[boost] Re: [iterator] small feature request

From: David Abrahams (dave_at_[hidden])
Date: 2004-12-08 22:13:11

Eric Niebler wrote:
> The iterator_adaptor<> template has a base() function to access the 
> underlying iterator. Well and good. However, iterator_adaptor<> doesn't 
> have a public typedef for the iterator type returned from this function. 
> Can it be added?
> 
> Rationale:
> Given some iterator of type T that is built of an unknown number of 
> adaptors, extract the underlying iterator. Consider:
> 
>    template<class Iter>
>    typename disable_if<is_adapted<Iter>,Iter>::type
>    base(Iter const & it)
>    {
>      return it;
>    }
> 
>    template<class D,class B,class V,class T,class R,class Di>
>    ??????????
>    base(iterator_adaptor<D,B,V,T,R,Di> const & it)
>    {
>      return base(it.base());
>    }
> 
> I can't think of a way to write the return type of the second overload. 
> If iterator_adaptor had a nested typedef for its Base template 
> parameter, this would be very straightforward.

Seems reasonable.  Can you submit a patch?

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