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Passing Linked list into function

Posted on 2009-07-04
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Last Modified: 2013-11-17
I have a homework assignment to write an address list using a linked list.  I am having a problem passing the list into a function.  I know I want to pass by reference.  in my menu program below, I pass the list into the function "newentry", but when I return to the menu and print the list it is empty.

Please help.
#include <iostream>

#include <string>

using namespace std;

#include "menu.h"
 

void main()

{

	mainmenu();

}
 

void mainmenu()

{

	SortedType list;

	AddrType address;

	int select;
 

	cout << "Enter your selection: " << endl << endl;

	cout << "(1) New entry " << endl;

	cout << "(2) Delete an entry " << endl;

	cout << "(3) Edit an entry " << endl;

	cout << "(4) Generate a birthday card " << endl;

	cout << "(5) Generate an aniversary card " << endl;

	cout << "(6) Print List " << endl;

	cout << "(7) Exit program " << endl;
 

	cin >> select;
 
 

	switch (select)

	{

		case 1:

			//cout << "New Entry" << endl;

			newentry(list);

			break;

		case 2:

			cout << "Delete an entry" << endl;

			break;

		case 3:

			cout << "Edit an entry" << endl;

			break;

		case 4:

			cout << "Generate BDay Card" << endl;

			break;

		case 5:

			cout << "Gen Aniversay Card" << endl;

			break;

		case 6:

			//cout << "Print List" << endl;

			PrintList(list);

			break;

		case 7:

			cout << "Exit" << endl;

			break;

		default:

			cout << "Enter a number from 1-6: " << cout << endl;

			mainmenu();

	}

}

void newentry(SortedType& list)

{

	string fname;

	string lname;

	string addr;

	int bday;

	int aniv;

	AddrType address;

	cout << "Enter First Name: ";

	cin >> fname;

	address.initfname(fname);

	cout << fname << endl;

	cout << "Enter Last Name: ";

	cin >> lname;

	address.initlname(lname);

	cout << lname << endl;

	cout << "Enter Address: ";

	fflush(stdin);

	getline(cin, addr);

	address.initaddress(addr);

	cout << addr << endl;

	cout << "Enter Birthday: ";

	cin >> bday;

	address.initbday(bday);

	cout << bday << endl;

	cout << "Enter Aniversary: ";

	cin >> aniv;

	address.initaniv(aniv);

	cout << aniv << endl;

	list.InsertItem(address);

/*

	int length;

	AddrType address2;

	list.ResetList();

	cout << "List" << endl;

	length = list.GetLength();

	for (int counter = 1; counter <= length; counter++)

	{

		list.GetNextItem(address2);

		address2.PrintFirst(cout);

		cout << endl;

		address2.PrintLast(cout);

		cout << endl;

		address2.PrintBday(cout);

		cout << endl;

		address2.PrintAniv(cout);

		cout << endl;

	}

*/
 

	mainmenu();
 

}

void PrintList(SortedType &list)

{

	int length;

	AddrType address;

	list.ResetList();

	cout << "List" << endl;

	length = list.GetLength();

	for (int counter = 1; counter <= length; counter++)

	{

		list.GetNextItem(address);

		address.PrintFirst(cout);

		cout << endl;

		address.PrintLast(cout);

		cout << endl;

		address.PrintBday(cout);

		cout << endl;

		address.PrintAniv(cout);

		cout << endl;

	}

}

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Comment
Question by:rsissick
  • 4
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9 Comments
 
LVL 44

Expert Comment

by:AndyAinscow
ID: 24776802
void PrintList(SortedType &list)
{
        int length;
        AddrType address;
        list.ResetList();       <<---------------------------


Does that empty the list?  

0
 

Author Comment

by:rsissick
ID: 24777346
No, but I kinda figured someone would ask me that.  It just resets the current pos pointer to NULL.  

Thanks

void SortedType::ResetList()
{
  currentPos = NULL;
}

void SortedType::GetNextItem(AddrType& item)
{
  if (currentPos == NULL)
    currentPos = listData;
  item = currentPos->info;
  currentPos = currentPos->next;

}
0
 
LVL 44

Expert Comment

by:AndyAinscow
ID: 24777374
void newentry(SortedType& list)
{
...
mainmenu();  <<---  This will generate a NEW list.

