Compilation problems ( apparently )

[guro]

#include <stdio.h>
#define SIZE 3

/* function prototype */
void swaparrays( int*, int* );
void printarray( int* );

int main( int argc, char *argv[] ) {
    printf( "[!] Program swaps the elements of\
     two integer arrays\n" );
    int s1[SIZE][SIZE] = {  { 1, 3, 4 },
                            { 5, 1, 2 },
                            { 7, 6, 9 } };

    int s2[SIZE][SIZE] = {  { 3, 2, 1 },
                            { 5, 2, 8 },
                            { 0, 1, 3 } };
    printf( "Array 1:\n" );
    printarray( s1[SIZE] );
    printf( "Array 2:\n" );
    printarray( s2[SIZE] );

    /* swap arrays */
    swaparrays( s1[SIZE], s2[SIZE] );

    printf( "Now...\n" );
    printf( "Array 1:\n" );
    printarray( s1[SIZE] );
    printf( "Array 2:\n" );
    printarray( s2[SIZE] );

    /* exit normally */
    return 0;

} // END main

/*
 * Function: swaparrays.
 *      This Function actually swaps the elements
 *  of the two integer 3x3 arrays.
 * Arguments: takes two pointers of integers.
 * Returns: nothing (void) .
 */
void swaparrays( int* a, int* b ) {
    int i;
    int j;
    int temp;

    for( i = 0; i < SIZE; i++ ) {
        for( j = 0; j < SIZE; j++ ) {
            temp = a[i][j];
            a[i][j] = b[i][j];
            b[i][j] = temp;
        } // END INNER FOR LOOP
    } // END OUTER FOR LOOP
} // END swaparrays

/*
 * Function: printarray.
 *      This function prints a 3x3 integer array.
 * Arguments: takes in a pointer to an integer array.
 * Returns: nothing (void) .
 */
 void printarray( int *a ) {
     int i;
     int j;

     for( i = 0; i < SIZE; i++ ) {
         for( j = 0; j < SIZE; j++ ) {
             if( j % SIZE == 0)
                putchar( '\n' );
             printf( "%d %d %d", a[i][j] );
         } // END INNER FOR LOOP
     } // END OUTER FOR LOOP
     putchar( '\n' );
 } // END printarray

when try to compile with gcc it outputs:

pointers3.c: In function 'swaparrays':
pointers3.c:51: error: subscripted value is neither array nor pointer
pointers3.c:52: error: subscripted value is neither array nor pointer
pointers3.c:52: error: subscripted value is neither array nor pointer
pointers3.c:53: error: subscripted value is neither array nor pointer
pointers3.c: In function 'printarray':
pointers3.c:72: error: subscripted value is neither array nor pointer

I know something i miss with multidimensional arrays. I would like to keep this structure in my program regarding the algorithms but also i want to compile the program correctly. Any ideas?

[quzah]

You can't index a single pointer as if it were a two dimension array. Not without doing the math yourself:

x = ptr[ MAXCOLS * row + col ];

Quzah.

[guro]

Thanks for the reply. I tried to fix the code, but really the best thing i did, was to print some addresses. The problem i have to solve is the following:
Write a program that contains a function with prototype
a. void swaparrays(int*, int*); This swaps the values of two 3x3
arrays. Initialize the values of the arrays with any numbers you want.
As far as i understand that's is not easy task if the prototype of the function takes as arguments of type *int. If it was something like swaparrays( int*[SIZE], int*[SIZE] ), then i would have better chances. So my question is: Do i misanderstood the problem, or it is not solveable with these specific conditions the exercise has?

[zalezog]

void swaparrays(int*, int*);

If you are going against the specifications, the method prototype could be

void swaparrays(int**, int**);

And your matrix is 2 dimensional.

int s1[SIZE][SIZE]

But function expects a 1-Dimensional array, one thing you can do is

void swaparrays( int* a, int* b ) {
    int i;
    
    int temp;

    for( i = 0; i < SIZE; i++ ) {
           /*Normal swap*/
            temp = a[i];
            a[i] = b[i];
            b[i] = temp;
        
    } 
} // END swaparrays

And call the function in main as

 for (i = 0; i < SIZE; i++)
       swaparrays( s1[i], s2[i] );

and the print array method as

void printarray( int *a ) {
     int i;
     putchar( '\n' );
     for( i = 0; i < SIZE; i++ ) {
         printf( "%d ", a[i] );
         
     } 
     putchar( '\n' );
 } // END pr

and in main() call your method as

for (i = 0; i < SIZE; i++)
       printarray( s1[i] );

