Using floating point numbers, 0.0 / 0.0 isn’t a “divide by zero” error; it results in NaN. This C program prints -nan: #include <stdio.h> int main() { float x = 0.0 / 0.0; printf(“%f\n”, x); return 0; } In terms what NaN looks like to the computer, two “invalid” numbers are reserved for “signaling” and … Read more
To add to Vladimir F’s answer I’ll mention that gfortran 5.0 (but not earlier) supports the IEEE intrinsic modules. Instead of real x x=0 x=0/x one can use use, intrinsic :: iso_fortran_env use, intrinsic :: ieee_arithmetic integer(int32) i real(real32) x x = ieee_value(x, ieee_quiet_nan) i = transfer(x,i) This gives you a little flexibility over which … Read more
Python does not have a built-in name nan, nor is there a keyword. It looks as if you forgot to import it; numpy defines such a name: from numpy import nan From the local name df I infer you are probably using pandas; pandas’ documentation usually uses np.nan, where np is the numpy module imported … Read more
It was thought to be a good idea when IEEE754 and NaN’s were developed. I have actually seen it used to store the reason why a NaN was created. Today, I wouldn’t use it in portable code for several reasons. How sure are you that this payload will survive for example an assignment? If you … Read more
I found an article addressing your question: .NET Security Blog: Why == and the Equals Method Return Different Results for Floating Point Values According to IEC 60559:1989, two floating point numbers with values of NaN are never equal. However, according to the specification for the System.Object::Equals method, it’s desirable to override this method to provide … Read more
NaN‘s are unusual: they are not equal to anything, even themselves. You need to use isNaN(inbperr) to tell whether a value is a NaN or not.
If you do any of the following without horsing around with the floating-point environment, you should get a NaN where you didn’t have one before: 0/0 (either sign on top and bottom) inf/inf (either sign on top and bottom) inf – inf or (-inf) + inf or inf + (-inf) or (-inf) – (-inf) 0 … Read more
One of the properties of NAN is that NAN != NAN, unlike all other numbers. However, the implementation of set first checks to see if id(x) matches the existing member at a hash index before it tries to insert a new one. If you have two objects with different ids that both have the value … Read more
You are right about the JSON spec: Numeric values that cannot be represented as sequences of digits (such as Infinity and NaN) are not permitted. The solution must also come from the spec, since a custom “JSON” encoder would not produce valid JSON anyway (you would have to write a custom decoder as well, and … Read more