Re: [boost] [reference_wrapper] Overloading operator() in reference_wrapper

Subject: Re: [boost] [reference_wrapper] Overloading operator() in reference_wrapper
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2013-04-09 12:07:24

On Tue, Apr 9, 2013 at 12:24 AM, Nathan Crookston <
nathan.crookston_at_[hidden]> wrote:

> Hi all,
>
> std::reference_wrapper includes an overload of operator()[1] which allows a
> wrapped function object to be called without needing to first unwrap:
>
> #include <boost/ref.hpp>
> #include <functional>
> #include <iostream>
>
> int main()
> {
>   auto f = [](int i) { std::cout << i * 2 << std::endl; };
>   std::ref(f)(5);//change this to boost::ref and it will not compile.
> }
>
> I think it would be valuable to update boost::ref to match the standard
> version.  On compilers which support variadic templates and rvalue
> references the code is obvious.  Those which support one or neither could
> still have overloads for some number of arguments.
>
> This would be handy in a few places, notably
> boost::gil::for_each_pixel[2].  I know that boost::bind + reference wrapper
> could be used instead (boost::bind(boost::ref(f), 5)).  Given that
> implementing operator() is relatively simple, and that the standard object
> based on boost::reference_wrapper has it (rather than requiring std::bind),
> I'd argue that this change is desirable.
>
> Thanks,
> Nate
>
> [1]
>
> http://en.cppreference.com/w/cpp/utility/functional/reference_wrapper/operator%28%29
> [2]http://comments.gmane.org/gmane.comp.lang.c%2B%2B.isocpp.general/513

+1

- Jeff