[boost] [iterator] New Specialized Adaptors ? (was : interest in pair projection iterators?)

From: Loïc Joly (loic.joly_at_[hidden])
Date: 2006-12-21 11:11:50

I resurect an old post :

David Abrahams a écrit :
> Simon Buchan <simon_at_[hidden]> writes:
> 
>>>>The idea is to define a template class,
[...]
>>>>which overloads operator*() and operator->() to access the element named 
>>>>"first" of the object returned by Iterator::operator*(). (With something 
>>>>analagous for second_iterator_t.) A function named first_iterator() 
>>>>provides a convenient creation function a-la std::make_pair().
[...]
>   struct get_first
>   {
>       template <class T>
>       typename T::first_type& operator()(T& x) const
>       {
>           return x.first;
>       }
> 
>       template <class T>
>       typename T::first_type const& operator()(T const& x) const
>       {
>           return x.first;
>       }
>   };
> 
>   // similar get_second
> 
>   transform_iterator<get_first, Iterator>

Hello,

I think this kind of adapter is quite usefull and of broad usage, and I 
think it should be part of the iterators provided by default in the 
Iterator library, just like indirect_iterator. Or at least put is as a 
real life example of what can be done with transform_iterator.

Regards,

-- 
Loïc