Question

I believe this question has been asked before. I tried looking for it but still can’t figure out the problem. I’d greatly appreciate any help I can get here. Thanks

I get the following error. I get an idea that I am not initializing the Vertex once I call the constructor of the Edge. But I can’t seem to figure out how.

10369.cpp: In constructor ‘Edge::Edge(Vertex, Vertex)’:
10369.cpp:34: error: no matching function for call to ‘Vertex::Vertex()’
10369.cpp:30: note: candidates are: Vertex::Vertex(int, int)
10369.cpp:6: note:                 Vertex::Vertex(const Vertex&)
10369.cpp:34: error: no matching function for call to ‘Vertex::Vertex()’
10369.cpp:30: note: candidates are: Vertex::Vertex(int, int)
10369.cpp:6: note:                 Vertex::Vertex(const Vertex&)

    #include <iostream>
    #include <math.h>
    using namespace std;

//Vertex in a graph, with x & y coordinates 
    class Vertex{
        int x , y;
        public:
            Vertex(int, int);
            ~Vertex();

            int GetX() {return x;};
            int GetY() {return y;};

    }; 

// Edge of a graph calculated from two vertices
    class Edge{
        Vertex U , V;
        float edge_weight;
            public:
                Edge(Vertex , Vertex);
                ~Edge();

                 float GetEdgeWeight() { return edge_weight; }


    };

    Vertex::Vertex(int _x , int _y){
        x = _x;
        y = _y;
    } 

// The edge weight is calculated using the pythagoras
    Edge::Edge(Vertex _U , Vertex _V){
        U = _U;
        V = _V; 
        int x = V.GetY() - U.GetY();
        int y = V.GetX() - U.GetX();
        edge_weight = sqrt(pow(x,2) + pow(y,2));

    }   
    int main (int argc , char *argv[]){

        Vertex V1(0,1) ; 
        Vertex V2(0,3);
        Edge E(V1, V2);
        float x = E.GetEdgeWeight();
        cout << x << endl;


        return 0;
    }

Answer 1

Always use constructor initialiser lists to initialise data members — your Vertex has no default constructor, this is one of the cases where you absolutely must use an init list.

Edge::Edge(Vertex U, Vertex V) : U(U), V(V), edge_weight(...) { }
Vertex::Vertex(int x, int y) : x(x), y(y) { }