need to pass and return arrays, how?

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need to pass and return arrays, how?

 
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  #1
Jul 18th, 2006
I'm trying to return a struct array from two functions. I don't know what to say. Here is my code:

#include <iostream>
#include <iomanip>
using namespace std;

struct worker {
    int    idNumber;
    int    hoursWorked;
    double hourlyRate;
    double earned;
};

???  input();
???  calculateEarned(worker []);
void outputWorkers(worker []);
int  overtimeWorkers(worker []);

const double OVERTIME_RATE = 1.5;

int main() {

    outputWorkers(calculateEarned(input()));
    

    return 0;
    
}

??? input() {

    int a;
    cout << "Enter number of workers: ";
    cin >> a;
    cout << endl;
    static worker w[a]; // is this right??
    return w;

}

??? calculateEarned(worker w[]) {


    cout << "enter the ID numbers of the " << sizeof(w) << " workers: ";

    for(int i = 0; i < sizeof(w); i++)
        cin >> w[i].idNumber;
    
    cout << endl << "enter the hours worked for the " << sizeof(w) << " workers: ";
    
    for(int k = 0; k < sizeof(w); k++)
        cin >> w[k].hoursWorked;
    
    cout << endl << "enter the base pay for each of the " << sizeof(w) << " workers: ";
    
    for(int a = 0; a < sizeof(w); a++)
        cin >> w[a].hourlyRate;
    
    return w;
}

void outputWorkers(worker w[]) {

    cout << setw(10) << "worker" << setw(10) << "rate" << setw(10) << "hours" << setw(10) << "pay"
         << endl << endl;
    
    for(int i = 0; i < sizeof(w); i++) {
    
    if(w[i].hoursWorked > 40)
        w[i].earned = static_cast<double>(w[i].hoursWorked - 40) * w[i].hourlyRate * OVERTIME_RATE
                      + static_cast<double>(40) * w[i].hourlyRate;
    else
        w[i].earned = static_cast<double>(w[i].hoursWorked) * w[i].hourlyRate;
    
        cout << fixed << setprecision(2)
             << setw(10) << w[i].idNumber
             << setw(10) << w[i].hourlyRate
             << setw(10) << w[i].hoursWorked
             << setw(10) << w[i].earned
             << endl;
    }
}

int overtimeWorkers(worker w[]) {

    int count;    
    for(int i = 0; i < sizeof(w); i++)
        if(w[i].hoursWorked > 40)
            count = i + 1;
    
    return count;
}
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Re: need to pass and return arrays, how?

 
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  #2
Jul 18th, 2006
there are two ways to declare a one-dimentional array

(1)??? calculateEarned(worker array[]);

and
(2)??? calculateEarned(worker * array);

but there is only one way to declare the return value, using a pointer to the beginning of the array.
worker* calculateEarned(worker []);
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Re: need to pass and return arrays, how?

 
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  #3
Jul 18th, 2006
ok, thanks, i will work on it
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Re: need to pass and return arrays, how?

 
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  #4
Jul 18th, 2006
to simplify:
C++ Syntax (Toggle Plain Text) 
  1. worker* input() {
  2.  
  3.     int a;
  4.     cout << "Enter number of workers: ";
  5.     cin >> a;
  6.     cout << endl;
  7.     worker w[a]; // is this right??
  8.     return w;
  9.  
  10. }
  11.  
  12. and then, say: <span class="ad_notxt"><code class="inlinecode">nextCall(input());</code></span>
how does this work?

I'm getting "returning a local variable" errors, and "size of w[] is not constant," and other, more inscrutable errors.
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Re: need to pass and return arrays, how?

