Pointer based lists ????????

[LiverEatnJohnson]

Again its me being new to c++. I get segmentation errors and i just plane dont understand pointer lists yet.

/*******************************************
 * Project:    GrocceyList
 * File:       GrocieItem.h
 * Author:     Jeremiah Johnson
 * Assginment: CH3 PP2
 * Date:       September 27, 2011, 10:23 PM
 *******************************************/

#ifndef GROCIEITEM_H
#define	GROCIEITEM_H

#include <string>

using namespace std;

/**
 * Grocie Item header.
 */
class GI {
public:

    /**
     * Constroctor for Grocie Item.
     */
    GI();

    /**
     * Deconstroctor for Grocei Item.
     */
    ~GI();

    /**
     * Sets the name of a Groce Item.
     * @param thing, name of the thing to be added.
     */
    void setName(string thing);

    /**
     * Retruns the name of the Grocie Item.
     * @return string, name of the item
     */
    string getName();

private:

    string name;

};

#endif
/* GROCIEITEM_H */

/*******************************************
 * Project:    GrocceyList
 * File:       GrocieItem.cpp
 * Author:     Jeremiah Johnson
 * Assginment: CH3 PP2
 * Date:       September 27, 2011, 10:23 PM
 *******************************************/

#include "GrocieItem.h"
#include <string>
// Variables //
string name;

// Methods //
/**
 * Constroctor for Grocie Item.
 */
GI::GI() {
    name = "Unamed";
}

/**
 * Deconstroctor for Grocei Item.
 */
GI::~GI() {
    delete this;
}

/**
 * Sets the name of a Groce Item.
 * @param thing, name of the thing to be added.
 */
void GI::setName(string thing) {
    name = thing;
}

/**
 * Retruns the name of the Grocie Item.
 * @return string, name of the item
 */
string GI::getName() {
    return name;
}

/*******************************************
 * Project:    GrocceyList
 * File:       GroceiNode.h
 * Author:     Jeremiah Johnson
 * Assginment: CH3 PP2
 * Date:       September 27, 2011, 10:22 PM
 *******************************************/

#ifndef GROCEINODE_H
#define	GROCEINODE_H

#include <string>

using namespace std;

/**
 * Grocie Node header.
 */
class GN {
public:

    /**
     * Construcrot for a grocie node
     */
    GN();

    /**
     * Deconstroctor for a grocie node
     */
    ~GN();

    /**
     * Adds item thing as a grocei item.
     * @param thing
     */
    void GI(string thing);

    GN *next;

};

#endif	/* GROCEINODE_H */

/*******************************************
 * Project:    GrocceyList
 * File:       GrocieNode.cpp
 * Author:     Jeremiah Johnson
 * Assginment: CH3 PP2
 * Date:       September 27, 2011, 10:22 PM
 *******************************************/

#include "GroceiNode.h"
#include <string>

/**
 * Construcrot for a grocie node
 */
GN() {

}

/**
 * Deconstroctor for a grocie node
 */
~GN() {

}

/**
 * Adds item thing as a grocei item.
 * @param thing
 */
void GI(string thing) {

}

/*******************************************
 * Project:    GrocceyList
 * File:       GrocieList.h
 * Author:     Jeremiah Johnson
 * Assginment: CH3 PP2
 * Date:       September 27, 2011, 10:22 PM
 *******************************************/

#ifndef GROCIELIST_H
#define	GROCIELIST_H

#include <string>

using namespace std;

/**
 * Grocie List header
 */
class GL {
public:

    /**
     * Constructor for the GrocieList or GL class.
     */
    GL();

    /**
     * Deconstructor for the GrocieList or GL class.
     */
    ~GL();

    /**
     * Inserts a new item into the grocie list.
     * @param thing, being inserted.
     * @return bool, weather or not thing was inserted.
     */
    bool insert(int spot);

    /**
     * Removes thing from the grocie list.
     * @param thing, being removed.
     * @return bool, weather or not thing was removed.
     */
    bool remove(string thing);

    /**
     * Retrives thing at spot pos from grocie list.
     * @param pos, spot thing is being retrived from.
     * @return bool, weather or not thing was retrived.
     */
    bool retrive(int pos);

    /**
     * Returns the lenght of the grocie list.
     * @return int, representing the lenght of the grocie list.
     */
    int length();

    /**
     * Returns weather or not the grocie list is empty.
     * @return bool, weather or not the grocie list is empty.
     */
    bool isEmpty();

private:

    GN *head;

};

#endif
/* GROCIELIST_H */

/*******************************************
 * Project:    GrocceyList
 * File:       GrocieList.cpp
 * Author:     Jeremiah Johnson
 * Assginment: CH3 PP2
 * Date:       September 27, 2011, 10:22 PM
 *******************************************/

#include "GrocieList.h"

// Variables //
int &head;

