c++ inheritance error

baronobeefdip · 04-29-2014, 02:56 PM

I am having an error with my program where whenever I compile it, the compiler claims that the variables that I am trying to use inside of some of the functions are not being declared in the scope. I setup the inheritance from what I was able to see in a large amount of the things I have seen in the various google searches I have performed. These are my header files. You might need to copy these into your own IDE and compile them yourself in order to find out what is happening here.
linkedList.h

Code:

#ifndef H_UnorderedLinkedList
#define H_UnorderedLinkedList

#include "linkedList.h"

using namespace std;

template <class Type>
class unorderedLinkedList: public linkedListType<Type>
{
public:
    bool search(const Type& searchItem) const;
      //Function to determine whether searchItem is in the list.
      //Postcondition: Returns true if searchItem is in the list,
      //    otherwise the value false is returned.

    void insertFirst(const Type& newItem);
      //Function to insert newItem at the beginning of the list.
      //Postcondition: first points to the new list, newItem is
      //    inserted at the beginning of the list, last points to
      //    the last node, and count is incremented by 1.
      //               

    void insertLast(const Type& newItem);
      //Function to insert newItem at the end of the list.
      //Postcondition: first points to the new list, newItem is
      //    inserted at the end of the list, last points to the
      //    last node, and count is incremented by 1.

    void deleteNode(const Type& deleteItem);
      //Function to delete deleteItem from the list.
      //Postcondition: If found, the node containing deleteItem
      //    is deleted from the list. first points to the first 
      //    node, last points to the last node of the updated 
      //    list, and count is decremented by 1.
};


template <class Type>
bool unorderedLinkedList<Type>::
                   search(const Type& searchItem) const
{
    nodeType<Type> *current; //pointer to traverse the list
    bool found = false;
    
    current = first; //set current to point to the first 
                     //node in the list

    while (current != NULL && !found)    //search the list
        if (current->info == searchItem) //searchItem is found
            found = true;
        else
            current = current->link; //make current point to
                                     //the next node
    return found; 
}//end search

template <class Type>
void unorderedLinkedList<Type>::insertFirst(const Type& newItem)
{
    nodeType<Type> *newNode; //pointer to create the new node

    newNode = new nodeType<Type>; //create the new node

    newNode->info = newItem;    //store the new item in the node
    newNode->link = first;      //insert newNode before first
    first = newNode;            //make first point to the
                                //actual first node
    count++;                    //increment count

    if (last == NULL)   //if the list was empty, newNode is also 
                        //the last node in the list
        last = newNode;
}//end insertFirst

template <class Type>
void unorderedLinkedList<Type>::insertLast(const Type& newItem)
{
    nodeType<Type> *newNode; //pointer to create the new node

    newNode = new nodeType<Type>; //create the new node

    newNode->info = newItem;  //store the new item in the node
    newNode->link = NULL;     //set the link field of newNode
                              //to NULL

    if (first == NULL)  //if the list is empty, newNode is 
                        //both the first and last node
    {
        first = newNode;
        last = newNode;
        count++;        //increment count
    }
    else    //the list is not empty, insert newNode after last
    {
        last->link = newNode; //insert newNode after last
        last = newNode; //make last point to the actual 
                        //last node in the list
        count++;        //increment count
    }
}//end insertLast


template <class Type>
void unorderedLinkedList<Type>::deleteNode(const Type& deleteItem)
{
    nodeType<Type> *current; //pointer to traverse the list
    nodeType<Type> *trailCurrent; //pointer just before current
    bool found;

    if (first == NULL)    //Case 1; the list is empty. 
        cout << "Cannot delete from an empty list."
             << endl;
    else
    {
        if (first->info == deleteItem) //Case 2 
        {
            current = first;
            first = first->link;
            count--;
            if (first == NULL)    //the list has only one node
                last = NULL;
            delete current;
        }
        else //search the list for the node with the given info
        {
            found = false;
            trailCurrent = first;  //set trailCurrent to point
                                   //to the first node
            current = first->link; //set current to point to 
                                   //the second node

