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

Subject: Re: [boost] [reference_wrapper] Overloading operator() in reference_wrapper
From: Kazutoshi Satoda (k_satoda_at_[hidden])
Date: 2013-05-02 12:35:11

On 2013/05/03 00:10 +0900, Nathan Crookston wrote:
> Peter Dimov wrote:
>> Kazutoshi Satoda wrote:
>>> The standard version has 4 member typedef which are conditionally
>>> defined: result_type, argument_type, first_argument_type,
>>> second_argument_type. ...
(snip)
>> Interesting. I've always considered these typedefs redundant, but this is
>> the first time I see them as actively harmful.
> 
> Yes, this is good to know.  I wondered why the standard bothered to specify
> that in our new, decltype-enabled world. ...

I can guess only one reason that the resulting functors are expected to
work with some C++03-style function adapters in some old libraries which
may have no plan to adapt C++11 features like decltype.

About the requirement of these typedefs in 20.8 [function.objects] p5
to enable standard adapters, I found that there is an open issue
LWG #2149 which is proposing to drop it.
http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#2149
> While not opposed to striking this paragraph, we will need the
> additional wording to fix the openning hole before this issue can move
> forward.

-- 
k_satoda