Reputation: 253

Returing an array

I am trying to add two matrices using the following code:

    #include <stdio.h>
    int matrix (void)
    {
        int a[2][2];
        int b[2][2];
        int c[2][2];
        int i, j;
        for (i = 0; i < 2; ++i) {
            for (j = 0; j < 2; ++j) {
                    scanf("%d", &a[i][j]);
            }
        }
        for (i = 0; i < 2; ++i) {
            for (j = 0; j < 2; ++j) {
                    scanf("%d", &b[i][j]);
            }
        }
        for (i = 0; i < 2; ++i) {
            for (j = 0; j < 2; ++j) {
                    c[i][j] = a[i][j] + b[i][j];
            }
        }
        return c;
    }
    int main ()
    {
        int i, j;
        int c[2][2];
        c = matrix();
        for (i = 0; i < 2; ++i) {
            for (j = 0; j < 2; ++j) {
                    printf("%d", c[i][j]);
            }
            printf("\n");
        }
        return 0;
    }

Above code is throwing many errors. Please explain why so many errors are shown by my compiler.

EDIT- I used GCC 4.4.3 when compiling above code.

EDIT2 - I got following errors and warnings when compiling above code.

test.c: In function ‘matrix’:
test.c:23: warning: return makes integer from pointer without a cast
test.c:23: warning: function returns address of local variable
test.c: In function ‘main’:
test.c:29: error: incompatible types when assigning to type ‘int[2][2]’ from type ‘int’

Upvotes: 1

Answers (5)

Fahad Naeem

Reputation: 535

Your're returning 2D-Array by using return c which can only be used to return a variable having data type other than 1D or 2D-Array. To fix this, you need to return 2D-Array i.e

return [i][j]

Also, you've declared c as 2D-Array but while returning you're using it as a variable.

int c[2][2];
c = matrix();

To fix it, either use

c[i][j]= matrix();

or declare c as

int c;

Upvotes: -1

ani627

Reputation: 6057

Try this fixed code:

#include <stdio.h>
void matrix (int c[][2]) //Fix 1
{
    int a[2][2];
    int b[2][2];
    int i, j;
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
                scanf("%d", &a[i][j]);
        }
    }
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
                scanf("%d", &b[i][j]);
        }
    }
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
                c[i][j] = a[i][j] + b[i][j];
        }
    }
}
int main ()
{
    int i, j;
    int c[2][2];
    matrix(c); //Fix 2
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
                printf("%d\t", c[i][j]); //Fix 3
        }
        printf("\n");
    }
    return 0;
}

Upvotes: 2

BLUEPIXY

Reputation: 40145

Fix as what you want.

#include <stdio.h>

int (*matrix(void))[2]{//return pointer as int (*)[2]
    static int c[2][2];//Can not be used to return the automatic local variables.
    int a[2][2];
    int b[2][2];
    int i, j;
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
                scanf("%d", &a[i][j]);
        }
    }
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
                scanf("%d", &b[i][j]);
        }
    }
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
                c[i][j] = a[i][j] + b[i][j];
        }
    }
    return c;
}
int main (){
    int i, j;
    int (*c)[2];
    c = matrix();
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 2; ++j) {
            printf("%d ", c[i][j]);//remove &
        }
        printf("\n");
    }
    return 0;
}

Upvotes: 2