It's very difficult to ascertain what you're trying to do. You said in the OP
yet the name of your class is gcd, which suggests you want to find the greatest common divisor.
What are you trying to do? If you want to check that a double is actually an integer, you can use the floor() function to find the largest integer that is less than or equal to your number. IOW, val - floor(val) should evaluate to 0.0 if val is an integer.
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