Although we can read in LR:

NaN (i.e. "Not a Number"): occurs if you attempted to perform an illegal mathematical operation, like getting the square root of a negative number. Any further calculation made with a NaN will lead to a NaN value. Str or Format methods return a string beginning with "NaN", e.g. "NaN(021)".

This is no true. There is an error, since if I write this code:

msgbox str(Sqrt(-5))

I get

-1.#IND

This error is not very important unless you pretend to detect NaN numbers in your program. Both Nan and Infinity use "#" when converting to string.

I've created a function like this:

Function IsNotANumber (x as double) as Boolean if Str(x).InStr("#") = 0 Then Return False else Return True end function

This works very well. But, can I trust Xojo will keep this conversion to string for ever?

Have you created your own function for this? How do you do it?

Should I use "IsNumeric"?

Thanks in advance,