Re: [boost] [result_of] Allow result_of to work with C++11 lambdas

Subject: Re: [boost] [result_of] Allow result_of to work with C++11 lambdas
From: Peter Dimov (lists_at_[hidden])
Date: 2013-04-27 12:40:38

Daniel Walker wrote:
> On Apr 21, 2013, at 10:36 PM, Peter Dimov <lists_at_[hidden]> wrote:
>
> > I can't think of a reason to ever use TR1 (and whichever version of 
> > result_of) in C++11. Even less so in C++14, which will have deduced 
> > return types unless the N3638 formal motion failed, and I very much hope 
> > it did not.
>
> Agreed, and we recommend in the boost::result_of documentation that C++11 
> users use std::result_of rather than boost::result_of.

I actually meant that C++11 users should use decltype directly rather than 
result_of.

A library that wanted to support both would do something like

template<...>

#if C++11

auto f(...) -> decltype(...)

#else

boost::result_of<...>::type f(...)

#endif

{ ... }

That's not very nice as it forces you to write everything twice, but it 
keeps C++11 users isolated from anything C++03-related. In particular, it no 
longer matters whether boost::result_of works with lambdas. (Well... it 
could matter if decltype is not N32whatever but lambdas work fine, but 
ideally, it shouldn't.)