Re: [Boost-users] [Iterators] iterators over char *

Subject: Re: [Boost-users] [Iterators] iterators over char *
From: Rao, Anant (Anant.Rao_at_[hidden])
Date: 2010-11-02 00:46:05

Thanks Krzysztof, Patrick!

While it’s true that a char* seems to be equivalent to an iterator (in this case), I prefer the iterator/reverse_iterator much better. For example, if I use an iterator and it reaches end(), I can do
--it to  get to the last char.

In a char * model, once I reach the NULL ptr (at the end of the string), I can’t back-track. Similarly, rbegin()/reverse_iter. Maintaining a sentinel value for the start of a string is more difficult (other than indices). IMHO, those are the solid advantages I see with an iterator.

I re-read the article published by David Abrahams et al on ‘reverse_iterator’ (http://www.boost.org/doc/libs/1_44_0/libs/iterator/doc/reverse_iterator.html_)
and felt it’s adequate for my purposes. Basically, I will use that reverse_iterator for both fwd and reverse traversals by using ++ and --.

A  couple  of simple questions I have:


-          Why is it not possible to define a boost::iterator as easily as a boost::reverse_iterator on a char * string  as in the above web link? (Again, it doesn’t block me – as I mentioned, I’ll just use a reverse_iter and use ++ and – on it to satisfy my needs. More of curiosity).

-          Looks like boost::reverse_iterator can’t be assigned to; can only be created. If I need to define it as a class member that needs to be made to point to diff strings as the program progresses, it doesn’t seem to be possible. So, I’m thinking of using a ptr to a boost::reverse_iterator so that I can re-seat the reverse_iterator to diff strings. Is this a convoluted approach or correct approach (given my needs)? If former, what’d be the correct approach?

Thanks again,
Anant



From: boost-users-bounces_at_[hidden] [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Patrick Horgan
Sent: Monday, November 01, 2010 4:34 PM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Iterators] iterators over char *

On 11/01/2010 01:16 PM, Rao, Anant wrote:

Hi,

I have a ‘char *’. I need to be able to traverse thru the string in both fwd and reverse directions.
A char* is a reversible iterator already.  Reversible iterators are modeled to look like pointers.

Patrick



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