[Boost-bugs] [Boost C++ Libraries] #8313: const definition of boost::none

Subject: [Boost-bugs] [Boost C++ Libraries] #8313: const definition of boost::none
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-03-20 11:32:52

#8313: const definition of boost::none
------------------------------+---------------------------------------------
 Reporter:  anonymous         |       Owner:  fcacciola
     Type:  Bugs              |      Status:  new      
Milestone:  To Be Determined  |   Component:  optional 
  Version:  Boost 1.52.0      |    Severity:  Problem  
 Keywords:                    |  
------------------------------+---------------------------------------------
 boost provides an object named boost::none of type boost::none_t. it
 originally stems from Boost.Optional, but since it is in the root
 directory, boost/none.hpp, I guess it is there for other uses as well.

 I tried to use it in the following way, which fails, because of the
 definition of boost::none:

 template<class T,class T2=boost::none_t>
 struct A{
     A(T &a,T2 &b=none);
 };

 boost::none is an object defined to be const, so it is not accepted as a
 non-const reference. I don't see a reason why it has to be const. its
 value is never used anyway.

 I'll probably have to use boost::enable_if instead, to enable a "unary"
 constructor if and only if T2 == boost::none_t

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8313>
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