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Pointers and such...

Started by jim bob Jan 8, 2002 at 8:45 PM 4 replies 450+ views

Original Post

Jan 8, 2002 at 8:45 PM

Yes, I know this is a very basic question, but I wanted to know more for clarification, since I see things done two ways. If you do this: int bob; int *x; // x is a pointer to an integer x = &bob // x points to address of bob Is that the same as this: int bob; int *x = &bob / x points to address of bob Or do those mean two different things? And if you do this: int tom; int *x = &tom Would *x hold the address of tom, and x hold the value of tom? Is that correct? And would changing x to 27 make tom 27, or changing tom to 100, make x 100? Any clarification on these things would be helpful. While programming in C, what do the -> operators mean? I don''t really know what they are called, so I can''t look up information on them. Thanks all. I am not worthy of a sig!

Drakkor

Jan 8, 2002 at 9:42 PM

int bob;
int * x;
x = &bob

is the same as

int bob;
int * x = &bob

it just saves a line of code

x holds the address of bob and *x holds the value of bob. Think of * as ''contents of'' when dereferencing a variable. Remember, x is a pointer, so it only holds an address.

D

Dobbs

Jan 8, 2002 at 10:51 PM

Drakkor is totally right, but just to clarify your second question:

int tom;
int *x = &tom

It might look, as you thought, like *x is holding the address of tom, but it''s not. In this instance you''re using the * to declare the pointer not to dereference it, so as usual x will hold the address and *x will hold the value.

The -> is called "pointer to member notation," it might have some other names too but that''s what I''ve seen it called. If you have a pointer to a struct or an object you use -> to simultaneously dereference it and access its fields and methods. So if class CObject has field foo and method bar:

CObject myObj= new CObject();
myObj->foo = myObj->bar();

instead of something like:

CObject myObj = new CObject();
(*myObj).foo = (*myObj).bar();

KwamiMatrix

Jan 9, 2002 at 12:02 AM

Dobbs, woundn't it be:

CObject *myObj= new CObject;
myObj->foo = myObj->bar;

Wouldn't

CObject myObj= new CObject();

be for Java?

Edem Attiogbe

Edited by - KwamiMatrix on January 9, 2002 1:04:23 AM

Martee

126

Martee

Jan 9, 2002 at 12:13 AM

It would indeed.

jim bob

Author

jim bob

Jan 9, 2002 at 5:53 AM

I got it now guys. Thank you!

I am not worthy of a sig!

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