ceph/src/boost/boost/spirit/home/support/unused.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2011 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_UNUSED_APRIL_16_2006_0616PM)
   9 #define BOOST_SPIRIT_UNUSED_APRIL_16_2006_0616PM
  10
  11 #if defined(_MSC_VER)
  12 #pragma once
  13 #endif
  14
  15 #include <boost/config.hpp>
  16 #include <boost/mpl/bool.hpp>
  17
  18 #if defined(BOOST_MSVC)
  19 # pragma warning(push)
  20 # pragma warning(disable: 4522) // multiple assignment operators specified warning
  21 #endif
  22
  23 ///////////////////////////////////////////////////////////////////////////////
  24 namespace boost { namespace spirit
  25 {
  26     ///////////////////////////////////////////////////////////////////////////
  27     // We do not import fusion ::unused_type anymore to avoid boost::fusion
  28     // being turned into an associate namespace for boost::spirit, as this
  29     // interferes with ADL in unexpected ways. We rather copy the full
  30     // unused_type implementation from boost::fusion.
  31     ///////////////////////////////////////////////////////////////////////////
  32     struct unused_type
  33     {
  34         unused_type()
  35         {
  36         }
  37
  38         template <typename T>
  39         unused_type(T const&)
  40         {
  41         }
  42
  43         template <typename T>
  44         unused_type const&
  45         operator=(T const&) const
  46         {
  47             return *this;
  48         }
  49
  50         template <typename T>
  51         unused_type&
  52         operator=(T const&)
  53         {
  54             return *this;
  55         }
  56
  57         unused_type const&
  58         operator=(unused_type const&) const
  59         {
  60             return *this;
  61         }
  62
  63         unused_type&
  64         operator=(unused_type const&)
  65         {
  66             return *this;
  67         }
  68     };
  69
  70     unused_type const unused = unused_type();
  71
  72     namespace detail
  73     {
  74         struct unused_only
  75         {
  76             unused_only(unused_type const&) {}
  77         };
  78     }
  79
  80     template <typename Out>
  81     inline Out& operator<<(Out& out, detail::unused_only const&)
  82     {
  83         return out;
  84     }
  85
  86     template <typename In>
  87     inline In& operator>>(In& in, unused_type&)
  88     {
  89         return in;
  90     }
  91
  92     ///////////////////////////////////////////////////////////////////////////
  93     namespace traits
  94     {
  95         // We use this test to detect if the argument is not an unused_type
  96         template <typename T> struct not_is_unused : mpl::true_ {};
  97         template <> struct not_is_unused<unused_type> : mpl::false_ {};
  98     }
  99 }}
 100
 101 #if defined(BOOST_MSVC)
 102 # pragma warning(pop)
 103 #endif
 104
 105 #endif