array of pointers to strings

mirizar · #1 20-Jan-2005, 15:08

Hi!

I have an array of pointers to strings (char *name[maxnum]). I add elements to the array and output each element right after to check their content and it is okay.
char[counter] = value;
cout << char[counter] << endl;

However, at a later point in the code I output all the elements, and they are all equal to element the last element (maxnum). :-(

for (int i=0;i<=maxnum;i++) {
cout << char[i] << endl;
}

I do a similar process with an array of doubles (double [maxnum]) and the process above works fine.

Note that I do not want to use strings.
Can you help figure out what is wrong when I use the array of pointers to store strings?

Thanks, Michelle

davekw7x · #2 20-Jan-2005, 16:44

Quote:

Originally Posted by mirizar

Hi!

I have an array of pointers to strings (char *name[maxnum]).
.
.
.
Can you help figure out what is wrong when I use the array of pointers to store strings?

Thanks, Michelle

Here's the drill: Instead of telling us what you did (or what you think you did, or what you tried to do), show us what you did (post the code).

Tell us:

1. What you expected to get.
2. What you got and don't understand.
3. What compiler? What operating system? (Sometimes it matters.)

Regards,

Dave

mirizar · #3 20-Jan-2005, 19:42

Quote:

Originally Posted by davekw7x

Here's the drill: Instead of telling us what you did (or what you think you did, or what you tried to do), show us what you did (post the code).

Tell us:

1. What you expected to get.
2. What you got and don't understand.
3. What compiler? What operating system? (Sometimes it matters.)

Regards,

Dave

Hi Dave!

My code is below:

CPP / C++ / C Code:

// Homework1.cpp : Exercise 2.56:  Program to compute weekly payroll
// for a company
// Written by:  Michelle M. Irizarry-Ortiz
//

#include <iostream>

#include <iomanip>

using namespace std;

// Function declaration
void eatline();

// Global variables
char mainMenuSelection = ' ';
char employeeName[40];
char employeeType;

int main()
{

   // Constant declarations
   const int maxEmployees = 100;
   const double hrThreshold = 40.0, wklyCommSalary = 250.,
                     overTimeRatio=1.5, wklySalesPerc=5.7;
	             
						
   // Variable declarations
   int numberItems, val_employee_counter=0;
   double wklyPay = -1.,
             fixedWklySalary, 
	hourlyWage, hoursWorked, 
	grossWklySales, 
	ratePerItem,
             validwklyPay[maxEmployees];
   char *validEmployeeName[maxEmployees];
  
   
   // While user does not want to quit program
   while (mainMenuSelection != 'Q' && mainMenuSelection !='q') {
        
      // Display main menu
      cout << "\n";
      cout << "**************************************\n";
      cout << "***** WELCOME TO PAYROLL PROGRAM *****\n";
      cout << "*                                    *\n";
      cout << "* E - Enter employee information     *\n";
      cout << "* P - Print report                   *\n";
      cout << "* C - Clear database                 *\n";
      cout << "* Q - Quit program                   *\n";
      cout << "* (To quit a module, enter '!'       *\n";
      cout << "*  at any time)                      *\n";
      cout << "*                                    *\n";
      cout << "**************************************\n\n";
      cout << " Enter letter from above menu: ";

      // Get menu selection from user
      if (cin.peek() == '!') {eatline(); break;}
      cin >> mainMenuSelection; 
      eatline(); // To empty input stream in case
                   // more than one character is entered
                   
      // If user wants to enter employee info
      if (mainMenuSelection == 'E' || mainMenuSelection == 'e') {

         while (wklyPay < 0) {
            
            // Display employee info form
            cout << "\n";
            cout << "**************************************\n";
            cout << "*****     EMPLOYEE INFO FORM     *****\n";
            cout << "**************************************\n";
            cout << " Enter employee name: " << endl;
            //Get employee name
            if (cin.peek() == '!') {eatline(); break;}
            cin.get(employeeName,40,'\n'); // To be able to enter whitespace
            eatline();
            cout << "\n Employee types:\n";
            cout << "  1 - Manager\n";
            cout << "  2 - Hourly worker\n"; 
            cout << "  3 - Commission worker \n";
            cout << "  4 - Piece worker\n";
            cout << " Enter employee type (1-4):  ";
            // Get employee type
            if (cin.peek() == '!') {eatline(); break;}
            cin >> employeeType; //Note:  Need to flush input stream so ok if more than one character is entered
            eatline(); // To empty input stream in case
	       	// more than one character is entered
    	cout << "\n";
    
