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Heartless
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 Posted: Sat Aug 16, 2008 2:36 pm Post subject: [C++] Explain something to me |
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What is this?
| Code: | int x = 10;
int *px = &x;
int **ppx; //<- What the hell is that? |
It looks like some kind of pointer, but it has 2 '*'s... And one more thing.
| Code: | Class S{
private:
int x;
public:
S(int temp) : x(temp) {} //<-- What is this also?
}; |
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oib111
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| Posted: Sat Aug 16, 2008 2:53 pm Post subject: |
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** means pointer to a pointer. As for the other one, it is a constructor. It is initializing x to whatever value was passed into temp. So if I said:
x would now equal 10.
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pkedpker
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| Posted: Sat Aug 16, 2008 3:09 pm Post subject: |
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** is pointer to a pointer which is used mostly for arrays.
** is two dimensional.
since lets say the first * points to 5 int's
the second star would point to 5x5 = 25.
I'd stay away from lvl 2 pointers they could mess with your head.. you gotta then be thinking everything in the first pointer like every int.. has another pointer pointing to it so it doubles on it self.
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Heartless
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lurc
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| Posted: Sat Aug 16, 2008 8:24 pm Post subject: |
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An example of using ** in a way would be like this:
TCHAR *tszStrings[10];
Thats a pointer to 10 strings.
TCHAR tszStrings[10][10];
Thats a pointer to 10 strings, all with 10 characters of space.
Even when you see
int main( int argc, char *argv[] )
argv is a pointer to a array of characters.
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Anden100
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nog_lorp
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| Posted: Sun Aug 17, 2008 2:53 am Post subject: |
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| HornyAZNBoy wrote: | | int **pp = &*p; |
Nope. In a declaration (int **pp), * tells the compiler it is a pointer. In an expression (&*p), * dereferences a pointer (gets the value it points to). & gets the address of the variable (aka a pointer to the variable).
So when you do &*p, you get this: *p is equal to int x, so &(*p) is equal to &(x) is equal to p.
What you want is a pointer to p, so you would do int **pp = &p.
pp = &p = &&x
x = *p = **pp
You can have infinite pointers or circular pointers or whatever you want.
void *a, *b;
(void **) a = &b; //tell compiler to pretend a is a double pointer
(void **) b = &a;
*a is b, **a is a, ***a is b, ****a is a
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Does that man you can make pointers to pointers to pointers and etc? And one more thing if you are going to use a pointer to a pointer would you set it up like this?
