Re: [boost] [TypeTraits] Type traits for member pointers?

Subject: Re: [boost] [TypeTraits] Type traits for member pointers?
From: John Maddock (john_at_[hidden])
Date: 2009-07-20 07:31:00

> Anyway, I'd like to point out that the member_object.hpp header linked to 
> by
> John Maddock is not actually what the tracking ticket he also linked
> to was asking for.
> It seems pretty clear to me that whoever posted that wanted something
> more like this:
>
> template<class T> struct remove_mem_ptr {
>    typedef T type;
> };
> template<class T, class In> struct remove_mem_ptr<T In::*> {
>    typedef T type;
> };
>
> template<class T, class In> struct add_mem_ptr {
>    typedef T In::*type;
> }; // (for completeness...)
>
> (Evidence: the person who posted that ticket said this:
>> Can boost::remove_pointer<T> be modified to work with
>> pointers-to-member (data), too? For instance: remove_pointer<int *>
>> returns the int type, but so should remove_pointer<int std::div_t::*>.
> ...implying that he wants remove_pointer<int std::div_t::*> to return
> int, not std::div_t.
> And member_object<int std::div_t::*> would return std::div_t.)

Not quite, there was some discussion on the mailing list about that feature 
request (including with the OP) and there was a clear consensus for *not* 
modifying remove_pointer, but for adding a new trait (which the OP was happy 
with as far as I recall).

The reason for not using the "obvious simple implementation" BTW is two 
fold:

* It doesn't work for all compilers.
* It doesn't handle compiler extensions like __fastcall etc.

HTH, John.