (Not a Number)
• PositiveInfinity
• NegativeInfinity
• -0

The float and double classes have constants for NaN, PositiveInfinity, and NegativeInfinity, as well as other values.

For example:

Console.WriteLine (double.NegativeInfinity);   // -Infinity 

The constants that represent special values for double and float are as follows:

Example

Dividing a nonzero number by zero results in an infinite value. For example:

Console.WriteLine ( 1.0 /  0.0);                  //  Infinity 
Console.WriteLine (-1.0 /  0.0);                  // -Infinity 
Console.WriteLine ( 1.0 / -0.0);                  // -Infinity 
Console.WriteLine (-1.0 / -0.0);                  //  Infinity 
/* ww w.j av  a 2  s.  co m*/

Dividing zero by zero, or subtracting infinity from infinity, results in a NaN. For example:

Console.WriteLine ( 0.0 /  0.0);                  //  NaN 
Console.WriteLine ((1.0 /  0.0) - (1.0 / 0.0));   //  NaN 

Equality

When using ==, a NaN value is never equal to another value, even another NaN value:

Console.WriteLine (0.0 / 0.0 == double.NaN);    // False 

To test whether a value is NaN, you must use the float.IsNaN or double.IsNaN method:

Console.WriteLine (double.IsNaN (0.0 / 0.0));   // True 

When using object.Equals, however, two NaN values are equal:

Console.WriteLine (object.Equals (0.0 / 0.0, double.NaN));   // True