Check double variable if it contains an integer, and not floating point

Question

What I mean is the following:

  double d1 =555;   double d2=55.343 

I want to be able to tell that d1 is an integer while d2 is not. Is there an easy way to do it in c/c++?

Answer 1

Use std::modf:

double intpart; modf(value, &intpart) == 0.0 

Don't convert to int! The number 1.0e+300 is an integer too you know.

Edit: As Pete Kirkham points out, passing 0 as the second argument is not guaranteed by the standard to work, requiring the use of a dummy variable and, unfortunately, making the code a lot less elegant.