Re: [Boost-bugs] [Boost C++ Libraries] #1396: wrong result_of invocation around transform_view

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #1396: wrong result_of invocation around transform_view
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2007-11-29 02:49:25

#1396: wrong result_of invocation around transform_view
----------------------------------------------------+-----------------------
  Reporter:  Shunsuke Sogame <pstade.mb_at_[hidden]>  |       Owner:  djowel 
      Type:  Bugs                                   |      Status:  new    
 Milestone:  Boost 1.35.0                           |   Component:  fusion 
   Version:  Boost Development Trunk                |    Severity:  Problem
Resolution:                                         |    Keywords:         
----------------------------------------------------+-----------------------
Comment (by anonymous):

 IMO, you are wrong. It is correct. The example you have in the boost list
 thread certainly is ill formed. The example I have here is not.

 I've followed the thread (http://tinyurl.com/298abt) but what you missed
 is the template. The T in Fun(T) is generic and can accommodate references
 too. This(int) does not.

 If you want to avoid dangling references, you can write it as:
 {{{

 struct identity
 {
     template<class FunCall>
     struct result;

     template <class Fun, class T>
     struct result<Fun(T&)>
     {
         typedef T& type;
     };

     template <class Fun, class T>
     struct result<Fun(T const&)>
     {
         typedef T type;
     };

     template <class T>
     T& operator()(T& val) const
     {
         return val;
     }

     template <class T>
     T operator()(T const& val) const
     {
         return val;
     }
 };

 }}}

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/1396#comment:4>
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