Re: [boost] boost::result_of and C++03

From: Eric Niebler (eric_at_[hidden])
Date: 2008-04-09 21:07:09

Peter Dimov wrote:
> Eric Niebler:
> 
>> I'm glad we know how to write the identity function object in C++0x.
>> What about in C++03?
> 
> I'd put the C++03 overloads in an #else block; apart from that, this 
> identity function object is correct. 

OK, thanks. Just for my own understanding, leaving the C++03 overloads 
in -- as well as the nested result<> template -- doesn't make it wrong, 
correct? Just not minimal.

IIUC, this has implications for people wanting to write TR1-style 
function objects today. I think Shunsuke may be right in that we need an 
rvalue_wrapper so that it is possible to write function objects that 
will continue to work unmodified in C++0x. That is, my use of 
reference_wrapper to carry lvalue-ness has it backwards. T const & 
should be assumed to be a const lvalue, because it will mean that 
unambiguously in C++0x.

FWIW, I think fusion::make_vector()'s use of reference_wrapper is also 
incorrect. :-(

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com