Edit: Passing the operator as a reference doesnt work. For simplicity, understand it as a function pointer. You just send the pointer, not a reference. I think you are trying to write something like this.
struct Square
{
double operator()(double number) { return number * number; }
};
template <class Function>
double integrate(Function f, double a, double b, unsigned int intervals)
{
double delta = (b - a) / intervals, sum = 0.0;
while(a < b)
{
sum += f(a) * delta;
a += delta;
}
return sum;
}
. .
std::cout << "interval : " << i << tab << tab << "intgeration = "
<< integrate(Square(), 0.0, 1.0, 10) << std::endl;