[Boost-bugs] [Boost C++ Libraries] #4357: mpl::equal for associative sequences

Subject: [Boost-bugs] [Boost C++ Libraries] #4357: mpl::equal for associative sequences
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-06-17 07:51:29

#4357: mpl::equal for associative sequences
------------------------------+---------------------------------------------
 Reporter:  anonymous         |       Owner:  agurtovoy
     Type:  Feature Requests  |      Status:  new      
Milestone:  Boost 1.43.0      |   Component:  mpl      
  Version:  Boost 1.44.0      |    Severity:  Problem  
 Keywords:                    |  
------------------------------+---------------------------------------------
 this is not a bug, as the current behaviour is documented correctly, but I
 think mpl::equal<> should return equality for mpl::set<>s that are equal
 but are not in the same sequence.
 something like:

 struct equal :
   mpl::and_<
     mpl::equal_to<
       mpl::size<Set1>,
       mpl::size<Set2>
     >,
     mpl::fold<
       Set1,
       mpl::true_,
       mpl::and_<
         mpl::_1,
         mpl::has_key<Set2,mpl::_2>
       >
     >
   >{};

 also I think it would be usable for equal sets to be runtime-convertible.

 template<...>
 struct set{
   template<class OtherSet>
   set(OtherSet,typename enable_if<equal<set,OtherSet> >::type *e=0){}
 };

 so you can do this:

 void f(set<e1,e2>);

 f(set<e2,e1>());

 the same might be usable for mpl::map.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4357>
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