            while (current != NULL && !found)
            {
                if (current->info != deleteItem) 
                {
                    trailCurrent = current;
                    current = current-> link;
                }
                else
                    found = true;
            }//end while

            if (found) //Case 3; if found, delete the node
            {
                trailCurrent->link = current->link;
                count--;

                if (last == current)   //node to be deleted 
                                       //was the last node
                    last = trailCurrent; //update the value 
                                         //of last
                delete current;  //delete the node from the list
            }
            else
                cout << "The item to be deleted is not in "
                     << "the list." << endl;
        }//end else
    }//end else
}//end deleteNode


#endif

unorderedLinkedList.h

Code:

#ifndef H_UnorderedLinkedList
#define H_UnorderedLinkedList

#include "linkedList.h"

using namespace std;

template <class Type>
class unorderedLinkedList: public linkedListType<Type>
{
public:
    bool search(const Type& searchItem) const;
      //Function to determine whether searchItem is in the list.
      //Postcondition: Returns true if searchItem is in the list,
      //    otherwise the value false is returned.

    void insertFirst(const Type& newItem);
      //Function to insert newItem at the beginning of the list.
      //Postcondition: first points to the new list, newItem is
      //    inserted at the beginning of the list, last points to
      //    the last node, and count is incremented by 1.
      //               

    void insertLast(const Type& newItem);
      //Function to insert newItem at the end of the list.
      //Postcondition: first points to the new list, newItem is
      //    inserted at the end of the list, last points to the
      //    last node, and count is incremented by 1.

    void deleteNode(const Type& deleteItem);
      //Function to delete deleteItem from the list.
      //Postcondition: If found, the node containing deleteItem
      //    is deleted from the list. first points to the first 
      //    node, last points to the last node of the updated 
      //    list, and count is decremented by 1.
};


template <class Type>
bool unorderedLinkedList<Type>::
                   search(const Type& searchItem) const
{
    nodeType<Type> *current; //pointer to traverse the list
    bool found = false;
    
    current = *first; //set current to point to the first 
                     //node in the list

    while (current != NULL && !found)    //search the list
        if (current->info == searchItem) //searchItem is found
            found = true;
        else
            current = current->link; //make current point to
                                     //the next node
    return found; 
}//end search

template <class Type>
void unorderedLinkedList<Type>::insertFirst(const Type& newItem)
{
    nodeType<Type> *newNode; //pointer to create the new node

    newNode = new nodeType<Type>; //create the new node

    newNode->info = newItem;    //store the new item in the node
    newNode->link = first;      //insert newNode before first
    first = newNode;            //make first point to the
                                //actual first node
    count++;                    //increment count

    if (last == NULL)   //if the list was empty, newNode is also 
                        //the last node in the list
        last = newNode;
}//end insertFirst

template <class Type>
void unorderedLinkedList<Type>::insertLast(const Type& newItem)
{
    nodeType<Type> *newNode; //pointer to create the new node

    newNode = new nodeType<Type>; //create the new node

    newNode->info = newItem;  //store the new item in the node
    newNode->link = NULL;     //set the link field of newNode
                              //to NULL

    if (first == NULL)  //if the list is empty, newNode is 
                        //both the first and last node
    {
        first = newNode;
        last = newNode;
        count++;        //increment count
    }
    else    //the list is not empty, insert newNode after last
    {
        last->link = newNode; //insert newNode after last
        last = newNode; //make last point to the actual 
                        //last node in the list
        count++;        //increment count
    }
}//end insertLast


template <class Type>
void unorderedLinkedList<Type>::deleteNode(const Type& deleteItem)
{
    nodeType<Type> *current; //pointer to traverse the list
    nodeType<Type> *trailCurrent; //pointer just before current
    bool found;

