[boost] Re: Library proposal --- pair (and tuple) iterators

From: Anthony Williams (anthony.williamsNOSPAM_at_[hidden])
Date: 2003-09-22 03:54:04

David Abrahams <dave_at_[hidden]> writes:
> Anthony Williams <anthony.williamsNOSPAM_at_[hidden]> writes:

>> I would like to submit my "pair iterators" library for inclusion in
>> boost. The library is described in my article "Pairing off Iterators" from
>> Overload 51, which is available at
>> http://cplusplus.anthonyw.cjb.net/pair_iterators.pdf

> I think you may be a little late.  Have you seen
> http://www.boost-consulting.com/boost/boost/iterator/zip_iterator.hpp
> ??

I hadn't. But then, you only checked it in two weeks ago. Does it work
correctly with things like this?

template<typename It>
void rotate_by_one(It begin,It end)
{
    typedef std::iterator_traits<It>::value_type ValueType;

    if(begin==end)
    {
        return;
    }
    ValueType value=*begin; // take a copy and keep it around
    
    for(It prev=begin++;begin!=end;++begin,++prev)
    {
        *prev=*begin; // overwrite the value copied
    }
    *prev=value; // use the copy
}

*that* was the bit that I found hardest to get working --- having a value type
such that *it was a real reference, writing to *it updated the underlying
iterators, yet copying from *it produced an object of the same type that
*didn't* update the underlying iterators.

If it does, then I'll let the Ublas guys know, since it was a request from
them to use my code that finally forced me to stop sitting around and submit
it (after all, the article in Overload was published October 2002).

Anthony
-- 
Anthony Williams
Senior Software Engineer, Beran Instruments Ltd.
Remove NOSPAM when replying, for timely response.