Re: [boost] member function traits (was: Concept Traits Library)

Subject: Re: [boost] member function traits (was: Concept Traits Library)
From: John Maddock (boost.regex_at_[hidden])
Date: 2010-07-13 08:35:15

>> I think a separate traits class for extracting the member type from a 
>> pointer to member is the best solution here, lets say it's called 
>> "remove_member_pointer" (finding a good name is the main stumbling block 
>> really), then you could use:
>>
>> function_traits<typename 
>> remove_member_pointer<member_function_type>::type>::arity etc
>
> O yes, that would be a good solution too. I'm interested in it.
>
>>
>> BTW the problem with extending function_traits is that it operates on 
>> function-types, and not on pointers or references to functions, but there 
>> is no such type as a "member function", only a pointer to one, so we 
>> would end up with different behaviors for member functions and regular 
>> ones.
> Well, in my view the behaviour would be equal, but they would require just 
> some additional specializations (plus the trick to avoid add_pointer).
>
> Actually I don't exactly see why function_traits should not operate on 
> pointers. The function_traits_helper operates on pointers and not on 
> types. So what actually happens is that the user removes the pointer, and 
> it is then added in the function_traits, and specialized on in the 
> details. No problem of course, but you could specialize on function-types 
> AND function-pointers separately to avoid the requirement of using 
> remove_pointer.

Nod.

> But, again, a remove_member_pointer, if it can be implemented, would do. 
> Is it already implemented or drafted somewhere? Because we cannot wait to 
> use it ;-)

It's here: 
https://svn.boost.org/trac/boost/browser/sandbox/type_traits/boost/type_traits/remove_member_pointer.hpp

John.