    if (first == NULL)    //Case 1; the list is empty. 
        cout << "Cannot delete from an empty list."
             << endl;
    else
    {
        if (first->info == deleteItem) //Case 2 
        {
            current = first;
            first = first->link;
            count--;
            if (first == NULL)    //the list has only one node
                last = NULL;
            delete current;
        }
        else //search the list for the node with the given info
        {
            found = false;
            trailCurrent = first;  //set trailCurrent to point
                                   //to the first node
            current = first->link; //set current to point to 
                                   //the second node

            while (current != NULL && !found)
            {
                if (current->info != deleteItem) 
                {
                    trailCurrent = current;
                    current = current-> link;
                }
                else
                    found = true;
            }//end while

            if (found) //Case 3; if found, delete the node
            {
                trailCurrent->link = current->link;
                count--;

                if (last == current)   //node to be deleted 
                                       //was the last node
                    last = trailCurrent; //update the value 
                                         //of last
                delete current;  //delete the node from the list
            }
            else
                cout << "The item to be deleted is not in "
                     << "the list." << endl;
        }//end else
    }//end else
}//end deleteNode


#endif

and here is the error I keep getting

Code:

g++ ajllab10.cpp -o lab10
In file included from graphType.h:16:0,
                 from ajllab10.cpp:1:
unorderedLinkedList.h: In member function ‘bool unorderedLinkedList<Type>::search(const Type&) const’:
unorderedLinkedList.h:54:16: error: ‘first’ was not declared in this scope
unorderedLinkedList.h: In member function ‘void unorderedLinkedList<Type>::insertFirst(const Type&)’:
unorderedLinkedList.h:74:22: error: ‘first’ was not declared in this scope
unorderedLinkedList.h:77:5: error: ‘count’ was not declared in this scope
unorderedLinkedList.h:79:9: error: ‘last’ was not declared in this scope
unorderedLinkedList.h: In member function ‘void unorderedLinkedList<Type>::insertLast(const Type&)’:
unorderedLinkedList.h:95:10: error: ‘first’ was not declared in this scope
unorderedLinkedList.h:99:9: error: ‘last’ was not declared in this scope
unorderedLinkedList.h:100:9: error: ‘count’ was not declared in this scope
unorderedLinkedList.h:104:9: error: ‘last’ was not declared in this scope
unorderedLinkedList.h:107:9: error: ‘count’ was not declared in this scope
unorderedLinkedList.h: In member function ‘void unorderedLinkedList<Type>::deleteNode(const Type&)’:
unorderedLinkedList.h:119:10: error: ‘first’ was not declared in this scope
unorderedLinkedList.h:128:13: error: ‘count’ was not declared in this scope
unorderedLinkedList.h:130:17: error: ‘last’ was not declared in this scope
unorderedLinkedList.h:155:17: error: ‘count’ was not declared in this scope
unorderedLinkedList.h:157:21: error: ‘last’ was not declared in this scope
make: *** [lab10] Error 1

What is going to make this error go away, I can't see why it is complaining about this error since all of the inheritance and other things have been declared and such, I can't seem to find out what exactly is happening here. I hope I can get some help with this quickly. Thanks for your time.

ntubski · 04-29-2014, 04:42 PM

You posted the contents of unorderedLinkedList.h twice? The .cpp file may also be relevant.

baronobeefdip · 04-29-2014, 04:56 PM

sorry, The file I copied incorrectly was
linkedList.h

Code:

#ifndef H_LinkedListType
#define H_LinkedListType

#include <iostream>
#include <cassert>

using namespace std;

//Definition of the node

template <class Type>
struct nodeType
{
	Type info;
	nodeType<Type> *link;
};

template <class Type>
class linkedListIterator
{
public:
    linkedListIterator();
      //Default constructor
      //Postcondition: current = NULL;

    linkedListIterator(nodeType<Type> *ptr);
      //Constructor with a parameter.
      //Postcondition: current = ptr;

    Type operator*();
      //Function to overload the dereferencing operator *.
      //Postcondition: Returns the info contained in the node.