This can be done with single dimensional arrays too.(although function calls and methods would be much more simpler)l

Sample Run

Array 1:

1 3 4

5 1 2

7 6 9
Array 2:

3 2 1

5 2 8

0 1 3
Now...
Array 1:

3 2 1

5 2 8

0 1 3
Array 2:

1 3 4

5 1 2

7 6 9

[guro]

Wow !! Really you gave me the point i missed. Thanks very much for your reply. It puts the things in order in my head. Thanks again!
Now regarding the printarray( int *a) function you gave me, when the array is 2x2 ( test it ), maybe and for 3x3 and so on so forth it doesn't work for me. But that's not a problem because the printarray function can be written without any specifications given by the exercise. So i completed the program which is the following:

// credits: zalezog for swaparrays functions and not only!
#include <stdio.h>
#define SIZE 2

void swaparrays( int *a, int *b ) {
	int i;
	int temp[SIZE];	// array of pointers

	for( i = 0; i < SIZE; i++ ) {
		temp[i] = a[i];
		a[i] = b[i];
		b[i] = temp[i];
	} // END FOR LOOP
	
} // END swaparrays

void printArray( int a[][SIZE] ) {
        int i;
        int j;

        for( i = 0; i < SIZE; i++ ) {
                for( j = 0; j < SIZE; j++ ) {
                        if( j % SIZE == 0 )
                                putchar( '\n' );
                        printf( "%3d", a[i][j] );
                } // END FOR LOOP
        } // END FOR LOOP
        putchar( '\n' );
} // END printArray

int main() {
	int i;

	int s1[SIZE][SIZE] = { {2, 3}, {6, 8} };
	int s2[SIZE][SIZE] = { {-2, -3}, {-5, -6} };

	printArray( s1 );
	printArray( s2 );
	
	for( i = 0; i < SIZE; i++ ) {
		swaparrays( s1[i], s2[i] );
	} // END FOR LOOP

	printArray( s1 );
	printArray( s2 );

	return( 0 );

} // END main

[zalezog]

Now regarding the printarray( int *a) function you gave me, when the array is 2x2 ( test it ), maybe and for 3x3 and so on so forth it doesn't work for me.

As long as your matrix is square of size SIZE * SIZE, it should work.

Here's my version:

#include <stdio.h>
#define SIZE 3

/* function prototype */
void swaparrays( int*, int* );
void printarray( int* );

int main( int argc, char *argv[] ) {
    int i = 0;
    //printf( "[!] Program swaps the elements of\
     //two integer arrays\n" );
    int s1[SIZE][SIZE] = {  { 1, 3, 4 },
                            { 5, 1, 2 },
                            { 7, 6, 9 } };

    int s2[SIZE][SIZE] = {  { 3, 2, 1 },
                            { 5, 2, 8 },
                            { 0, 1, 3 } };
    printf( "Array 1:\n" );
    for (i = 0; i < SIZE; i++)
       printarray( s1[i] );
    printf( "Array 2:\n" );
    for (i = 0; i < SIZE; i++)
        printarray( s2[i] );

    /* swap arrays */
    for (i = 0; i < SIZE; i++)
       swaparrays( s1[i], s2[i] );

    printf( "Now...\n" );
    printf( "Array 1:\n" );
    for (i = 0; i < SIZE; i++)
       printarray( s1[i] );

    printf( "Array 2:\n" );
    for (i = 0; i < SIZE; i++)
       printarray( s2[i] );


    /* exit normally */
    return 0;

} // END main

/*
 * Function: swaparrays.
 *      This Function actually swaps the elements
 *  of the two integer 3x3 arrays.
 * Arguments: takes two pointers of integers.
 * Returns: nothing (void) .
 */
void swaparrays( int* a, int* b ) {
    int i;
    int j;
    int temp;

    for( i = 0; i < SIZE; i++ ) {

            temp = a[i];
            a[i] = b[i];
            b[i] = temp;
         // END INNER FOR LOOP
    } // END OUTER FOR LOOP
} // END swaparrays

/*
 * Function: printarray.
 *      This function prints a 3x3 integer array.
 * Arguments: takes in a pointer to an integer array.
 * Returns: nothing (void) .
 */
 void printarray( int *a ) {
     int i;
     int j;
     putchar( '\n' );
     for( i = 0; i < SIZE; i++ ) {
         printf( "%d ", a[i] );
          // END INNER FOR LOOP
     } // END OUTER FOR LOOP
     putchar( '\n' );
 } // END printarray