83 lines
2.3 KiB
C++
83 lines
2.3 KiB
C++
/*=============================================================================
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Copyright (c) 2001-2011 Joel de Guzman
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Copyright (c) 2001-2011 Hartmut Kaiser
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#if !defined(BOOST_SPIRIT_UNUSED_APRIL_16_2006_0616PM)
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#define BOOST_SPIRIT_UNUSED_APRIL_16_2006_0616PM
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/config.hpp>
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#include <boost/mpl/bool.hpp>
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///////////////////////////////////////////////////////////////////////////////
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namespace boost { namespace spirit
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{
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///////////////////////////////////////////////////////////////////////////
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// We do not import fusion ::unused_type anymore to avoid boost::fusion
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// being turned into an associate namespace for boost::spirit, as this
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// interferes with ADL in unexpected ways. We rather copy the full
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// unused_type implementation from boost::fusion.
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///////////////////////////////////////////////////////////////////////////
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struct unused_type
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{
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BOOST_DEFAULTED_FUNCTION(unused_type(), {})
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template <typename T>
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unused_type(T const&)
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{
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}
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template <typename T>
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unused_type const&
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operator=(T const&) const
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{
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return *this;
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}
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template <typename T>
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unused_type&
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operator=(T const&)
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{
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return *this;
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}
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};
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unused_type const unused = unused_type();
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namespace detail
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{
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struct unused_only
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{
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unused_only(unused_type const&) {}
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};
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}
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template <typename Out>
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inline Out& operator<<(Out& out, detail::unused_only const&)
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{
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return out;
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}
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template <typename In>
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inline In& operator>>(In& in, unused_type&)
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{
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return in;
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}
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///////////////////////////////////////////////////////////////////////////
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namespace traits
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{
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// We use this test to detect if the argument is not an unused_type
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template <typename T> struct not_is_unused : mpl::true_ {};
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template <> struct not_is_unused<unused_type> : mpl::false_ {};
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}
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}}
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#endif
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