[Boost-bugs] [Boost C++ Libraries] #2887: boost::mersenne_twister copy constructor

Subject: [Boost-bugs] [Boost C++ Libraries] #2887: boost::mersenne_twister copy constructor
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-03-26 10:59:05

#2887: boost::mersenne_twister copy constructor
------------------------------+---------------------------------------------
 Reporter:  corlay_at_[hidden]  |       Owner:  no-maintainer
     Type:  Bugs              |      Status:  new          
Milestone:  Boost 1.39.0      |   Component:  random       
  Version:  Boost 1.38.0      |    Severity:  Problem      
 Keywords:  boost::random     |  
------------------------------+---------------------------------------------
 Compiled-generated copy constructor and assignment operator are fine, but
 the copy constructor is overloaded by mersenne_twister(Generator & gen) {
 seed(gen); } even is the Generator type is mersenne_twister;

 {{{
   template<class Generator>
   explicit mersenne_twister(Generator & gen) { seed(gen); }

   // compiler-generated copy ctor and assignment operator are fine
 }}}

 Hence calling
 {{{
         boost::mt19937 rng(0);
         boost::mt19937 rngcopy(rng);
         std::cout << (rng==rngcopy) << std::endl;
 }}}
 yields "false".

 Maybe a boost::disable_if<boost::is_same<mersenne_twister,Generator> >
 solves the problem.

 See also the workaround  made in default constructor of
 boost::pass_through_engine to avoid matching Generator & constructor

 S.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/2887>
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