c# - what does NaN mean for doubles?

Question

What's the difference between NaN and Infinity? When does NaN appear? What is it?

Answer 1

From Wikipedia :

In computing, NaN (Not a Number) is a value of the numeric data type representing an undefined or unrepresentable value, especially in floating-point calculations. Systematic use of NaNs was introduced by the IEEE 754 floating-point standard in 1985, along with the representation of other non-finite quantities like infinities.

And from MSDN :

• Represents a value that is not a number (NaN). This field is constant.

• The value of this constant is the result of dividing zero by zero.

• This constant is returned when the result of an operation is undefined.

• Use IsNaN to determine whether a value is not a number. It is not possible to determine whether a value is not a number by comparing it to another value equal to NaN.

Where as Infinity (positive infinity and negative infinity) is the result of a floating point operation that causes an overflow (For example 3.0 / 0).