c++ - What is the most effective way for float and double comparison?

What would be the most efficient way to compare two
double or two float
values?

Simply doing this is not
correct:

bool CompareDoubles1
            (double A, double B)
{
 return A ==
            B;
}

But
something like:

bool
            CompareDoubles2 (double A, double B) 
{
 diff = A - B;

            return (diff < EPSILON) && (-diff <
            EPSILON);
}

Seems
to waste processing.

Does anyone know a smarter
float comparer?