Question

I’m trying to include a set, inside a struct, but I don’t know how to pass the callback compare function to the set constructor when doing this.

This is a basic example of what I’ve tried:

struct pointT { 
    int x; 
    int y; 
};

struct pathT{
    Stack<pointT> pointsInPath;
    Set<pointT> pointsIncluded; // need callback here?
};

// Tried this.
//struct pathT{
    //Stack<pointT> pointsInPath;
    //Set<pointT> pointsIncluded(ComparePoints); //doesn't work of course
//};


//Callback function to compare set of points.
int ComparePoints(pointT firstPoint, pointT secondPoint){

    if (firstPoint.x == secondPoint.x && firstPoint.y == secondPoint.y) return 0;
    if (firstPoint.x < secondPoint.x) return -1;
    else return 1;
}


int main() {

    Set<pointT> setOfPoints(ComparePoints); // this works fine
    //pathT allPaths; // not sure how to assign call back function here to a set inside a struct

    return 0;
}

Answer 1

Your struct in c++ is automatically a class.

therefore you can provide a constructor

struct pathT {
    public:
    pathT();

    private:
    Stack<pointT> pointsInPath;
    Set<pointT> pointsIncluded; 
};

pathT::pathT()
: pointsIncluded(ComparePoints)
{

}

regards