/Src/Dependencies/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///////////////////////////////////////////////////////////////////////////////
 24namespace 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