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

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-06-10 15:11:59

David Abrahams wrote:
> "Maxim Yegorushkin" <e-maxim_at_[hidden]> writes:
>
>> David Abrahams <dave_at_[hidden]> wrote:
>>
>> 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.

The result type of ret<R>(expr) is always R. That's what it does. That's
_all_ it does. ;-)

http://www.boost.org/libs/lambda/doc/ar01s05.html#sect:overriding_deduced_return_type

The result type of bind<R>(...) is also R, and the TR1 bind requires a
::result_type in this case, but lambda doesn't conform yet.