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Missing class template error

Lacy9265 (119)
For this code I have to use an adjacency matrix to represent the graph. I'm having trouble in my driver.cpp file calling on the graph.h file because it says class template is missing. I have included my Driver.h file and Graph.h file. The error happens on L18.

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  #include "Graph.h"
#include <iostream>
#include <string>
#include <stdio.h>
#include <conio.h>

using namespace std;

int main()
{
   
    int NodeNum, MaxiEdge, Start, End;

    cout << "Enter vertices count: ";

    cin >> NodeNum;

    Graph graph(NodeNum); // argument list missing class template 

    MaxiEdge = NodeNum * (NodeNum - 1);

    for (int it = 0; it < MaxiEdge; it++)
    {
        cout << "Enter -1 -1 to exit";

        cin >> Start >> End;

        if ((Start == -1) && (End == -1))
            break;

        graph.add(Start, End);
    }

    graph.display();

    system("pause");

    return 0;
}

#ifndef _GRAPH
#define _GRAPH

#include "GraphInterface.h"
#include <string>
#include <fstream>
#include <iostream>

using namespace std;

template<class LabelType>
class Graph : public GraphInterface<LabelType>
{
private:
    LabelType nVal;
    LabelType** adj;
    bool* visitedEdge;
    int edgeWeight;
    int numOfEdges;
    int numOfVertices;


public:
    Graph(LabelType n);
    int getNumVertices() const;
    int getNumEdges() const;
    void add(LabelType start, LabelType end);

    bool remove(LabelType start, LabelType end);

    int getEdgeWeight(LabelType start, LabelType end) const;


    void display();
}; 
template<class LabelType>
Graph<LabelType>::Graph(LabelType nVal)
{
    this->nVal = nVal;

    visitedEdge = new bool[nVal];

    adj = new int* [nVal];

    for (int it = 0; it < nVal; it++)
    {
        adj[it] = new int[nVal];

        for (int jth = 0; jth < nVal; jth++)
        {
            adj[it][jth] = 0;
        }
    }

}


template<class LabelType>
void Graph<LabelType>::add(LabelType start, LabelType end)
{
    if (start > nVal || end > nVal || start < 0 || end < 0)
    {
        cout << "Invalid edge!\nVal";
    }

    else
    {
        adj[start - 1][end - 1] = 1;
    }
}


template<class LabelType>
int Graph<LabelType>::getNumVertices() const
{
    return numOfVertices;
}

template<class LabelType>
int Graph<LabelType>::getNumEdges() const
{
    return numOfEdges;
}

template<class LabelType>
int Graph<LabelType>::getEdgeWeight(LabelType start, LabelType end) const
{
    return numOfVertices;
}

template<class LabelType>
bool Graph<LabelType>::remove(LabelType start, LabelType end)
{
    bool result = false;

    if (start > nVal || end > nVal || start < 0 || end < 0)
    {
        cout << "Invalid edge!\nVal";
    }

    else
    {
        adj[start - 1][end - 1] = -1;
    }
    return result;
}

#endif
Last edited on
coder777 (8439)
You need to provide the <LabelType>:

Graph<int> graph(NodeNum); // argument list missing class template
helios (17506)
Since NodeNum is an int and you're passing it to the constructor of a Graph<LabelType>, and the only Graph<LabelType> constructor takes a single parameter of type LabelType, that would mean that graph should be of type Graph<int>:
 
 
Graph<int> graph(NodeNum);

The compiler is unable to make the reasoning I made above (in this case, anyway). You need to tell it which template you're instantiating.
Lacy9265 (119)
When I do 

1
2
 
 
Graph<int> graph(NodeNum)


it gives me this error now

Error C2259 'Graph<int>': cannot instantiate abstract class
coder777 (8439)
Not the code you provided. The error is:
/tmp/ccC0dY1v.o: In function `main':
:(.text.startup+0x182): undefined reference to `Graph<int>::display()'
because display() is not implemented.

