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problem with pointers

 
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cerr



Joined: 10 Feb 2011
Posts: 241
Location: Vancouver, BC

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problem with pointers
PostPosted: Thu Feb 17, 2011 1:14 pm     Reply with quote

Hi There,

I think I'm running into some kind of problems with my pointers... Surprised

I defined a
Code:
typedef struct {
  int16 value;
  char id;
} eevalues;

and then an array of these values like this:
Code:
eevalues store[VARNUM]

and I pass it to a function as a eevalues *data pointer but in the function i can't access the values anymore :( I only get 0s trying to access it like this:
Code:
data[0]->value
- how come? Evil or Very Mad
jacqueskleynhans



Joined: 10 Apr 2008
Posts: 109
Location: Cape Town, South Africa

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PostPosted: Thu Feb 17, 2011 2:43 pm     Reply with quote

These forums are valuable resources have a look around and also try searching for your problem elements.
http://www.ccsinfo.com/forum/viewtopic.php?t=44697&highlight=struct

This might not help but it contains some struct examples. Also I found a google search with maybe something like struct and pointer with CCS. usually narrows a search better than using ccs search.

Best of luck

Jacques
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bkamen



Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA

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Re: problem with pointers
PostPosted: Thu Feb 17, 2011 2:59 pm     Reply with quote

cerr wrote:
Hi There,

I think I'm running into some kind of problems with my pointers... Surprised

I defined a
Code:
typedef struct {
  int16 value;
  char id;
} eevalues;

and then an array of these values like this:
Code:
eevalues store[VARNUM]

and I pass it to a function as a eevalues *data pointer but in the function i can't access the values anymore :( I only get 0s trying to access it like this:
Code:
data[0]->value
- how come? Evil or Very Mad


Did you try data[0].value ??

I do this stuff all the time...

And if you look in the K&R C programming Lanuage , you'll see that your use of '->' is incorrect as -> is used when the pointed structure is a pointer... which you don't have up there.

Check page 128-131 of K&R's "The C Programming Language" for more verbose usage to help you along.

-Ben
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Dazed and confused? I don't think so. Just "plain lost" will do. :D
cerr



Joined: 10 Feb 2011
Posts: 241
Location: Vancouver, BC

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Re: problem with pointers
PostPosted: Thu Feb 17, 2011 5:03 pm     Reply with quote

bkamen wrote:

And if you look in the K&R C programming Lanuage , you'll see that your use of '->' is incorrect as -> is used when the pointed structure is a pointer... which you don't have up there.

Exactly right, -> is used to dereference (it's the same as (*XYZ)) and i had a brain fart there and didn't realize that. But why would the code compile at all? I would ixpect it to throw an error like value is not an element of data* or similar...
bkamen



Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA

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Re: problem with pointers
PostPosted: Thu Feb 17, 2011 5:04 pm     Reply with quote

cerr wrote:
bkamen wrote:

And if you look in the K&R C programming Lanuage , you'll see that your use of '->' is incorrect as -> is used when the pointed structure is a pointer... which you don't have up there.

Exactly right, -> is used to dereference (it's the same as (*XYZ)) and i had a brain fart there and didn't realize that. But why would the code compile at all? I would ixpect it to throw an error like value is not an element of data* or similar...


(shrug)

Cheers,

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D
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