Re: [boost] append_iterator

From: Kevin Spinar (spinarkm_at_[hidden])
Date: 2006-10-26 20:13:45

On 10/26/06, Jason Hise <0xchaos_at_[hidden]> wrote:
> Does boost provide any sort of iterator adapter which can be used as a
> forward iterator through a collection, but which will act like an
> output iterator upon reaching the end and push back new values?  I am
> looking for something which will allow me to build a collection as
> though I was using an output iterator, but will also allow me to save
> copies of the current iterator so that I can modify the values they
> point to later.
>
> If there isn't, should I roll my own, or is there a better way to do
> what I want?

Why don't you simply clear the collection first and use
std::back_inserter?  I suppose if there are more elements in the
container than you write to this iterator, you'd want the remaining
elements unaffected.

> If I do roll my own, would people be interested in seeing it developed
> into a boost library?

It doesn't seem that such an iterator would be used nearly often
enough to warrant inclusion into boost.  People generally either need
a std::back_inserter or simply the container's forward iterator, not a
combination of the two.  Perhaps if you could provide several use
cases, this iterator would seem more valuable and not an iterator
which is used only in your specific project.

> Sidenote: This iterator adapter would require push_back to not
> invalidate existing iterators (other than end).  Therefore, a special
> iterator might need to be specified when wrapping certain collections.
>  For instance, random access containers (vector and deque) would
> probably need iterators that stored an integer index and a pointer to
> the container, because push_back would be likely to result in memory
> reallocations.
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Kevin Spinar