Question

My problem is following, I have a function which takes one function as a parameter. The problem is that in some cases the passed function fEval() needs to be called with two parameters instead of one as fEval(somevalue1,somevalue2)

Func(double (*fEval)(double F1),double min, double max,...)
{
    double value1 = fEval(10);

    // do something here

    double value2 = fEval(20,30);
}

So what would be the correct way to implement Func function ?
I know I can’t do it either

Func(double (*fEval)(double F1),double min, double max,...)

or

Func(double (*fEval)(double F1,double F2),double min, double max,...)

Thanks !

Okay let me rephrase the problem. I need to create a function which could take a one unknown function as a first parameter, two different values and an argument list.
Something like

double Function(RandomFunction, val1, val2, ...);

The random function will be either:

double Func1(double x)
{
    m_x = x;
    //Calling function
    // Set other things
}
double Func2(double x,double y)
{
    m_y = y;
    m_x = x;
    //Calling function
    // Set other things
}

I’ll try that functor way but I’m not sure is it right way to do this ? Doesn’t it require me to overload () inside of the possible functions what could be called ?

Answer 1

You probably should require a functor that has operator() overloaded to take one or two arguments:

struct Functor {
    double operator()(double d) {
        ....
    }

    double operator()(double d1, double d2) {
        .... 
    }
};

void Func(Functor f, double min, double max, ...) {
    double value1 = f(10);

    // do something here

    double value2 = f(20, 30);
}

Other than that (besides passing around variadic functions, which wouldn’t be good because it couldn’t know whether it was being called with one or two arguments) I don’t think there is another good way to have a function that can take both 1 or 2 arguments.

And as ildjarn mentioned in the comments, you could also make it a template so it can take any kind of functor:

template<typename Functor_t>
void Func(Functor_t f, double min, double max, ...) {
    // same as above
}