ceph/src/boost/libs/spirit/include/boost/spirit/home/x3/support/unused.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     Copyright (c) 2001-2011 Hartmut Kaiser
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 ==============================================================================*/
   8 #if !defined(BOOST_SPIRIT_X3_UNUSED_APRIL_16_2006_0616PM)
   9 #define BOOST_SPIRIT_X3_UNUSED_APRIL_16_2006_0616PM
  10
  11 #include <ostream>
  12 #include <istream>
  13 #include <boost/mpl/identity.hpp>
  14
  15 #if defined(BOOST_MSVC)
  16 # pragma warning(push)
  17 # pragma warning(disable: 4522) // multiple assignment operators specified warning
  18 #endif
  19
  20 ///////////////////////////////////////////////////////////////////////////////
  21 namespace boost { namespace spirit { namespace x3
  22 {
  23     struct unused_type
  24     {
  25         unused_type()
  26         {
  27         }
  28
  29         template <typename T>
  30         unused_type(T const&)
  31         {
  32         }
  33
  34         template <typename T>
  35         unused_type const&
  36         operator=(T const&) const
  37         {
  38             return *this;
  39         }
  40
  41         template <typename T>
  42         unused_type&
  43         operator=(T const&)
  44         {
  45             return *this;
  46         }
  47
  48         unused_type const&
  49         operator=(unused_type const&) const
  50         {
  51             return *this;
  52         }
  53
  54         unused_type&
  55         operator=(unused_type const&)
  56         {
  57             return *this;
  58         }
  59
  60         // unused_type can also masquerade as an empty context (see context.hpp)
  61
  62         template <typename ID>
  63         unused_type get(ID) const
  64         {
  65             return {};
  66         }
  67     };
  68
  69     auto const unused = unused_type{};
  70
  71     inline std::ostream& operator<<(std::ostream& out, unused_type const&)
  72     {
  73         return out;
  74     }
  75
  76     inline std::istream& operator>>(std::istream& in, unused_type&)
  77     {
  78         return in;
  79     }
  80 }}}
  81
  82 #if defined(BOOST_MSVC)
  83 # pragma warning(pop)
  84 #endif
  85
  86 #endif