Why aren't my pointers to integer arrays working?

Question

Here is the problem: http://cps125.scs.ryerson.ca/labs/homework8.gif

Here is my attempt:

#include <stdio.h>

void tenfold(int (*array1)[9], int (*array2)[9])
{
    int i;
    for (i = 0; i < 9; i++) {
        if ((*array1)[i] > 0) {
            (*array2)[i] = 10 * (*array1)[i];
        } else {
            (*array2)[i] = (*array1)[i];
        }
    }
}

int main()
{
    int array1[9] = { 3, 4, 5, 6, 7, -8, -9, 1, 2 }, array2[9], i;

    tenfold(&array1, &array2);

    for (i=0; i < 9; i++) {
        printf("%lf ", array2[i]);
    }
    return 0;
}

Here is the output:

44100667367791664000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000.000000 441006673677917200000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000.000000 4410066736779177 60000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000.000000 4410066736779183200000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000.000000 44100667367791888000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000.000000 44100691391845304000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000.000000 441006913918452980000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000.000000 4410066736779155 20000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000.000000 4410066736779160800000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000.000000

cmc · Accepted Answer · 2013-04-01T21:00:11.260

4

There is at least a problem here:

printf("%lf ", array2[i]);

%lf literally means "long float", however you want to print integers:

printf("%i\n", array2[i]);

Also remember that printf waits for \n to flush.

EDIT: As newacct pointed out, %f and %lf are both double in the end, since varargs promote float to double.

edited Apr 01 '13 at 21:00

answered Apr 01 '13 at 17:33

cmc

2,061
1
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18

1

@user1251385 always compiler with `-Wall` option – Grijesh Chauhan Apr 01 '13 at 17:37
1

As said above, compiling with `-W -Wall -Werror` will prevent this kind of mistakes from happening. Reading the man too! – cmc Apr 01 '13 at 17:40
and in `printf`, `%lf` is the same as `%f` (both are `double`) – newacct Apr 01 '13 at 20:26

MOHAMED · Answer 2 · 2013-04-02T17:03:30.810

No need to add asterisk in the definition of input array in the function tenfold

just define it as following

void tenfold(int array1[9], int array2[9])

And remove the asterisk * when using array1 and array2 into the function tenfold

void tenfold(int array1[9], int array2[9])
{
    int i;
    for (i = 0; i < 9; i++) {
        if ((array1)[i] > 0) {
            (array2)[i] = 10 * (array1)[i];
        } else {
            (array2)[i] = (array1)[i];
        }
    }
}

and when you call the tenfold function in the main:

tenfold(array1, array2);

score 0 · Answer 3 · answered Apr 01 '13 at 17:35

0

"%lf " is the format for a float, not an int.

answered Apr 01 '13 at 17:35

stark

12,615
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50

Why aren't my pointers to integer arrays working?

3 Answers3

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