Need help to avoid using a global array variable

Hi all, this is my first post :-) I am learning C++ and I would really appreciate your help.

I wrote a small program that generates random combinations of lottery numbers, and which can be adapted to different types of lotteries.

The problem I am trying to solve is that, as you can see, I have used an array as a global variable.

If this wasn't an array, I would know how to use either pointers or references to avoid a global variable. However, I am not sure how to do this with an array.

Many thanks in advance -- any help or input will be greatly appreciated!

Code:

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/* Generate combinations of lottery numbers */

#include <algorithm>        // for sort()
#include <conio.h>        // for getch()
#include <iostream>
#include <time.h>        // for time()

using namespace std;

int const HOW_MANY = 5;                        // set how many numbers are returned each time
int const CEILING = 90;                        // set the highest number that can be returned
int numbers[HOW_MANY] = {0};                // array containing the main numbers

int randomize(int max) {                // return a random number between 1 and max
        return rand() &#37; max + 1;
}

void doNumbers() {
        int i;
        for (i=0; i<HOW_MANY; i++)
                numbers[i] = randomize(CEILING);        // call randomize() HOW_MANY times to generate the combination
        sort(numbers, numbers+HOW_MANY);                // sort the combination
        for (i=0; i<(HOW_MANY-1); i++)
                if (numbers[i] == numbers[i+1])                // compare each number with the next one
                        doNumbers();                        // if there are any duplicates, repeat the function
}

void printNumbers() {
        int i;
        for (i=0; i<HOW_MANY; i++)
                cout << numbers[i] << "\t";
}

void giveOptions() {
        cout << "\n\nWould you like one more combination?\n\n";
        cout << "- Enter Y for YES\n";
        cout << "- Enter N to end the program" << "\n\n\n";
        int _getch();
        switch (_getch()) {
                case 'y':
                case 'Y':
                        doNumbers();
                        printNumbers();
                        giveOptions();
                        break;
                case 'n':
                case 'N':
                        return;
                default:
                        cout << "\n\nPlease enter either Y or N\n\n\n";
                        giveOptions();
        }
}

int main() {
        srand(unsigned(time(NULL)));
        doNumbers();
        printNumbers();
        giveOptions();
        return 0;
}

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The name of an array may be interpreted as a pointer to the first element of the array. Does that help?

Thanks Lindley,

I tried to use the array name as if it were a pointer, but I got all sorts of compiler errors. As you can see, the code not only assigns a value to each element of the array, but it also sorts the values, and checks for duplicates.

I am probably missing something obvious, but I am not sure of which exact syntax should be used in the function doNumbers() in case I were to create a local array instead than a global one.

I also tried creating an array on the free store:

Code:

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int *numbers = new int[5];

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...but then I didn't know how to refer to it from within another function: whatever syntax I use, I get an "undeclared identifier" compile-time error.

What am I missing?

So you want to know how to pass arrays to functions?

Code:

---

void f(int* numbers, size_t size)
{
    for(size_t i = 0; i < size; ++i)
    {
        std::cout << numbers[i] << std::endl;
    }
}

int main()
{
    const int QTY = 5;
    int numbers[QTY] = {10, 20, 30, 40, 50}; 
    f(numbers, QTY);

    return 0;
}

---

Quote:

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If this wasn't an array

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Does it have to be an array? A vector is a lot more convenient.

Quote:

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Originally Posted by random++

Thanks Lindley,

I tried to use the array name as if it were a pointer, but I got all sorts of compiler errors.

---

Such as? Show both the attempted code and the result.

Quote:

---

Originally Posted by Mybowlcut

So you want to know how to pass arrays to functions?

---

Thank you SO much! I finally know what I was missing -- I have fixed the code as per your suggestion and it works perfectly!

Code:

---

/* Generate combinations of lottery numbers */

#include <algorithm>        // for sort()
#include <conio.h>        // for getch()
#include <iostream>
#include <time.h>        // for time()

using namespace std;

int const SIZE = 5;                        // set how many numbers are returned each time
int const CEILING = 90;                        // set the highest number that can be returned

void doNumbers(int *numbers, int SIZE);
void printNumbers(int *numbers);
void giveOptions(int *numbers, int SIZE);

int main() {
        int numbers[SIZE] = {0};
        srand(unsigned(time(NULL)));
        doNumbers(numbers, SIZE);
        printNumbers(numbers);
        giveOptions(numbers, SIZE);
        return 0;
}

int randomize(int max) {                // return a random number between 1 and max
        return rand() % max + 1;
}

void doNumbers(int *numbers, int SIZE) {
        for (int i=0; i<SIZE; i++)
                numbers[i] = randomize(CEILING);        // call randomize() SIZE times to generate the combination
        sort(numbers, numbers+SIZE);                // sort the combination
        for (int i=0; i<(SIZE-1); i++)
                if (numbers[i] == numbers[i+1])                // compare each number with the next one
                        doNumbers(numbers, SIZE);                                        // if there are any duplicates, repeat the function
}

void printNumbers(int *numbers) {
        for (int i=0; i<SIZE; i++)
                cout << numbers[i] << "\t";
}

void giveOptions(int *numbers, int SIZE) {
        cout << "\n\nWould you like one more combination?\n\n";
        cout << "- Enter Y for YES\n";
        cout << "- Enter N to end the program" << "\n\n\n";
        int _getch();
        switch (_getch()) {
                case 'y':
                case 'Y':
                        doNumbers(numbers, SIZE);
                        printNumbers(numbers);
                        giveOptions(numbers, SIZE);
                        break;
                case 'n':
                case 'N':
                        return;
                default:
                        cout << "\n\nPlease enter either Y or N\n\n\n";
                        giveOptions(numbers, SIZE);
        }
}

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Quote:

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Originally Posted by Mybowlcut

Does it have to be an array? A vector is a lot more convenient.

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I know -- thanks. That's actually my next goal: to re-write the same program using vectors. After that, I'll try to re-write it using classes as well. This will help me learn :)

Thanks again!

Quote:

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Originally Posted by Lindley

Such as? Show both the attempted code and the result.

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The error was "undeclared identifier".

What I was doing wrong (I now realized) is that, after creating the array within one function, I was trying to use it in another function without passing it in as an argument. Newbie mistake :)

Thanks a lot for your help!