/*=============================================================================
    Copyright (c) 2001-2014 Joel de Guzman
    Copyright (c) 2001-2011 Hartmut Kaiser

    Distributed under the Boost Software License, Version 1.0. (See accompanying
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
==============================================================================*/
#if !defined(BOOST_SPIRIT_X3_UNUSED_APRIL_16_2006_0616PM)
#define BOOST_SPIRIT_X3_UNUSED_APRIL_16_2006_0616PM

#include <iosfwd>

///////////////////////////////////////////////////////////////////////////////
namespace boost {
namespace spirit {
namespace x3 {
struct unused_type
{
    unused_type() = default;

    template <typename T>
    unused_type(T const&)
    {
    }

    template <typename T>
    unused_type const&
    operator=(T const&) const
    {
        return *this;
    }

    template <typename T>
    unused_type&
    operator=(T const&)
    {
        return *this;
    }

    // unused_type can also masquerade as an empty context (see context.hpp)

    template <typename ID>
    unused_type
    get(ID) const
    {
        return {};
    }

    friend std::ostream&
    operator<<(std::ostream& out, unused_type const&)
    {
        return out;
    }

    friend std::istream&
    operator>>(std::istream& in, unused_type&)
    {
        return in;
    }
};

constexpr auto unused = unused_type{};
}
}
}

#endif