    linkedListIterator<Type> operator++();    
      //Overload the preincrement operator.
      //Postcondition: The iterator is advanced to the next node.

    bool operator==(const linkedListIterator<Type>& right) const;
      //Overload the equality operator.
      //Postcondition: Returns true if this iterator is equal to 
      //    the iterator specified by right, otherwise it returns
      //    false.

    bool operator!=(const linkedListIterator<Type>& right) const;
      //Overload the not equal to operator.
      //Postcondition: Returns true if this iterator is not equal to
      //    the iterator specified by right, otherwise it returns
      //    false.

private:
    nodeType<Type> *current; //pointer to point to the current
                             //node in the linked list
};


template <class Type>
linkedListIterator<Type>::linkedListIterator()
{
    current = NULL;
}

template <class Type>
linkedListIterator<Type>::
                  linkedListIterator(nodeType<Type> *ptr)
{
    current = ptr;
}

template <class Type>
Type linkedListIterator<Type>::operator*()
{
    return current->info;
}

template <class Type>
linkedListIterator<Type> linkedListIterator<Type>::operator++()   
{
    current = current->link;

    return *this;
}

template <class Type>
bool linkedListIterator<Type>::operator==
               (const linkedListIterator<Type>& right) const
{
    return (current == right.current);
}

template <class Type>
bool linkedListIterator<Type>::operator!=
                 (const linkedListIterator<Type>& right) const
{   return (current != right.current);
}


//***********************************************************
// Author: D.S. Malik
//
// This class specifies the members to implement the basic
// properties of a linked list. This is an abstract class.
// We cannot instantiate an object of this class.
//***********************************************************

template <class Type>
class linkedListType
{
public:
    const linkedListType<Type>& operator=
                         (const linkedListType<Type>&);
      //Overload the assignment operator.

    void initializeList(); 
      //Initialize the list to an empty state.
      //Postcondition: first = NULL, last = NULL, count = 0;

    bool isEmptyList() const;
      //Function to determine whether the list is empty. 
      //Postcondition: Returns true if the list is empty, otherwise
      //    it returns false.

    void print() const;
      //Function to output the data contained in each node.
      //Postcondition: none

    int length() const;
      //Function to return the number of nodes in the list.
      //Postcondition: The value of count is returned.

    void destroyList();
      //Function to delete all the nodes from the list.
      //Postcondition: first = NULL, last = NULL, count = 0;

    Type front() const; 
      //Function to return the first element of the list.
      //Precondition: The list must exist and must not be empty.
      //Postcondition: If the list is empty, the program terminates;
      //    otherwise, the first element of the list is returned.

    Type back() const; 
      //Function to return the last element of the list.
      //Precondition: The list must exist and must not be empty.
      //Postcondition: If the list is empty, the program
      //               terminates; otherwise, the last  
      //               element of the list is returned.

    virtual bool search(const Type& searchItem) const = 0;
      //Function to determine whether searchItem is in the list.
      //Postcondition: Returns true if searchItem is in the list,
      //    otherwise the value false is returned.

    virtual void insertFirst(const Type& newItem) = 0;
      //Function to insert newItem at the beginning of the list.
      //Postcondition: first points to the new list, newItem is
      //    inserted at the beginning of the list, last points to
      //    the last node in the list, and count is incremented by
      //    1.

    virtual void insertLast(const Type& newItem) = 0;
      //Function to insert newItem at the end of the list.
      //Postcondition: first points to the new list, newItem is
      //    inserted at the end of the list, last points to the
      //    last node in the list, and count is incremented by 1.

    virtual void deleteNode(const Type& deleteItem) = 0;
      //Function to delete deleteItem from the list.
      //Postcondition: If found, the node containing deleteItem is
      //    deleted from the list. first points to the first node,
      //    last points to the last node of the updated list, and
      //    count is decremented by 1.