 
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  #5
Jul 18th, 2006
here are the errors of the following code..
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workerlist.cpp: In function ‘int main()’:
workerlist.cpp:24: error: ‘w’ was not declared in this scope
jess@linux:~/cpp/labs10+11/Lab#10$ g++ workerlist.cpp
workerlist.cpp: In function ‘int main()’:
workerlist.cpp:24: error: ‘w’ was not declared in this scope
workerlist.cpp: In function ‘void input()’:
workerlist.cpp:39: error: storage size of ‘w’ isn't constant
C++ Syntax (Toggle Plain Text) 
  1. #include <iostream>
  2. #include <iomanip>
  3. using namespace std;
  4.  
  5. struct worker {
  6.     int    idNumber;
  7.     int    hoursWorked;
  8.     double hourlyRate;
  9.     double earned;
  10. };
  11.  
  12. void input();
  13. void  calculateEarned(worker []);
  14. void outputWorkers(worker []);
  15. int  overtimeWorkers(worker []);
  16.  
  17. const double OVERTIME_RATE = 1.5;
  18.  
  19. int main() {
  20.  
  21.     input();
  22.     calculateEarned(w);
  23.     outputWorkers(w);
  24.     cout << overtimeWorkers(w) << " workers with overtime hours" << endl;
  25.  
  26.  
  27.     return 0;
  28.  
  29. }
  30.  
  31. void input() {
  32.  
  33.     int a;
  34.     cout << "Enter number of workers: ";
  35.     cin >> a;
  36.     cout << endl;
  37.     static worker w[a]; // is this right??
  38.  
  39. }
  40.  
  41. void calculateEarned(worker w[]) {
  42.  
  43.  
  44.     cout << "enter the ID numbers of the " << sizeof(w) << " workers: ";
  45.  
  46.     for(int i = 0; i < sizeof(w); i++)
  47.         cin >> w[i].idNumber;
  48.  
  49.     cout << endl << "enter the hours worked for the " << sizeof(w) << " workers: ";
  50.  
  51.     for(int k = 0; k < sizeof(w); k++)
  52.         cin >> w[k].hoursWorked;
  53.  
  54.     cout << endl << "enter the base pay for each of the " << sizeof(w) << " workers: ";
  55.  
  56.     for(int a = 0; a < sizeof(w); a++)
  57.         cin >> w[a].hourlyRate;
  58.  
  59. }
  60.  
  61. void outputWorkers(worker w[]) {
  62.  
  63.     cout << setw(10) << "worker" << setw(10) << "rate" << setw(10) << "hours" << setw(10) << "pay"
  64.          << endl << endl;
  65.  
  66.     for(int i = 0; i < sizeof(w); i++) {
  67.  
  68.     if(w[i].hoursWorked > 40)
  69.         w[i].earned = static_cast<double>(w[i].hoursWorked - 40) * w[i].hourlyRate * OVERTIME_RATE
  70.                       + static_cast<double>(40) * w[i].hourlyRate;
  71.     else
  72.         w[i].earned = static_cast<double>(w[i].hoursWorked) * w[i].hourlyRate;
  73.  
  74.         cout << fixed << setprecision(2)
  75.              << setw(10) << w[i].idNumber
  76.              << setw(10) << w[i].hourlyRate
  77.              << setw(10) << w[i].hoursWorked
  78.              << setw(10) << w[i].earned
  79.              << endl;
  80.     }
  81. }
  82.  
  83. int overtimeWorkers(worker w[]) {
  84.  
  85.     int count;    
  86.     for(int i = 0; i < sizeof(w); i++)
  87.         if(w[i].hoursWorked > 40)
  88.             count = i + 1;
  89.  
  90.     return count;
  91. }
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Re: need to pass and return arrays, how?

 
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  #6
Jul 18th, 2006
Error Returning a local variable

You are gettin this error since you are trying to return worker type array "w" which is local to the function and hence is destroyed when the function exits. Said simply the scope or the effect of the local variable is in the function itself since its memory is allocated in the stack of local variables which is destroyed when the function exits.

Errror size of w[] not constant

In C or C++ u cant declare an array like this i.e. an array whose size the compiler has to calculate at run time. C expects that you explicitly declare the size of the array during compile time.

Hence the acceptable options are

worker w [10];

OR

const int numberOfItems = 10;
worker w [numberOfItems];

Bye.
Last edited by ~s.o.s~; Jul 18th, 2006 at 4:38 pm.
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Re: need to pass and return arrays, how?

 
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  #7
Jul 18th, 2006
alright.. i had to rearrange all the functions to accommodate that fact, but it's done now. forget about returning pointers, for now..
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