I realize it's been ages since I started this conversation, but...


I find the idea that add_pointer does something so different from add_const
and add_reference disturbing, and hard-to-remember.

Could we call the current add_pointer<>  template addressof_type or
something, and supply an add_pointer which straightforwardly adds a '*' if
it's legal to do so?

-----------------------------------------------------------
           David Abrahams * Boost Consulting
dave@[...].com * http://www.boost-consulting.com

From: "David Abrahams" <david.abrahams@[...].com> 


>  I can understand why the behavior would be useful for references, but I
>  still can't understand it for arrays. A pointer-to-an-array is a
>  well-defined concept, but maybe there's something I'm missing here:
> 
>  template <class T>
>  struct holder
>  {
>      typedef T type;
>      T held;
>  };
> 
>  template <class T>
>  std::type_info const& f(T const& x)
>  {
>      typename add_pointer<typename T::type>::type held_ptr p = &x.held;
>      return typeid(*p);
>  }
> 
>  std::type_info id = f(holder<int[10]>());
> 
>  So, does this program compile? If so, what does id contain? typeid(int)?
>  typeid(int[10])? Something else?
> 
>  -Dave
> 
>  ----- Original Message -----
>  From: "John Maddock" <John_Maddock@[...].com>
>  To: <boost@[...].com>
>  Sent: Sunday, March 17, 2002 7:32 AM
>  Subject: Re: [boost] type_traits: add_pointer behavior?
> 
> 
>  > > On conforming compilers, add_pointer<int&> is int*.
>  > >
>  > > I'm not sure that's desirable (perhaps int& would be better).
>  > >
>  > > Also, add_pointer<int[5]> is int* rather than int(*)[5] on
>  conforming
>  > > compilers.
>  > >
>  > > I /really/ can't understand why you'd want to throw out the array
>  part.
>  > > It seems to me that any type_traits metafunction called "add_xxx"
>  > > shouldn't strip any features of its argument.
>  > >
>  > > Thoughts?
>  >
>  > The aim is that add_pointer<T>::type is the same as the type of &t, if
>  t is
>  > an instance of T.
>  >
>  > John Maddock
>  > http://ourworld.compuserve.com/homepages/john_maddock/index.htm
>  >
>  >




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