Author Topic: Passing a pointer to an array of an array  (Read 1504 times)

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Offline Munchor

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Passing a pointer to an array of an array
« on: October 22, 2011, 05:46:06 am »
I need some help with a pointer problem I'm facing. I have this:

Code: [Select]
int my_array[26][24]; /* An 2 dimensions array */

call_function(NEED_HELP_HERE);

call_function() requires an argument, an array. I need to pass my_array. However, I know that passing arrays in functions is memory consuming and not very clean. So, instead, I want to pass a pointer to the array.

So my question is how to declare the pointer to the array, how do I declare it?

Code: [Select]
void call_function(NEED_HELP_HERE)
{
  /* This function receives a pointer to an array as argument */
}

The question is what to put in "NEED_HELP_HERE" places. My issue is that I don't know what type the pointer to the array of arrays is.

Thanks in advance!

Offline thepenguin77

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Re: Passing a pointer to an array of an array
« Reply #1 on: October 22, 2011, 11:20:04 am »
That might work, but why not save all the hassle and do this?

Code: [Select]
int my_array[26][24] = {0};

call_function(my_array);

////////////////////////////////

void call_function(int array[26][24])
{
for (int iii = 0; iii<26; iii++)
{
for (int jjj = 0; jjj<24; jjj++)
{
array[iii][jjj] = iii*jjj;
}
}
}

When you just type the name of an array, like "my_array," that actually is the pointer to the array. You only dereference it when you start to use [].

Also, I would suggest that you use a 1 dimensional array. Two dimensional arrays are just handled like 1 dimensional arrays in memory anyways.
« Last Edit: October 22, 2011, 11:20:30 am by thepenguin77 »
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Offline Munchor

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Re: Passing a pointer to an array of an array
« Reply #2 on: October 22, 2011, 01:21:36 pm »
That might work, but why not save all the hassle and do this?

Code: [Select]
int my_array[26][24] = {0};

call_function(my_array);

////////////////////////////////

void call_function(int array[26][24])
{
  for (int iii = 0; iii<26; iii++)
  {
    for (int jjj = 0; jjj<24; jjj++)
    {
       array[iii][jjj] = iii*jjj;
    }
  }
}

When you just type the name of an array, like "my_array," that actually is the pointer to the array. You only dereference it when you start to use [].

Also, I would suggest that you use a 1 dimensional array. Two dimensional arrays are just handled like 1 dimensional arrays in memory anyways.


Oh ooops, I forgot arrays are just pointers, how silly of me, thanks for reminding me ;)