[boost] Re: std::sort(zip_iterator...) does not compile

From: David Abrahams (dave_at_[hidden])
Date: 2004-07-22 09:39:07

Anthony Williams <anthony_w.geo_at_[hidden]> writes:

> Gunter Winkler <guwi17_at_[hidden]> writes:
>
>> I tried to use boost::zip_iterator to sort 2 parallel arrays. Unfortunatly
>> gcc does not compile the appended example because it can not convert
>>
>>    boost::detail::iterator_category_with_traversal<std::input_iterator_tag, 
>>    boost::random_access_traversal_tag>
>>
>> to either 
>>   std::bidirectional_iterator_tag
>> or
>>   std::random_access_iterator_tag.
>> Thus it cannot dispatch the correct stl::__copy_backward() procedure.
>>
>> Is sort() not yet supported? 
>
> As Dave already posted, zip_iterator doesn't support return forward or
> bidirectional iterators, so std::sort() cannot be used.
>
> What you need is something like my tuple iterator (tupleit.zip from the files
> area on the boost yahoo group), which *does* support use with std::sort ---
> the iterator category of the tuple iterator is the minimum category of the
> supplied iterators.

How can sorting work?
What type is returned from its operator* ?

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com