    linkedListIterator<Type> begin();
      //Function to return an iterator at the beginning of the 
      //linked list.
      //Postcondition: Returns an iterator such that current is set
      //    to first.

    linkedListIterator<Type> end();
      //Function to return an iterator one element past the 
      //last element of the linked list. 
      //Postcondition: Returns an iterator such that current is set
      //    to NULL.

    linkedListType(); 
      //default constructor
      //Initializes the list to an empty state.
      //Postcondition: first = NULL, last = NULL, count = 0; 

    linkedListType(const linkedListType<Type>& otherList); 
      //copy constructor

    ~linkedListType();   
      //destructor
      //Deletes all the nodes from the list.
      //Postcondition: The list object is destroyed. 


    int count; //variable to store the number of list elements
                 // 
    nodeType<Type> *first; //pointer to the first node of the list
    nodeType<Type> *last;  //pointer to the last node of the list

private: 
    void copyList(const linkedListType<Type>& otherList); 
      //Function to make a copy of otherList.
      //Postcondition: A copy of otherList is created and assigned
      //    to this list.
}; 

template <class Type>
bool linkedListType<Type>::isEmptyList() const
{
    return (first == NULL);
}

template <class Type>
linkedListType<Type>::linkedListType() //default constructor
{
    first = NULL;
    last = NULL;
    count = 0;
}

template <class Type>
void linkedListType<Type>::destroyList()
{
    nodeType<Type> *temp;   //pointer to deallocate the memory
                            //occupied by the node
    while (first != NULL)   //while there are nodes in the list
    {
        temp = first;        //set temp to the current node
        first = first->link; //advance first to the next node
        delete temp;   //deallocate the memory occupied by temp
    }

    last = NULL; //initialize last to NULL; first has already
                 //been set to NULL by the while loop
    count = 0;
}

template <class Type>
void linkedListType<Type>::initializeList()
{
	destroyList(); //if the list has any nodes, delete them
}

template <class Type>
void linkedListType<Type>::print() const
{
    nodeType<Type> *current; //pointer to traverse the list

    current = first;    //set current so that it points to 
                        //the first node
    while (current != NULL) //while more data to print
    {
        cout << current->info << " ";
        current = current->link;
    }
}//end print

template <class Type>
int linkedListType<Type>::length() const
{
    return count;
}  //end length

template <class Type>
Type linkedListType<Type>::front() const
{   
    assert(first != NULL);

    return first->info; //return the info of the first node	
}//end front

template <class Type>
Type linkedListType<Type>::back() const
{   
    assert(last != NULL);

    return last->info; //return the info of the last node	
}//end back

template <class Type>
linkedListIterator<Type> linkedListType<Type>::begin()
{
    linkedListIterator<Type> temp(first);

    return temp;
}

template <class Type>
linkedListIterator<Type> linkedListType<Type>::end()
{
    linkedListIterator<Type> temp(NULL);

    return temp;
}

template <class Type>
void linkedListType<Type>::copyList
                   (const linkedListType<Type>& otherList) 
{
    nodeType<Type> *newNode; //pointer to create a node
    nodeType<Type> *current; //pointer to traverse the list

    if (first != NULL) //if the list is nonempty, make it empty
       destroyList();

    if (otherList.first == NULL) //otherList is empty
    {
        first = NULL;
        last = NULL;
        count = 0;
    }
    else
    {
        current = otherList.first; //current points to the 
                                   //list to be copied
        count = otherList.count;

            //copy the first node
        first = new nodeType<Type>;  //create the node

        first->info = current->info; //copy the info
        first->link = NULL;        //set the link field of 
                                   //the node to NULL
        last = first;              //make last point to the
                                   //first node
        current = current->link;     //make current point to
                                     //the next node

           //copy the remaining list
        while (current != NULL)
        {
            newNode = new nodeType<Type>;  //create a node
            newNode->info = current->info; //copy the info
            newNode->link = NULL;       //set the link of 
                                        //newNode to NULL
            last->link = newNode;  //attach newNode after last
            last = newNode;        //make last point to
                                   //the actual last node
            current = current->link;   //make current point 
                                       //to the next node
        }//end while
    }//end else
}//end copyList

template <class Type>
linkedListType<Type>::~linkedListType() //destructor
{
   destroyList();
}//end destructor

template <class Type>
linkedListType<Type>::linkedListType
                      (const linkedListType<Type>& otherList)
{
   	first = NULL;
    copyList(otherList);
}//end copy constructor

         //overload the assignment operator
template <class Type>
const linkedListType<Type>& linkedListType<Type>::operator=
                      (const linkedListType<Type>& otherList)
{ 
    if (this != &otherList) //avoid self-copy
    {
        copyList(otherList);
    }//end else

     return *this; 
}

#endif

and here is the cpp file, I put some very small amount of code in it in order to test if the functions in one of the classes in the headers worked. This is the main.cpp file

Code:

#include "graphType.h"
#include <iostream>
using namespace std;
int main()
{
    graphType object;
    object.createGraph();
    return 0;
}

You'll notice that one of the includes in the main file is "graphType.h", This is because the class that contains the object that the main function will access is contained in there. the other header files are the problem and this file is fine and all syntax checks out. the main problem is within the two header files I posted in the beginning of this thread.
graphType.h

Code:

#ifndef H_graph
#define H_graph

#include <iostream>
#include <fstream>
#include <iomanip>
#include "linkedList.h"
#include "unorderedLinkedList.h"
#include "linkedQueue.h"

using namespace std;

class graphType
{
public:
    bool isEmpty() const;
      //Function to determine whether the graph is empty.
      //Postcondition: Returns true if the graph is empty;
      //    otherwise, returns false.

    void createGraph();
      //Function to create a graph.
      //Postcondition: The graph is created using the  
      //    adjacency list representation.

    void clearGraph();
      //Function to clear graph.
      //Postcondition: The memory occupied by each vertex 
      //    is deallocated.

    void printGraph() const;
      //Function to print graph.
      //Postcondition: The graph is printed.

    void depthFirstTraversal();
      //Function to perform the depth first traversal of
      //the entire graph.
      //Postcondition: The vertices of the graph are printed 
      //    using the depth first traversal algorithm.

    void dftAtVertex(int vertex);
      //Function to perform the depth first traversal of 
      //the graph at a node specified by the parameter vertex.
      //Postcondition: Starting at vertex, the vertices are 
      //    printed using the depth first traversal algorithm.

    void breadthFirstTraversal();
      //Function to perform the breadth first traversal of
      //the entire graph.
      //Postcondition: The vertices of the graph are printed 
      //    using the breadth first traversal algorithm.

    graphType(int size = 0); 
      //Constructor
      //Postcondition: gSize = 0; maxSize = size;
      //    graph is an array of pointers to linked lists.

    ~graphType();
      //Destructor
      //The storage occupied by the vertices is deallocated.

protected:
    int maxSize;    //maximum number of vertices
    int gSize;      //current number of vertices
    unorderedLinkedList<int> *graph; //array to create 
                                     //adjacency lists 

private:
    void dft(int v, bool visited[]);
      //Function to perform the depth first traversal of 
      //the graph at a node specified by the parameter vertex.
      //This function is used by the public member functions
      //depthFirstTraversal and dftAtVertex.
      //Postcondition: Starting at vertex, the vertices are 
      //    printed using the depth first traversal algorithm.
};


bool graphType::isEmpty() const
{
    return (gSize == 0);
}

void graphType::createGraph()
{
    ifstream infile;
    char fileName[50];

    int vertex;
    int adjacentVertex;

    if (gSize != 0)	//if the graph is not empty, make it empty
        clearGraph();

    cout << "Enter input file name: ";
    cin >> fileName;
    cout << endl;

    infile.open(fileName);

    if (!infile)
    {
        cout << "Cannot open input file." << endl;
        return;
    }

    infile >> gSize;	//get the number of vertices

    for (int index = 0; index < gSize; index++)
    {
        infile >> vertex;
        infile >> adjacentVertex;

        while (adjacentVertex != -999)
        {
            graph[vertex].insertLast(adjacentVertex);
            infile >> adjacentVertex;
        } //end while
    } // end for

    infile.close();
} //end createGraph

void graphType::clearGraph()
{
    for (int index = 0; index < gSize; index++)
        graph[index].destroyList();

    gSize = 0;
} //end clearGraph

void graphType::printGraph() const
{
    for (int index = 0; index < gSize; index++)
    {
        cout << index << " ";
        graph[index].print();
        cout << endl;
    }

    cout << endl;
} //end printGraph

void graphType::depthFirstTraversal()
{
    bool *visited; //pointer to create the array to keep 
                   //track of the visited vertices
    visited = new bool[gSize];

    for (int index = 0; index < gSize; index++) 
        visited[index] = false;
	
        //For each vertex that is not visited, do a depth 
        //first traverssal
    for (int index = 0; index < gSize; index++)	
        if (!visited[index]) 
            dft(index,visited);
    delete [] visited;
} //end depthFirstTraversal

void graphType::dft(int v, bool visited[])
{
    visited[v] = true;
    cout << " " << v << " ";  //visit the vertex

    linkedListIterator<int> graphIt;

        //for each vertex adjacent to v
    for (graphIt = graph[v].begin(); graphIt != graph[v].end();
                                     ++graphIt)
    {
        int w = *graphIt;
        if (!visited[w])
            dft(w, visited);
    } //end while
} //end dft

void graphType::dftAtVertex(int vertex)
{
    bool *visited;

    visited = new bool[gSize];

    for (int index = 0; index < gSize; index++)
        visited[index] = false;

    dft(vertex, visited);

    delete [] visited;
} // end dftAtVertex


void graphType::breadthFirstTraversal()
{
    linkedQueueType<int> queue;

    bool *visited;
    visited = new bool[gSize];

    for (int ind = 0; ind < gSize; ind++)
        visited[ind] = false;	//initialize the array 
                                //visited to false

    linkedListIterator<int> graphIt;

    for (int index = 0; index < gSize; index++)
        if (!visited[index])
        {
            queue.addQueue(index);
            visited[index] = true;
            cout << " " << index << " ";

            while (!queue.isEmptyQueue())
            {
                int u = queue.front();
                queue.deleteQueue();

                for (graphIt = graph[u].begin(); 
                     graphIt != graph[u].end(); ++graphIt)
                {
                    int w = *graphIt;
                    if (!visited[w])
                    {
                        queue.addQueue(w);
                        visited[w] = true;
                        cout << " " << w << " ";
                    }
                }
            } //end while
        }
		
    delete [] visited;
} //end breadthFirstTraversal

    //Constructor
graphType::graphType(int size)
{
    maxSize = size;
    gSize = 0;
    graph = new unorderedLinkedList<int>[size];
}

    //Destructor
graphType::~graphType()
{
    clearGraph();
}

#endif

This file is working fine, something in the unorderedLinkedList.h file has an issue. all of the error prompts are telling me that the variables that the functions in that header file contains aren't declared inside of the class.

baronobeefdip · 04-29-2014, 07:05 PM

I was able to shrink the amount of errors I was getting by taking these lines

Code:

int count; //variable to store the number of list elements
                 // 
    nodeType<Type> *first; //pointer to the first node of the list
    nodeType<Type> *last;  //pointer to the last node of the list

inside of the linkedList.h's linkedListType class and placing it in the unorderedLinkedList class. I am getting less errors (I'm not sure if this is a wise thing to do) but nonetheless I am still getting errors. the error I am getting is this.