// Methods //
/**
 * Constructor for the GrocieList or GL class.
 */
GL::GL() {
    
}

/**
 * Deconstructor for the GrocieList or GL class.
 */
GL::~GL() {

}

/**
 * Inserts a new item into the grocie list.
 * @param thing, being inserted.
 * @return bool, weather or not thing was inserted.
 */
GL::insert(string thing) {

}

/**
 * Returns weather or not the grocie list is empty.
 * @return bool, weather or not the grocie list is empty.
 */
GL::isEmpty() {

}

/**
 * Returns the lenght of the grocie list.
 * @return int, representing the lenght of the grocie list.
 */
GL::length() {

}

/**
 * Removes thing from the grocie list.
 * @param thing, being removed.
 * @return bool, weather or not thing was removed.
 */
GL::remove(string thing) {

}

/**
 * Retrives thing at spot pos from grocie list.
 * @param pos, spot thing is being retrived from.
 * @return bool, weather or not thing was retrived.
 */
GL::retrive(int pos) {

}

/*******************************************
 * Project:    GrocceyList
 * File:       main.cpp
 * Author:     Jeremiah Johnson
 * Assginment: CH3 PP2
 * Date:       September 27, 2011, 10:23 PM
 *******************************************/

#include <cstdlib>
#include <string>
#include <iostream>
#include "GroceiNode.h"
#include "GrocieItem.h"
#include "GrocieList.h"

using namespace std;

/**
 * Program allows the user to create a grocie list with a text based interface.  The list can be
 * any length.
 */
int main() {

    string name;
    GI item;

    cin >> name;
    cout << endl;

    item.setName(name);


    cout << item.getName();

    return 0;
}

output:

g++    -c -g -MMD -MP -MF build/Debug/GNU-Linux-x86/GroceiNode.o.d -o build/Debug/GNU-Linux-x86/GroceiNode.o GroceiNode.cpp
GroceiNode.cpp:15: error: expected unqualified-id before ‘)’ token
GroceiNode.cpp:22: error: declaration of ‘~GN’ as non-member
make[2]: *** [build/Debug/GNU-Linux-x86/GroceiNode.o] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
make[2]: Leaving directory `/home/bullfrog/NetBeansProjects/CnCpp/GrocceyList'
make[1]: Leaving directory `/home/bullfrog/NetBeansProjects/CnCpp/GrocceyList'

BUILD FAILED (exit value 2, total time: 211ms)

[zb0S216C]

LiverEatnJohnson wrote:

delete this; (sic)

This is dangerous; handle this with care. Deleting an object that was never dynamically allocated can cause segmentation errors. Only an object that called new can use delete.

Which part of linked-lists don't you understand?

_Wazzak

[ne555]

Those are compiler errors
GN::GN(){ like you did with GI and GL (by the way, use descriptive names)

GI::~GI() {
    delete this;
}

It's dangerous to perform suicide, you could die. (stack overflow)

Really, there is a conceptual error there.
The destructor should be used to release resources. By instance when a fstream dies, it commits pending changes and it closes the file

[LiverEatnJohnson]

Ok i think in the end the GI will be dynamicly declared cause i dont want the list to have a limit Thanks for the help that is probly why i am getting segmentation errors now. I will try dynamicly allocating it.

[LiverEatnJohnson]

What i dont understand is how to program the node and list to contain items. like what to put in the methods

[Azagaros]

I will give what I would have in the two classes:

class LinkListNode
{
public:
      // my data I would want to keep..
      int someNumber;
      string someString;

     // I am assuming I have a singly linked list.
     LinkedListNode* nextNode;
     LinkedListNode()
     {
           someNumber = 0;
           nextNode = NULL;
     }
};

class LinkedListContainer
{
private:
         LinkedListNode *headofList;
         int numberOfNodes;
public:
         LinkedListContainer()
         {
               headofList = NULL;
               numberOfNode = 0;
         }
         ~LinkedListContainer()
         {
                // clean up the list on destruction.
                LinkListNode* currentNode = headofList ;
                LinkedListNode* deleteNode = headofList;
          
                while(currentNode != NULL)
                {
                          deleteNode = currentNode;
                          currentNode = currentNode->nextNode;
                          delete deleteNode;
                }
          }

         // for appending to the end of list
         LinkListNode* appendToList(LinkListNode* newNode);

         // for inserting a node to a list, a node and a location as an integer
         LinkListNode* InsertAt(LinkListNode* newNode, int Index);

         // searching the list
         LinkListNode* Search(string searchString);
         LinkListNode* Search(int searchNumber);

         // counting the list;
         int CountNodes();

         // deleting all
         void DeleteAll();
         // deleting at some count down the list
         void DeleteAt(int deleteat);
         // delete Node // this one needs to search the list for the node to fix links
         void DeleteNode(LinkedListNode* deleteNode);

         // returning one at some count down the list.
         LinkedListNode* GetAt(int numberCount); 
};

I hope this is some food for thought

[LiverEatnJohnson]

Thanks to everyone who helped me it works now if anyone wants the source code let me know.