Re: [Boost-bugs] [Boost C++ Libraries] #2857: change return type of the c_array() member function

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #2857: change return type of the c_array() member function
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-03-18 17:32:33

#2857: change return type of the c_array() member function
-----------------------------------+----------------------------------------
  Reporter:  hervemart1_at_[hidden]  |       Owner:  no-maintainer
      Type:  Patches               |      Status:  new          
 Milestone:  Boost 1.39.0          |   Component:  array        
   Version:  Boost 1.38.0          |    Severity:  Cosmetic     
Resolution:                        |    Keywords:               
-----------------------------------+----------------------------------------

Comment(by niels_dekker):

 David Abrahams and I just mailed about the issue and we agreed that it
 would be preferable to have such a function as a non-member. Because
 tr1::array doesn't have a c_array() member function and std::array
 probably won't have one either. (See
 [http://home.roadrunner.com/~hinnant/issue_review/lwg-active.html#930 LWG
 issue 930, Access to std::array data as built-in array type])  Such a
 boost::get_c_array(arg) function could be overloaded to support both
 std::array and boost::array.
 So it could be implemented as follows:

 {{{

   // Specific for boost::array: simply returns its elems data member.
   template <typename T, std::size_t N>
   T(&get_c_array(boost::array<T,N>& arg))[N]
   {
     return arg.elems;
   }

   // Const version.
   template <typename T, std::size_t N>
   const T(&get_c_array(const boost::array<T,N>& arg))[N]
   {
     return arg.elems;
   }

   // Overload for std::array, assuming that std::array will have
   // explicit conversion functions as discussed at the WG21 meeting
   // in Summit, March 2009.
   template <typename T, std::size_t N>
   T(&get_c_array(std::array<T,N>& arg))[N]
   {
     return static_cast<T(&)[N]>(arg);
   }

   // Const version.
   template <typename T, std::size_t N>
   const T(&get_c_array(const std::array<T,N>& arg))[N]
   {
     return static_cast<T(&)[N]>(arg);
   }
 }}}

 When rvalue references are supported, get_c_array could be overloaded for
 rvalue  arrays as well.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/2857#comment:2>
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