[C++] Check for whole numbers

Hi. I learnt basic C++ programming last year, and have not been using it since. I wrote a program to do some calculations, and I'm wondering if there is any way to check for whole numbers?

For example, if ( a == whole number ), perform a function, else, quit the program.

If there isn't a way to check for whole numbers, I'd have to manually read the results and then perform the functions on the results (of which are whole numbers) itself, which is mighty tedious.

Thanks in advance!

Since there is the possibility of coming up with non-whole numbers, I assume you are using floats or doubles. In that case, try casting the number to an int and see if the result is reasonably close. (I say reasonably close because floats are prone to round-off errors, i.e. you would probably consider 5.999999999999999999999 and 6.000000000000001 whole numbers, even though when rounded to ints they would compare inequal with the == operator. It will take some experimentation to see what you should define "reasonably close" as for this project.)
With that in mind, a function: