[Boost-bugs] [Boost C++ Libraries] #7633: Wanted: a way to force a nested result_type

Subject: [Boost-bugs] [Boost C++ Libraries] #7633: Wanted: a way to force a nested result_type
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-11-02 23:53:36

#7633: Wanted: a way to force a nested result_type
------------------------------+---------------------------------------------
 Reporter:  dave              |       Owner:  theller
     Type:  Bugs              |      Status:  new    
Milestone:  To Be Determined  |   Component:  phoenix
  Version:  Boost 1.52.0      |    Severity:  Problem
 Keywords:                    |  
------------------------------+---------------------------------------------
 For example, I had to use this:

 {{{#!c++
 template <class F> struct void_function : F
 {
     typedef void result_type;
     void_function(F x) : F(x) {}
 };

 template <class F>
 void_function<F> make_void(F x)
 {
     return void_function<F>(x);
 }
 }}}

 in order to get the following to work:

 {{{#!c++
 inline std::ostream& operator<<(std::ostream& s, my_variant const& x)
 {
     using namespace boost::phoenix::placeholders;
     using namespace boost::phoenix;

     boost::apply_visitor( make_void(s << arg1), x );
     //                    ^^^^^^^^^ HERE
     return s;
 }
 }}}

 Some libraries, like Boost.Variant, don't follow the {{{result_of}}}
 protocol.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7633>
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