Multidimensional arrays as parameters

[trifinite]

I have a multidimensional array called 'ticket', which has 25 rows and 6 columns. I want to parse this array to a function whose purpose is to initialize the array contents of ticket (for simplicity, let's assume all elements in the array are initialized to zero). Please note, I *must* use a separate function to achieve this initialization.

Below is the code I have, which is clearly wrong, but hopefully it makes it clear as to what I want to achieve. If someone could please correct my code or point me in the right direction it would be greatly appreciated.

Thank you.

int main(void)
{
    int ticket[25][6];
 
    /* ... */
 
    /* Fill array with zeros */
    init_ticket(ticket);
 
    /* ... */
}
 
void init_ticket(int ticket)
{
    int col;
    int row;
 
    for (row = 0; row < 25; row++)
    {
        for (col = 0; col < 6; col++)
        {
            ticket[row][col] = 0;
        }
    }
}

[vpawizard]

I have a multidimensional array called 'ticket', which has 25 rows and 6 columns. I want to parse this array to a function whose purpose is to initialize the array contents of ticket (for simplicity, let's assume all elements in the array are initialized to zero). Please note, I *must* use a separate function to achieve this initialization.

Below is the code I have, which is clearly wrong, but hopefully it makes it clear as to what I want to achieve. If someone could please correct my code or point me in the right direction it would be greatly appreciated.

Thank you.

int main(void)
{
    int ticket[25][6];
 
    /* ... */
 
    /* Fill array with zeros */
    init_ticket(ticket);
 
    /* ... */
}
 
void init_ticket(int ticket)
{
    int col;
    int row;
 
    for (row = 0; row < 25; row++)
    {
        for (col = 0; col < 6; col++)
        {
            ticket[row][col] = 0;
        }
    }
}

Hello,
The array 'ticket' is a two dimensional array. So, the data type of ticket is int[][] or int** and not int. So, the argument of init_ticket would be int [][] ticket or int** ticket. The function call is perfectly okay.

Regards,

[trifinite]

Thanks for your prompt reply.

Doing so results in the following compiler (gcc) warning:

gcc -g -Wall -ansi -pedantic -o rand rand.c
rand.c: In function 'main':
rand.c:43: warning: passing argument 1 of 'init_ticket' from incompatible pointer type


Code below:

int main(void)
{
    int ticket[25][6];
 
    /* ... */
 
    /* Fill array with zeros */
    init_ticket(ticket);
 
    /* ... */
}
 
void init_ticket(int** ticket)
{
    int col;
    int row;
 
    for (row = 0; row < 25; row++)
    {
        for (col = 0; col < 6; col++)
        {
            ticket[row][col] = 0;
        }
    }
}

[vpawizard]

This is because the ticket is an array and the procedure is expecting a double-pointer.

http://gcc.gnu.org/ml/gcc-bugs/2005-03/msg01391.html

You can declare the function as
void init_ticket(int[25][6]);

and the declarator line of definition as
void init_ticket(int ticket[25][6]);

Another point to note here is that only first dimension of array can be empty.

void init_ticket(int[][]); //Error
void init_ticket(int[][6]); //OK
void init_ticket(int[25][6]); //OK

The same rule applies for arrays with more dimensions.i.e.arr[][6][10]

Regards,

[trifinite]

Thanks again for your help; it seems to be working :-)

I have a question though that you might be able to clear up for me. I am interested to know why the array can be modified when parsed by value. I thought that it could only be modified if it were parsed by reference. My code is below.

I am currently reading a book on C (Practical C Programming, Oualline) and have not yet reached pointers/references. It has been a while since I last covered this material, so perhaps my memory is a little foggy.

#define GAMES       6
#define SELECTIONS 25
 
/* This is parsing by value, right? */
void create_ticket(int ticket[][SELECTIONS])
{
    int  game;
    int  selection;
 
    for (game = 0; game < GAMES; game++)
    {
        for (selection = 0; selection < SELECTIONS; selection++)
        {
            /* Initialize array elements to zero */
            ticket[game][selection] = 0;
 
            /* When I print the array's elements **OUTSIDE** of this function
             * it is evident that the values have been initialized correctly.
             * How can this be since I parsed the array by value???
             */
        }
    }
}