Re: Array of arrays

[Tristan Van Berkom]

On Sat, Feb 27, 2010 at 9:50 PM, Brian Lavender <br...@brie.com> wrote:
> I guess the list stripped the attachments. The code is included in this
> message.
>

Hi,
    First of all it would be helpful if you told us what is the problem with
your code, off the bat I could tell you that the way you pass a pointer
to an array of pointers is foreign to me, I think I would have just used
"GArray ***arrays_p;" for that argument.

But on the other hand, you could just save yourself that headache and
use a GPtrArray of GArrays (you could even get carried away and whip
up an api that updates the values of ptrarray->pdata[i] = garray->data
and have a real indexable array in C...).

Cheers,
          -Tristan

> brian
>
> On Sat, Feb 27, 2010 at 06:47:30PM -0800, Brian Lavender wrote:
>> I was experimenting with creating an array of arrays. Maybe I shouldn't
>> be using GArray but something different such as pointer arrays and
>> allocating memory for each element?
>>
>> I wrote two sample programs. The first one, just loads one array. The
>> second, loads an array of arrays. I don't know if I have a problem with
>> operator precedence or if the GArrays point to just one array.
>>
>> The two programs are the following.
>>
>> simplearray.c - loads just one array
>> simplearray2.c - loads an array of arrays
>>
>> Any input is appreciated.
>
> === simplearray.c ===
>
> #include <glib.h>
>
> #define NUM_ARYS 5
>
> void load_array( GArray **garray)
> {
>  gint i, storevalue;
>  *garray = g_array_new (FALSE, FALSE, sizeof (gint));
>  for (i = 0; i < 10; i++) {
>    storevalue = (i + 103) % 45;
>    g_array_append_val (*garray, storevalue);
>  }
> }
>
> int main() {
>  GArray *garray[NUM_ARYS];
>  gint i, storevalue;
>  /* We create a new array to store gint values.
>     We don't want it zero-terminated or cleared to 0's. */
>  load_array(&garray[0]);
>
>  for (i = 0; i < 10; i++)
>      g_print ("index %d value %d\n",
>               i, g_array_index (garray[0], gint, i));
>  g_array_free (garray[0], TRUE);
> }
>
> === simplearray2.c ===
>
>
> #include <glib.h>
>
> #define NUM_ARYS 5
>
> void load_array( GArray *(*garray)[NUM_ARYS] )
> {
>  gint i,j, storevalue;
>  for (j=0; j < NUM_ARYS; j++) {
>    (*garray)[j] = g_array_new (FALSE, FALSE, sizeof (gint));
>    g_printf("Load Array %d\n", j);
>    for (i = 0; i < 10; i++) {
>      storevalue = (i + 103) % ( (j +1) * 2 );
>      g_array_append_val ( (*garray)[j], storevalue );
>      g_print ("load idx %d value %d\n",
>               i, storevalue );
>    }
>  }
> }
>
> int main() {
>  GArray *garray[NUM_ARYS];
>  gint i,j, storevalue;
>  /* We create a new array to store gint values.
>     We don't want it zero-terminated or cleared to 0's. */
>  load_array(&garray);
>
>  for (j=0; j < NUM_ARYS; j++) {
>    g_printf("Array %d\n", j);
>    for (i = 0; i < 10; i++)
>      g_print ("index %d value %d\n",
>               i, g_array_index (garray[1], gint, i));
>  }
>
>  for (j=0; j < NUM_ARYS; j++)
>    g_array_free (garray[j], TRUE);
>
> }
>
> --
> Brian Lavender
> http://www.brie.com/brian/
>
> "About 3 million computers get sold every year in China, but people don't
> pay for the software. Someday they will, though. As long as they are going
> to steal it, we want them to steal ours. They'll get sort of addicted, and
> then we'll somehow figure out how to collect sometime in the next decade."
>
> -- Bill Gates (Microsoft) 1998
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