PROGRAM 39


//  FILE NAME:  PROG39.CPP     PROGRAMMER NAME:  ANTHONY F. ORTIZ
//  THIS PROGRAM USES A CLASS CALLED LINK LIST.  THE MEMBER FUNCTIONS
//  INITIALIZE THE COUNT AND LINKLIST OBJECT, ENTER OBJECTS FROM THE
//  KEYBOARD, AND DISPLAY TOTAL, AVERAGE, AND COUNT OF THE OBJECTS.

#include "linklist.h"

print_menu ();
char get_selection (linklist & expenses);
pause_program ();

int main ()
{
    char choice;
    linklist expenses;
    do
    {
        print_menu ();
        choice = get_selection (expenses);
    }
    while (choice != 'Q');
    return 0;
}

print_menu ()
{
    clrscr ();
    gotoxy (25, 1);
    cout << "MENU OPTIONS";
    gotoxy (30, 3);
    cout << "E -- ENTER OBJECT";
    gotoxy (30, 4);
    cout << "T -- PRINT COUNT";
    gotoxy (30, 5);
    cout << "Q -- QUIT PROGRAM";
    gotoxy (25, 7);
    cout << "ENTER SELECTION ";
    return 0;
}

char get_selection (linklist & expenses)
{
    char choice;
    cin >> choice;
    choice = toupper (choice);
    switch (choice)
    {
        case ('E'):  {
                         expenses.enteritem ();
                         break;
                     }
        case ('T'):  {
                         expenses.printtotal ();
                         pause_program ();
                         break;
                     }
        case ('Q'):  {
                         clrscr ();
                         break;
                     }
    }
    return (choice);
}

pause_program ()
{
    cout << endl << "PRESS ENTER KEY TO CONTINUE ..... ";
    getch ();
    return 0;
}

//  FILE NAME:  LINKLIST.H
//  THIS FILE CONTAINS THE DECLARATION OF THE LINKLIST CLASS.

#ifndef linklist_h
#define linklist_h

#include 
#include 
#include 
#include 
#include 

typedef float data;

struct node
{
    data listdata;
    node * link;
};

class linklist
{
    protected:
        node * head;
        int count;

    public:
        linklist ();
        //  POST:  CONSTRUCTOR, THE LINKLIST OBJECT IS INITIALIZED TO AN EMPTY LIST.

        ~linklist ();
        //  POST:  DESTRUCTOR, THE LINKLIST OBJECT  IS DEALLOCATED.

        void enteritem ();
        //  POST:  PROMPTS FOR DATA ITEM FROM THE KEYBOARD TO ENTER INTO THE LIST;
        //         ITEM IS ADDED TO THE BEGINNING OF THE LIST VIA MEMBER FUNCTION
        //         ADD (ITEM).

        void printtotal (void);
        //  POST:  PRINTS THE TOTAL OF ALL CURRENT ENTRIES.  ALSO PRINTS THE CURRENT
        //         COUNT AND AVERAGE.

        void viewlist (void);
        //  POST:  DISPLAY CURRENT LIST WITH POSITION NUMBERS 1, 2, 3, ..., COUNT.

        void changelist (void);
        //  POST:  THIS FUNCTION IS TO CALL VIEWLIST AUTOMATICALLY WHEN INVOKED.
        //         USER SHOULD BE ABLE TO 'CANCEL' WITHOUT MAKING ANY CHANGES IF
        //         DESIRED.  THERE WILL BE TWO POSSIBLE CHANGES:
        //         A)  USER MAY ENTER A NEW ITEM TO REPLACE AN EXISTING ITEM OF THEIR
        //             CHOICE.
        //         B)  USER MAY DELETE AN ITEM FROM THE LIST.

        void add (data item);
        //  POST:  ADDS A NODE TO THE HEAD OF THE LIST.

        void del ();
        //  POST:  DELETES THE POINTER TO THE FIRST NODE IN THE LIST.  PRESUMES THE
        //         LIST IS NOT EMPTY.

        void delall ();
        //  POST:  DELETES ALL POINTERS TO THE NODES IN THE LIST.  USES THE DEL ()
        //         FUNCTION.  USED BY THE DESTRUCTOR.
};

#include "linklist.cpp"
#endif

//  FILE NAME:  LINKLIST.CPP
//  THIS FILE CONTAINS THE IMPLEMENTATION OF THE CLASS LINKLIST.

