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Why i cannot create third variable

Felicia123 (260)
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#include <iostream>
#include <string>

using namespace std;

class Vending{
private:
	string item[4];
	double coin;
public:

	Vending();

	void showItemMenu();
	void insertCoin();
	void buyItem();
};

vending.h

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#include "vending.h"

Vending::Vending() {
    coin = 0.00;
    item[0] = "Coffee";
    item[1] = "Snack";
    item[2] = "Cans of soda";
    item[3] = "hot drinks";
    item[4] = "ice cream";
    
}

void Vending::showItemMenu(){
    cout << "\tWelcome to Lim's Vending Machine" << endl
         << "--------------------------------------------------" << endl;
    for( int i = 0 ; i < 5 ; i++ ){
        cout << ( i+1 ) << ". " << item[i] << endl;
    }
}

void Vending::insertCoin(){
    cout << "Please insert RM 5 for each item : RM";
    double money = 0.00;
    double moremoney = 0.00;
    double tmp = 0.00;
    cin  >> money;
    if( money < 5 && money > 0 ){
        do{
            tmp = 5 - money;
            cout << "Please insert more RM" << tmp << " !" << endl
                 << "Insert more money : RM";
            cin  >> moremoney;
            money+= moremoney;
   
        }while( money < 5 && money > 0);
        if( money > 5 ){
            tmp = 0.00;
            tmp = money - 5;
            cout << "Here is your change : RM" << tmp << endl;
            buyItem();
        }
        else
            buyItem();
    }
    else if( money > 5 ){
        tmp = money - 5;
        cout << "Here is your change : RM" << tmp << endl;
        buyItem();
    }
}

void Vending::buyItem(){
    
    cout << endl;
    cout << "Choose item : ";
    int itemChoice = 0;
    cin  >> itemChoice;
    if( itemChoice < 1 || itemChoice > 5 ){
        do{
            cout <<"Invalid input ! Please re-enter";
            cin  >> itemChoice;
        }while(itemChoice < 1 || itemChoice > 5 );
    }
    switch( itemChoice ){
        case 1:
            cout << "Here is your Coffee" << endl
                 << "Thanks you ! Please come again !" << endl << endl;
            break;
        case 2:
            cout << "Here is your Snack" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        case 3:
            cout << "Here is your Soda" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        case 4:
            cout << "Here is your hot Drinks" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        case 5:
            cout << "Here is your ice cream" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        default:
            cout << "Invalid input!";       
    }
}

vending.cpp



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/* 
 * File:   main.cpp
 * Author: Lim
 *
 * Created on March 12, 2013, 1:19 PM
 */

#include "vending.h"


int main( ) {

    Vending theVending;
   
    theVending.showItemMenu();
   // theVending.insertCoin();

	system( "pause" );
    return 0;
}

main.cpp


why i cannot create third variable inside my private data

if i create my program will stop run.
else i cannot run.
and why i cannot delete the virtual constructor and the another constructor?

if i delete them my program will stop working window pop out ! my lecturer also cannot solve the program !
Last edited on
MiiNiPaa (8886)
item[4] = "ice cream";
You accessing out of bounds here. Your item array declared as char item[4][20]; so you can hold 4 c-strings here with indexes 0, 1, 2 and 3.
Felicia123 (260)
@miniioaa.change it to string.

my default program are string. paste wrong here. but can't work also
MiiNiPaa (8886)
That will not change fact that you are accessing out of bounds. Even if it is string item[4]; largest index is 3: item[3]

item[4] will access random memory and can corrupt it (write a garbage to another member for example)
Last edited on
TheIdeasMan (6781)
You should really have a private member:

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static const unsigned SIZE = 5;
string item[SIZE];


rather than 5 everywhere throughout your code.

Line 17 in the showItemMenu function segfaults because you add 1 in the body of the loop - which takes you out of bounds for the array again.

In the insertCoin function be careful comparing doubles - you loops might not run the correct number of times, because of the way that doubles are stored.

I also don't like do loops, because you have the test twice on lines 28 & 35 and 58 & 62.

It doesn't make sense for the if on lines 36 to 41 to be inside the If on line 27 because it will never be true & is unreachable code. You have it duplicated on lines 45 - 49.

Also a quit option in your switch.

If you enclose the switch in a while loop that uses bool Quit variable, bad input can be dealt with by the default clause.

HTH

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