Re: [boost] How to detect if f() returns void or not?

Subject: Re: [boost] How to detect if f() returns void or not?
From: Eric Niebler (eric_at_[hidden])
Date: 2009-12-15 01:56:18

Edward Diener wrote:
> David Abrahams wrote:
>> On Dec 14, 2009, at 8:40 PM, Edward Diener wrote:
>>
>>> Eric Niebler wrote:
>>>> Frédéric Bron wrote:
>>>>> I would like to detect if the return type of a function is void or not
>>>>> within C++03 standard?
>>>> <snip>
>>>> I solved this problem once while writing a different trait and 
>>>> documented it here:
>>>> http://www.boost.org/doc/libs/1_41_0/doc/html/proto/appendices.html#boost_proto.appendices.implementation.function_arity 
>>>>
>>> It's extremely clever, as others have noted, but I am wondering if 
>>> there is any website, or possibly newsgroup, devoted to advanced TMP 
>>> techniques such as yours.
>>
>> We had a short discussion of the limitations of that technique here: 
>> http://cpp-next.com/archive/2009/10/this-week-in-boost/comment-page-1/#comment-228 
> 
> I don't understand from your link what those limitations are, although 
> it appears it revolves around the comma operator technique used by Eric 
> Niebler in his example.

I think the point is that if the expression returns a type that has 
itself overloaded the comma operator, then that overload may get 
selected, trowing the whole thing off-track. (I'm sure someone will 
correct me if I've read it too quickly and missed the point.) Anyway, 
that's worth noting, but hardly seems likely to occur in practice.

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com