Re: [boost] [iterator] Idea for "range_from_ref_iterator"

From: David Abrahams (dave_at_[hidden])
Date: 2006-04-09 12:14:46

Ion Gaztañaga <igaztanaga_at_[hidden]> writes:

> Hi to all,
>
>   Trying to simplify containers' code in Boost.Interprocess, I've seen 
> that an iterator that simulates a range of values from a single value is 
> useful to implement functions taking a value and a count in containers:
>
> template<class T, class A>
> class vector
> {
>     //...
>     void insert (iterator position, size_type n, const T& x);
>     void assign (size_type n, const T& x);
> };
>
> My intention was to reuse the code for "insert" and "assign" taking
> iterators to avoid nearly duplicating the code (which is quite complex 
> in vector, deque and basic_string). This way, I've created
> an iterator called "range_from_ref_iterator" that can be used to 
> implement the "insert" function taking a value and a count like this:

You haven't really explained what this thing is supposed to be doing.
As far as I can tell from the code, it dereferences to the same
location at each position.  If that's really what you intend, you
ought to do something to ensure that its iterator category doesn't
indicate it satisfies forward iterator requirements.

> Do you think this iterator is a good addition to boost iterator library? 
> Obviously it can be more refined. It could take the external value by 
> reference or store a copy depending on the type. But I think it can be 
> useful. I'm open to write the documentation following Boost.Iterator 
> style if this iterator is considered useful (I'm open also to let others 
> do the hard work, of course). Comments?

Seems like a reasonable idea, but I'm not sure whether it's useful
enough to be included.  I'd definitely call it something other than
range_from_ref_iterator, though.  constant_iterator or something like
that seems appropriate.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com