[boost] Re: boost::transform_iterator and boost::lambda functors

From: David Abrahams (dave_at_[hidden])
Date: 2004-06-10 14:47:40

"Maxim Yegorushkin" <e-maxim_at_[hidden]> writes:

> David Abrahams <dave_at_[hidden]> wrote:
>
>>> Am I missing something? Is there a way to avoid using
>> result_type_wrapper<>?
>> You could use boost::make_adaptable from
>> boost/bind/make_adaptable.hpp, but there really ought to be a
>> version of make_transform_iterator that does that for you.
>
> Shame on me. I knew about boost/bind/make_adaptable.hpp but I thought
> it could only be used with a bind functor and did not give it a try.
>
> I wonder, why doesn't boost::lambda::ret<> privide that functionality
> of boost::make_adaptable<>? It would certainly made sense and saved me
> and hopefully other people from troubles.

It can't.  The result type of the lambda expression depends on its
inputs.  result_type is only one type.  Adaptable functions are
fundamentally non-polymorphic.

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