On Thu, Jun 10, 2004 at 03:47:40PM -0400, David Abrahams wrote:
"Maxim Yegorushkin" <e-maxim@yandex.ru> writes:
David Abrahams <dave@boost-consulting.com> 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.
Maxim is talking about ret<>, which has a monomorphic type: http://www.boost.org/libs/lambda/doc/ar01s05.html#sect:overriding_deduced_re... I think it would be both possible and valuable for ret<T> and bind<T> to define result_type. -- -Brian McNamara (lorgon@cc.gatech.edu)