	// Enter additional employee information
	// depending on type
           	// Change output precision for dealing with currency
	cout << fixed << setprecision(2);

	switch (employeeType) {

	   case '1': // manager
	   cout << " Enter fixed weekly salary:  ";
                if (cin.peek() == '!') {eatline(); break;}
	   cin >> fixedWklySalary;
	   wklyPay = fixedWklySalary;
	   break;

				   
	   case '2': // hourly worker
	   cout << " Enter hourly wage:  ";
                if (cin.peek() == '!') {eatline(); break;}
	   cin >> hourlyWage;
	   cout << " Enter hours worked:  ";
                if (cin.peek() == '!') {eatline(); break;}
	   cin >> hoursWorked;
                if (hoursWorked <= hrThreshold) {
	      wklyPay = hourlyWage * hoursWorked;
	   }
	   else {
	       wklyPay = hourlyWage * (hrThreshold
		        + 1.5 * (hoursWorked-hrThreshold));
	   }

	   break;

	   case '3': // commision worker
	   cout << " Enter gross weekly sales:  ";
                if (cin.peek() == '!') {eatline(); break;}
	   cin >> grossWklySales;
	   wklyPay = wklyCommSalary + grossWklySales * wklySalesPerc / 100;          
                break;


	   case '4': // piece worker
	   cout << " Enter items produced:  ";
                if (cin.peek() == '!') {eatline(); break;}
	   cin >> numberItems;
	   cout << " Enter rate per item:  ";
                if (cin.peek() == '!') {eatline(); break;}
	   cin >> ratePerItem;
	   wklyPay = numberItems * ratePerItem;
	   break;

	   default: // default
	   cout << "Incorrect employee type entered.\n";
	   cout << "Try again!\n";
	   break; // Need to go back to enter employee info if something is wrong
	} // end switch

	// Store valid data into arrays for summary report
	if (wklyPay >= 0.) {
	   cout << "\nPay for employee " << employeeName << ":  $" << wklyPay << endl;	
	   validwklyPay[val_employee_counter] = wklyPay;
                validEmployeeName[val_employee_counter] = new char[40];
	   validEmployeeName[val_employee_counter] = employeeName;
                cout << "here" << val_employee_counter << validEmployeeName[val_employee_counter] << endl;
                for (int i=0;i<=(val_employee_counter);i++) {
                   cout << "here2!!! " << validwklyPay[i] << "  " << &validEmployeeName[i] << endl;
                }
	   val_employee_counter++;
	} // end if

          } // end while				
			
          wklyPay = -1.; // Restore weekly pay to -1
          cout << validEmployeeName[0] << endl;

       } // end if

      else if (mainMenuSelection == 'P' || mainMenuSelection == 'p') {

         if (val_employee_counter >= 1) { //Issue:  If second employeename is too long, first will be sub by it
            cout << endl << endl;
            cout << setw(40) << left << "   Employee Name" << setw(15) << right << "  Pay  " << endl;
            cout << setw(40) << left << "   *************" << setw(15) << right << "*******" << endl;
            for (int i=0; i<=(val_employee_counter-1); i++) {
                cout << i+1 << ". " << setw(40) << left << validEmployeeName[i] << "$" << setw(14) << right << validwklyPay[i] << endl;
            }
            cout << endl << endl;
         } // end if
         
         else {
            cout << "\nNo employee information has been entered!\n";
         } // end else

      } // end else if
        
     else if (mainMenuSelection == 'C' || mainMenuSelection == 'c') {
        val_employee_counter = 0;
     } // end else if

  } // end while


   return 0;
}


// Function to eat remainder of line
void eatline()
{
   while(cin.get() != '\n') continue;

}

The statements/blocks in question are:

char *validEmployeeName[maxEmployees];

validEmployeeName[val_employee_counter] = employeeName;

for (int i=0; i<=(val_employee_counter-1); i++) {
cout << i+1 << ". " << setw(40) << left << validEmployeeName[i] << "$" << setw(14) << right << validwklyPay[i] << endl;
}

Thanks! Michelle

davekw7x · #4 20-Jan-2005, 20:22

Quote:

Originally Posted by mirizar

Hi Dave!

My code is below:

The statements/blocks in question are:

char *validEmployeeName[maxEmployees];

validEmployeeName[val_employee_counter] = employeeName;

for (int i=0; i<=(val_employee_counter-1); i++) {
cout << i+1 << ". " << setw(40) << left << validEmployeeName[i] << "$" << setw(14) << right << validwklyPay[i] << endl;
}

Thanks! Michelle

You are using arrays of char. You want to use strcpy() to copy the names:

Your program does this:

CPP / C++ / C Code:

   validEmployeeName[val_employee_counter] = employeeName;

This makes the pointer point to the employeName array, whose content changes for each entry, and finally it contains the last employee name that was entered. In other words, all of your validEmployeeName[] pointers end up pointing to the employeeName array, therefore the output will show them to be the same.

To get the name into the pointer array element that you just obtained from new, use strcpy.

CPP / C++ / C Code:

// at the top of the file: use this header for strcpy()
#include <cstring>

//
// Instead of your statement use this:
   strcpy(validEmployeeName[val_employee_counter], employeeName);

//

(Also setting validEmployeeName[...] equal to something other than the value given by new means that the memory can never be freed. This is a Bad Thing. It is the programmer's responsibility to make sure that for every memory block obtained by new it is returned to the operating system by a delete before exiting. This is important!)

Regards,

Dave

mirizar · #5 21-Jan-2005, 10:17

Hi! Thanks! This worked. Now it makes sense!
My only question is: how do I use delete to free up the memory for every pointer in the array?

Within the 'C' option, I tried a single: delete [] validEmployeeName;

but it did not work. :-(

Do I need a loop?

Thanks, Michelle

mirizar · #6 21-Jan-2005, 10:24

Ok! Got it:
for (int ctr=0; ctr<=(val_employee_counter - 1); ctr++){
delete [] validEmployeeName[ctr];
}

Finally getting the hang of it

Michelle

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