How Can I Reliably Identify NaN Values in C ?

Identifying NaN Values in C

In C , the presence of NaN (Not-a-Number) values can arise while performing floating-point operations. Detecting these special values is crucial for ensuring program correctness.

Isn't there an isnan() function?

You might be wondering about the existence of an isnan() function. In MinGW, the header file does not provide an isnan() function. Instead, you should include to access this functionality.

A Unique Property of NaNs

The IEEE floating-point standard specifies an intriguing property for NaN values: any comparison involving a NaN will always evaluate to false. This means that if you compare a floating-point variable f with itself (f != f) and the result is true, it unequivocally indicates that f is NaN.

Compiler Considerations

While this trick should theoretically work for compilers that adhere to IEEE floating-point standards, it's important to verify its effectiveness with your specific compiler. Some compilers may optimize code in ways that undermine this approach.

In cases where reliability is paramount, it's recommended to consult your compiler's documentation or perform empirical testing to confirm the behavior of NaN comparisons.

The above is the detailed content of How Can I Reliably Identify NaN Values in C ?. For more information, please follow other related articles on the PHP Chinese website!