RE: [Dev-C++] STL, iterators and pointers?

[Ioannis V. <no...@ya...>]

> -----Original Message-----
> From: dev...@li... 
> [mailto:dev...@li...] On Behalf 
> Of Phil Schulz
> Sent: Friday, July 06, 2001 4:17 AM
> To: dev...@li...
> Subject: [Dev-C++] STL, iterators and pointers?
> 
> 
> 
> Some questions about the STL containers and iterators.
> 
>  When you insert an object into a multiset (or list, etc.) 
> does it create a copy of the original Object, or does it 
> connect to the original? 


When you say "multiset" i consider that you mean standard library
container. When you create an object of a container type containing a
standard object type then the number specified of objects are created.

E.g..

vector<string> l(10); creates an array (vector) of 10 string objects
with the name l; These 10 string objects are created with the creation
of the vector.

so if we have string s="Test";

l[0]=s;

s is COPIED in l[0];


Now if you create a vector of pointers e.g.

vector<string *> pointers(10);

pointers[0]=&s;

pointer[0] is pointing to our string s;


> 
> and I'm not sure how to ask this next one:
> If you have an iterator for the above multiset, can you get a generic
> Object* out of it that points to the Object?  I tried taking 
> the addressof the dereferenced iterator ( &(*iter) ) but that 
> didn't seem to work out quite right...
> 

iterators act like pointers but they are not pointers. the &(*iter) of
yours should work. Perhaps the container contained pointers and not
objects?

e.g. vector<int *>integers(5);
integers[0]=new int(5); // it is like we assign then integers[0]=5;

vector<int *>::iterator iter=integers.begin();

int *p;

p=*iter // and NOT &(*iter) since the container contains pointers and
our iterator behaves like int **



> 
> Why I'm asking:
> I have two classes, Book and Author that each contain a 
> pointer to the other.
> 
> I have a multiset of Books, and a multiset of Authors. When I 
> add a new Book, I need to be able to link it to an Author, 
> and vice versa. The
> Book* I get when I make a new object doesn't correspond to 
> where the iterator is pointing. 


Probably you made some mistakes on the assignment, check what i wrote
above.


Ioannis

* Ioannis Vranos
* Programming pages: http://www.noicys.f2s.com
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