Thread: clearing array

hi all

i have a question. if i have and array and have already initialize it as follow

Code:

unsigned char data[5] = {0};

how do i clear it after i have used it?

lets say

Code:

for (int a= 0; a<5;a++)
  data[a] = a;   //filling array with data

//after filling it i want to clear the whole array

data[X] = 0:  //is this the right way.What to put for X to clear the whole array?

Thanks

When you declare an array on the stack, as you have in your original post, you do not have to worry too much about memory management. Your array was declared in the scope of a function, say main(). If there is room on the stack (usually yes) the array will be created and ready to use. When main() returns, the character array is out of scope and automatically deleted.

If you want to re-use the character array, don't try clear it, just overwrite it.

Code:

data[X] = {0};

Pull my finger

By clearing you mean you want to zero the contents?
You can use a loop just like you did above,

Code:

for (a = 0; a < 5; a++)
    data[a] = 0;

Or you can use the memset function

Code:

#include <string.h>

memset(data, 0, 5);

(edit: oh no too late)

Originally Posted by quzah

No. That only "clears" one element. That initializer only works at the time of declaration. Otherwise you have to use a loop, or memset, which is just a loop wrapped in a function.


Quzah.

Ughhhh... I keep forgetting initialization and assignments are two different beasts in c. Oh sweet lord, I think I'm having flashbacks of LISP. Ooohhhhh.... my aching hips.

Originally Posted by quzah

No. That only "clears" one element. That initializer only works at the time of declaration. Otherwise you have to use a loop, or memset, which is just a loop wrapped in a function.


Quzah.

quick question: is it wrong to do something like:

Code:

data[0] = '/0';

i know it doesn't _clear_ the elements, but if you are just going to overwrite them anyway would this be bad form?

thanks.

Originally Posted by citizen

It doesn't have to be more complicated than

Code:

 bigstr[80] = "I like rainbows, and puppies, and sunny days!";

Actually it does have to be more complicated than that. Your code doesn't rewrite the array filling it with a string. It tries to assign the index bigstr[80] with a string. Obviously this will fail. You can only fill a char array with a string like that when it is being declared.

Code:

char bigstr[80] = "I like rainbows, and puppies, and sunny days!";

To overwrite the array with a new string, you need to use a function like strcpy().

I see I see...thanks guy

If you just to clear the array why can't you just reinitialise it to zero?

Code:

anarray[5]={0,0,0,0,0};

Originally Posted by hammer1234

If you just to clear the array why can't you just reinitialise it to zero?

Code:

anarray[5]={0,0,0,0,0};

You can't reinitialise it. Reinitialise... kind of an oxymoron isn't it?

Mr hammer1234 just tell me what will you do if the array size if 100 ?

why not use the loop instead of writing each value ?


REALNAPSTER

Originally Posted by realnapster

Mr hammer1234 just tell me what will you do if the array size if 100 ?

why not use the loop instead of writing each value ?


REALNAPSTER

Because Mr realnapster the person posting the code said the array has a size of 5.