Re: [Boost-users] [STL] An question about list::iterator

From: KSpam (keesling_spam_at_[hidden])
Date: 2007-11-02 12:09:48

Max,

VS2005 uses checked iterators.  The additional checking prevents many misuses 
of STL containers.

> list<int> alist;
> alist.push_back(1);
>
> list<int>::iterator it_NULL;	// denotes a NULL iterator
> list<int>::iterator it_beg = alist.begin();
>
> std::cout << boolalpha;
> std::cout << "(it_NULL == it_beg) " << (it_NULL == it_beg) << endl;

Here it_begin is an iterator to the alist container, and it_NULL is an 
iterator that does not have an associated container.  Since the iterators 
point to different containers, they cannot be compared.  This is a good 
thing :-)

> What's wrong? Or any other alternative solution available?
> Thanks in advance for any help.

The checked iterators kept you from doing something that you shouldn't be 
doing.  You can turn off checked iterators by throwing some defines during 
compilation (I think any third-party libs that you link to would have to 
throw the same defines).  Trust me when I say that you do not want to turn 
checked iterators off.  It is quite embarrassing how many times checked 
iterators have found silly bugs in my code :-)

I would suggest coming up with a different construct to test for NULL.

Justin