You need a loop in the main function
0
 
LVL 40

Accepted Solution

by:
evilrix earned 250 total points
ID: 24777392
newentry calls mainmenu at the end, so it's not returning it's actually starting a new callstack, which creates a new version of your list in that callstack context. You do the same in the dwefault of your switch. You'll eventually get a stack overflow doing this.

See my comments below...
#include <iostream>

#include <string>

using namespace std;

#include "menu.h"

 

void main()

{

        mainmenu();

}

 

void mainmenu()

{

        SortedType list;

        AddrType address;

        int select;

 

        cout << "Enter your selection: " << endl << endl;

        cout << "(1) New entry " << endl;

        cout << "(2) Delete an entry " << endl;

        cout << "(3) Edit an entry " << endl;

        cout << "(4) Generate a birthday card " << endl;

        cout << "(5) Generate an aniversary card " << endl;

        cout << "(6) Print List " << endl;

        cout << "(7) Exit program " << endl;

 

        cin >> select;

 

 

        switch (select)

        {

                case 1:

                        //cout << "New Entry" << endl;

                        newentry(list);

                        break;

                case 2:

                        cout << "Delete an entry" << endl;

                        break;

                case 3:

                        cout << "Edit an entry" << endl;

                        break;

                case 4:

                        cout << "Generate BDay Card" << endl;

                        break;

                case 5:

                        cout << "Gen Aniversay Card" << endl;

                        break;

                case 6:

                        //cout << "Print List" << endl;

                        PrintList(list);

                        break;

                case 7:

                        cout << "Exit" << endl;

                        break;

                default:

                        cout << "Enter a number from 1-6: " << cout << endl;

                        mainmenu(); //<---------------------------------------------RX: [ REMOVE THIS ]

        }

}

void newentry(SortedType& list)

{

        string fname;

        string lname;

        string addr;

        int bday;

        int aniv;

        AddrType address;

        cout << "Enter First Name: ";

        cin >> fname;

        address.initfname(fname);

        cout << fname << endl;

        cout << "Enter Last Name: ";

        cin >> lname;

        address.initlname(lname);

        cout << lname << endl;

        cout << "Enter Address: ";

        fflush(stdin);

        getline(cin, addr);

        address.initaddress(addr);

        cout << addr << endl;

        cout << "Enter Birthday: ";

        cin >> bday;

        address.initbday(bday);

        cout << bday << endl;

        cout << "Enter Aniversary: ";

        cin >> aniv;

        address.initaniv(aniv);

        cout << aniv << endl;

        list.InsertItem(address);

/*

        int length;

        AddrType address2;

        list.ResetList();

        cout << "List" << endl;

        length = list.GetLength();

        for (int counter = 1; counter <= length; counter++)

        {

                list.GetNextItem(address2);

                address2.PrintFirst(cout);

                cout << endl;

                address2.PrintLast(cout);

                cout << endl;

                address2.PrintBday(cout);

                cout << endl;

                address2.PrintAniv(cout);

                cout << endl;

        }

*/

 

        mainmenu(); //<---------------------------------------------RX: [ REMOVE THIS ]

 

}

void PrintList(SortedType &list)

{

        int length;

        AddrType address;

        list.ResetList();

        cout << "List" << endl;

        length = list.GetLength();

        for (int counter = 1; counter <= length; counter++)

        {

                list.GetNextItem(address);

                address.PrintFirst(cout);

                cout << endl;

                address.PrintLast(cout);

                cout << endl;

                address.PrintBday(cout);

                cout << endl;

                address.PrintAniv(cout);

                cout << endl;

        }

}

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LVL 40

Expert Comment

by:evilrix
ID: 24777395
Andy, it seems we simul-posted :)
0
 
LVL 44

Expert Comment

by:AndyAinscow
ID: 24777423
@evilrix - No problems
0
 

Author Comment

by:rsissick
ID: 24782148
I understand.  I want the menu to be displayed after the new item is entered.  How do I do this without calling my menu function again?
0
 
LVL 44

Assisted Solution

by:AndyAinscow
AndyAinscow earned 250 total points
ID: 24782906
As I said - you use a loop
(ps. For homework we are limited with what we can write due to EE rules)

foo()
{
  MyList list;
  while(TRUE)
  {
    //display options
    //process input
    foo2(list);    //here the ONE instance of list is processed
  }
}
0
 

Author Closing Comment

by:rsissick
ID: 31599760
Thank so much!
0

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