[Boost-bugs] [Boost C++ Libraries] #10403: fusion make_map metafunction

Subject: [Boost-bugs] [Boost C++ Libraries] #10403: fusion make_map metafunction
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-08-26 10:34:33

#10403: fusion make_map metafunction
-----------------------------------------+---------------------
 Reporter:  Wojciech Mamrak <wmamrak@…>  |      Owner:  djowel
     Type:  Bugs                         |     Status:  new
Milestone:  To Be Determined             |  Component:  fusion
  Version:  Boost 1.56.0                 |   Severity:  Problem
 Keywords:  fusion make_map              |
-----------------------------------------+---------------------
 Hello,

 It seems documentation is out-of-sync with implementation of fusion's
 make_map metafunction, and also the new implementation (using variadic
 templates) is inconsistent with previous ones.

 The docs [1] say:
 result_of::make_map<int, double, char, double>::type

 make_map is implemented as a metafunction class, i.e. it does not have a
 nested type typedef:
         template <typename ...Key>
         struct make_map
         {
             template <typename ...T>
             struct apply
             {
                 typedef map<
                     fusion::pair<
                         Key
                       , typename detail::as_fusion_element<T>::type
                     >...>
                 type;
             };
         };

 so the proper "call" would be:
 result_of::make_map<int, double>::apply<char, double>::type

 From this I conclude it is not only a documentation error, but also api
 breach. Presumably it got unnoticed since make_map function is not using
 make_map metafunction anymore (as opposed to what the docs claim [2]).

 regards


 [1]
 http://www.boost.org/doc/libs/1_56_0/libs/fusion/doc/html/fusion/container/generation/metafunctions/make_map.html

 [2]
 http://www.boost.org/doc/libs/1_56_0/libs/fusion/doc/html/fusion/container/generation/functions/make_map.html

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/10403>
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