Code:

g++ ajllab10.cpp -o lab10
In file included from graphType.h:16:0,
                 from ajllab10.cpp:1:
unorderedLinkedList.h: In member function ‘bool unorderedLinkedList<Type>::search(const Type&) const [with Type = int]’:
ajllab10.cpp:8:1:   instantiated from here
unorderedLinkedList.h:58:5: error: cannot convert ‘nodeType<int>’ to ‘nodeType<int>*’ in assignment
make: *** [lab10] Error 1

How am I supposed to fix this one?

John VV · 04-29-2014, 07:18 PM

what compiler are you using ?

gcc 4.8 is more strict than 4.7
and 4.7 is more strict than 4.3 or 4.1

if 4.8 dose the code build in gcc 4.7 or 4.3

ntubski · 04-29-2014, 07:54 PM

Just like the error message says, don't assign a value to an pointer; take out the * before first.

For the first problem, see [35.19] Why am I getting errors when my template-derived-class uses a member it inherits from its template-base-class?

johnsfine · 04-30-2014, 07:26 AM

Quote:

Originally Posted by baronobeefdip

the compiler claims that the variables that I am trying to use inside of some of the functions are not being declared in the scope. I setup the inheritance

Inheritance from a templated class in C++ works semantically, but not syntactically. You can find the underlying principles documented in many places. But I find it easier to just deal with the problems it causes, rather than worry about the C++ language design fundamentals that make C++ work this way.

Code:

template <class Type>
class unorderedLinkedList: public linkedListType<Type>
{

My preferred solution is to insert right after the above:

Code:

  typedef linkedListType<Type> super;
  using super::first;
  using super::count;
  using super::last;

1) As a matter of personal coding style (after finding the corresponding built-in feature of Java very helpful), whenever the most important base class is either templated or likely to change as the code evolves, I make a typedef giving the name super to that most important base class (which base class is most important is on rare occasion a programmer judgment call). Then I never refer to that base class as itself again in this class. I always refer to it as super.

2) If the base class is templated, I then use using as above to pull the variables and functions of the base class that I need into the current scope. For a non templated base class, they are already in scope.

Even for a templated base class, those names are kind of in scope. Many other people use a different solution to this problem, that I consider ugly. Everywhere you currently reference first, instead reference this->first
So you don't really need anything to bring those names into scope, you just need to syntactically tell the compiler those names are expected to be in the class scope. A third solution, having defined super as I did but without my use of using, you could replace each use of first by super::first. Without a typedef for super, some uses of first can be replaced by linkedListType<Type>::first but generally that is a flawed approach. I find all the other solutions to this problem (other than the one I recommended first) get very ugly very fast in real programs.

I like the construct super::name to be used only in the situation that name has been redefined in the current class and you have reason in the current class to want to access the one in the base class.

Quote:

Originally Posted by baronobeefdip

I was able to shrink the amount of errors I was getting by taking these lines

Code:

int count; //variable to store the number of list elements
                 //
    nodeType<Type> *first; //pointer to the first node of the list
    nodeType<Type> *last;  //pointer to the last node of the list

inside of the linkedList.h's linkedListType class and placing it in the unorderedLinkedList class.

That is a terrible idea!

You are defeating the entire purpose for having a base class. If you use any function from the base class, your code is probably broken. But even if the code works, it is wrong.

Quote:

Originally Posted by ntubski

Just like the error message says, don't assign a value to an pointer; take out the * before first.

For the first problem, see [35.19] Why am I getting errors when my template-derived-class uses a member it inherits from its template-base-class?

I can't guess at the exact code the OP compiled to get the error message quoted. So I can't find line 58 and I can't see why that error message would occur. I especially can't see which * you want removed from which use of the name first

The * in the declaration of first is correct and should not be removed. I didn't find another use of first with a * before it.

The link you provided gives a more technically correct description of the cause of the apparent inheritance problem than I chose to give. But it provides bad suggestions for the work around. When you hit one of these errors, I understand it feels incrementally easier to fix it at the point where it occurs. But a large project will be much more maintainable if you fix all of them (for a given class) with using lines kept together withing the class definition.