Checking if a double (or float) is NaN in C++

Question

Is there an isnan() function?

PS.: I\'m in MinGW (if that makes a difference).

I had this solved by using isnan() from , which doe

Answer 1

The following code uses the definition of NAN (all exponent bits set, at least one fractional bit set) and assumes that sizeof(int) = sizeof(float) = 4. You can look up NAN in Wikipedia for the details.

bool IsNan( float value ) { return ((*(UINT*)&value) & 0x7fffffff) > 0x7f800000; }