[EDIT]
There might something in GraphInterface you didn't provide.
Last edited on
Lacy9265 (119)
Here is my code for the updated Graph.h and GraphInterface.h file. Also, I have deleted display from the code.
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#ifndef _GRAPH_INTERFACE
#define _GRAPH_INTERFACE

 template < class LabelType>
class GraphInterface
 {
 public:

/** Gets the number of vertices in this graph.
@pre   None.
 @return  The number of vertices in the graph. */
virtual int getNumVertices() const = 0;
		
 /** Gets the number of edges in this graph.
  @pre   None.
  @return  The number of edges in the graph. */
 virtual int getNumEdges() const = 0;


   /** Creates an undirected edge in this graph between two vertices
   that have the given labels. If such vertices do not exist, creates
   them and adds them to the graph before creating the edge.
   @param start  A label for the first vertex.
   @param end  A label for the second vertex.
   @param edgeWeight  The integer weight of the edge.
  @return  True if the edge is created, or false otherwise. */
  virtual bool add(LabelType start, LabelType end, int edgeWeight) = 0;


  /** Removes an edge from this graph. If a vertex has no other edges,
  it is removed from the graph since this is a connected graph.
  @pre  None.
 @param start  A label for the first vertex.
  @param end  A label for the second vertex.
 @return  True if the edge is removed, or false otherwise. */
 virtual bool remove(LabelType start, LabelType end) = 0;


  /** Gets the weight of an edge in this graph.
   @return  The weight of the specified edge.
 If no such edge exists, returns a negative integer. */
	 virtual int getEdgeWeight(LabelType start, LabelType end) const = 0;
	

  /** Performs a depth-first search of this graph beginning at the given
vertex and calls a given function once for each vertex visited.
 @param start  A label for the first vertex.
 @param visit  A client-defined function that performs an operation on
  or with each visited vertex. */
	virtual void depthFirstTraversal(LabelType start, void visit(LabelType&)) = 0;


 /** Performs a breadth-first search of this graph beginning at the given
  vertex and calls a given function once for each vertex visited.
  @param start  A label for the first vertex.
 @param visit  A client-defined function that performs an operation on
   or with each visited vertex. */
 virtual void breadthFirstTraversal(LabelType start, void visit(LabelType&)) = 0;


 /** Destroy this graph and frees assigned memory*/
 virtual ~GraphInterface(){ }
 }; // end GraphInterface
#endif

#ifndef _GRAPH
#define _GRAPH

#include "GraphInterface.h"
#include <string>
#include <fstream>
#include <iostream>


template<class LabelType>
class Graph : public GraphInterface<LabelType>
{
private:
    LabelType nVal;
    LabelType** adj;
    bool* visitedEdge;
    int edgeWeight;
    int numOfEdges;
    int numOfVertices;


public:
    Graph(LabelType n);
    int getNumVertices() const;
    int getNumEdges() const;
    void add(LabelType start, LabelType end);

    bool remove(LabelType start, LabelType end);

    int getEdgeWeight(LabelType start, LabelType end) const;
    void breadthFirstTraversal(LabelType start, void visit(LabelType&));
    void depthFirstTraversal(LabelType start, void visit(LabelType&));

    void display();
};
template<class LabelType>
Graph<LabelType>::Graph(LabelType nVal)
{
    this->nVal = nVal;

    visitedEdge = new bool[nVal];

    adj = new int* [nVal];

    for (int it = 0; it < nVal; it++)
    {
        adj[it] = new int[nVal];

        for (int jth = 0; jth < nVal; jth++)
        {
            adj[it][jth] = 0;
        }
    }

}


template<class LabelType>
void Graph<LabelType>::add(LabelType start, LabelType end)
{
    if (start > nVal || end > nVal || start < 0 || end < 0)
    {
        std::cout << "Invalid edge!\nVal";
    }

    else
    {
        adj[start - 1][end - 1] = 1;
    }
}


template<class LabelType>
int Graph<LabelType>::getNumVertices() const
{
    return numOfVertices;
}

template<class LabelType>
int Graph<LabelType>::getNumEdges() const
{
    return numOfEdges;
}

template<class LabelType>
int Graph<LabelType>::getEdgeWeight(LabelType start, LabelType end) const
{
    return numOfVertices;
}

template<class LabelType>
bool Graph<LabelType>::remove(LabelType start, LabelType end)
{
    bool result = false;

    if (start > nVal || end > nVal || start < 0 || end < 0)
    {
        std::cout << "Invalid edge!\nVal";
    }

    else
    {
        adj[start - 1][end - 1] = -1;
    }
    return result;
}

template<class LabelType>
void depthFirstTraversal(LabelType start, void visit(LabelType&)) {
    
}

template<class LabelType>
void breadthFirstTraversal(LabelType start, void visit(LabelType&)) {

}

#endif
Lacy9265 (119)
Never mind figured it out.
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