Pass a function reference to a struct inside that function

Question

Have some tricky code and am stuck on a piece.

I have a function that is descended from a virtual base class.

Inside that function is a functor. The functor needs to be able to access all the objects inside of this function and its parent class. But, when passing a reference to "this" or to the function name, I get an error.

The reason for all this complication is to speed up the code. The algorithm I'm coding really only has one expensive part. My intent is to parallelize that part. However, that step accumulates over two values simultaneously, through several steps. So, I need to override some operators. A functor seemed like the easiest way to implement this.

Can anyone suggest how to solve this.

representative code below:

myClassA Glm{
public:
    virtual int functionA(int a, int b)=0;
}

class myClassB : public myClassA {
    public:
    virtual int functionA(int a, int b);
}

int functionA(int a, int b){


    // do some stuff

    struct MyFunctor : public binary_function<Fraction, DoubleIterator, Fraction> {

        MyFunctor(myClassA& in_class, int A) : myClassA(in_class), column(iColumn) {

        }                
        myClassA& myClassA;
        int A;

        Fraction operator()(double B, int A, ) {

            double C = doFancyStuff(A,B);
            return C;
        }

    }

    //use stl to accumulate
    accumulate(data.begin(), data.end(), temp, MyFunctor(*this,  column) );

}

Answer 1

The main problem here is premature optimization.

Technically, replace the current …

int functionA(int a, int b){

with …

int myClassB::functionA(int a, int b){

and at least your problems with this should be gone.

Then, not that placing a reference as a data member, like your …

myClassA& myClassA;

makes instances non-assignable. And a functor object “should” be assignable. So if you decide to go on with this, perhaps better replace that with …

myClassA* pMyClassA_;

and change the initialization accordingly.

Cheers & hth.,