linklist :: linklist ()
{
    head = 0;
    count = 0;
    cout << "CONSTRUCTOR INVOKED." << endl << endl;
    cout.setf (ios :: showpoint);
    cout.setf (ios :: fixed);
    cout << setprecision (2);
}

linklist :: ~linklist ()
{
    delall ();
    cout << "DESTRUCTOR INVOKED" << endl << endl;
}

void linklist :: enteritem (void)
{
    data item;
    clrscr ();
    cout << "ENTER A OBJECT. ";
    cin >> item;
    add (item);
    count++;
}

void linklist :: printtotal (void)
{
    float sum, average;
    sum = average = 0;
    clrscr ();
    for (node * p = head; p != 0; p = p -> link)
    {
        sum = sum +  p -> listdata;
    }
    average = sum / count;
    cout << "THE TOTAL IS " << sum << ".  THE AVERAGE IS " << average;
    cout << ".  THE COUNT IS " << count << "." << endl;
}

void linklist :: viewlist (void)
{
    int count2 = 1;
    clrscr ();
    cout << "HERE ARE ALL THE OBJECTS OF THE LIST: " << endl << endl;
    for (node * p = head; p != 0; p = p -> link)
    {
        cout << "OBJECT " << setw (2) << count2 << ": " << setw (8);
        cout << p -> listdata << endl;
        count2++;
    }
}

//  THIS MEMBER FUNCTION IS STILL UNDER CONSTRUCTION.
void linklist :: changelist (void)
{
    char choice, ans;
    int position, count2;
    data change;
    clrscr ();
    gotoxy (25, 1);
    cout << "MENU CHOICES";
    gotoxy (30, 3);
    cout << "D -- DELETE AN ITEM";
    gotoxy (30, 4);
    cout << "C -- CHANGE AN ITEM";
    gotoxy (25, 6);
    cout << "ENTER A CHOICE: ";
    cin >> choice;
    choice = toupper (choice);
    if (choice == 'D' || choice == 'C')
    {
        clrscr ();
        do
        {
            cout << "ENTER A # FROM 1 .. " << count;
            cout << " TO CHANGE AN ITEM. ";
            cin >> position;
            cout << endl;
        }
        while (position < 1 || position > count);
    }
    count2 = 1;
    for (node * p = head; p != 0; p = p -> link)
    {
        if (count2 == position)
        {
            break;
        }
        count2++;
    }
    switch (choice)
    {
        case ('D'):  {
                         clrscr ();
                         cout << "DELETE OBJECT " << position << " ";
                         cout << p -> listdata << " (Y/N)? ";
                         cin >> ans;
                         ans = toupper (ans);
                         if (ans == 'Y')
                         {
                             node * prevptr;
                             if (p == head)
                             {
                                 head = head -> link;
                             }
                             else
                             {
                                 prevptr = head;
                                 while (prevptr -> link != p)
                                 {
                                     prevptr = prevptr -> link;
                                 }
                                 prevptr -> link = p -> link;
                             }
                             delete p;
                             count--;
                             cout << endl << "OBJECT DELETED " << endl;
                         }
                         else
                         {
                             cout << endl << "OBJECT NOT DELETED" << endl;
                         }
                         break;
                     }
        case ('C'):  {
                         clrscr ();
                         cout << "ENTER NEW OBJECT " << position << ": ";
                         cin >> change;
                         cout << endl << "CHANGE OBJECT " << position;
                         cout << " " << p -> listdata << " (Y/N)? ";
                         cin >> ans;
                         ans = toupper (ans);
                         if (ans == 'Y')
                         {
                             p -> listdata = change;
                             cout << endl << "OBJECT CHANGED" << endl;
                         }
                         else
                         {
                             cout << endl << "OBJECT NOT CHANGED" << endl;
                         }
                         break;
                     }
    }
}

void linklist :: add (data item)
{
    node * temp = new node;
    temp -> link = head;
    temp -> listdata = item;
    head = temp;
}

void linklist :: del ()
{
    node * temp = head;
    head = temp -> link;
    delete temp;
    count--;
}

void linklist :: delall ()
{
    while (head != 0)
    {
        del ();
    }
}

//  OUTFILE:  PROG39.OUT

MENU OPTIONS
                                                                                
    E -- ENTER OBJECT
    T -- PRINT COUNT                                   
    Q -- QUIT PROGRAM                                  
                                                                                
ENTER SELECTION q                                       
DESTRUCTOR INVOKED




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