[boost] Re: [congif] BOOST_BEFRIEND_TEMPLATE, BOOST_PRIVATE

From: David Abrahams (dave_at_[hidden])
Date: 2005-03-06 03:30:06

"Jonathan Turkanis" <technews_at_[hidden]> writes:

> David Abrahams wrote:
>> "Peter Dimov" <pdimov_at_[hidden]> writes:
>>
>>> Jonathan Turkanis wrote:
>>>> David Abrahams wrote:
>>>>> "Peter Dimov" <pdimov_at_[hidden]> writes:
>>>>>
>>>>>>>          BOOST_BEFRIEND_TEMPLATE(shared_ptr, Y, 1)
>>>>>>>          BOOST_BEFRIEND_TEMPLATE(weak_ptr, Y, 1)
>>>>>>>          T * px;                     // contained pointer
>>>>>>>          detail::shared_count pn;    // reference counter
>>>>>>
>>>>>> This doesn't look any better to me than the original, sorry. ;-)
>>>>>
>>>>> I agree with Peter.  In fact, to me it looks significantly worse.
>>>>
>>>> Well, there's no accounting for taste. ;-) I use similar macros a
>>>> lot in the Preboost Interfaces library.
>>>
>>> This has nothing to do with taste. The original version of the code
>>> can be understood immediately as it only relies on general C++
>>> knowledge. The macro-based version adds a level of indirection; you
>>> now need to look at the documentation or the definition of the
>>> macros.
>>
>> Right.  It would be different if the macros significantly raised the
>> abstraction level, but they don't.
>
> The reason I like the macros is that you only need one version of
> the code,

I consider the #ifdef idiom to be only "one version of the code", when
I look at it.  I generally don't need protected members, so I put the
friends right between the public and private stuff, where it belongs:

  class fu
  {
   public:
          .
          .
          .
  #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
   private:  // template friends
      template<class Y> friend class shared_ptr;
      template<class Y> friend class weak_ptr;
  #endif

   private:  // data members
      T* px;
      detail::shared_count pn; 
  };

Clean and quiet.

> and -- if you find the macro names intuitive -- the version with the macros
> reads like the version for conforming compilers.

Just wait till you start needing nontype template parameters.

> It's basically the same idea as BOOST_USE_FACET.

Never had to use that one.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com