61 lines
1.7 KiB
Plaintext
61 lines
1.7 KiB
Plaintext
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/*==============================================================================
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Copyright (c) 2005-2010 Joel de Guzman
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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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#ifndef BOOST_PHOENIX_CORE_NOTHING_HPP
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#define BOOST_PHOENIX_CORE_NOTHING_HPP
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#include <boost/phoenix/core/limits.hpp>
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#include <boost/mpl/void.hpp>
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#include <boost/phoenix/core/actor.hpp>
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#include <boost/phoenix/core/call.hpp>
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#include <boost/phoenix/core/expression.hpp>
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#include <boost/phoenix/core/value.hpp>
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namespace boost { namespace phoenix
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{
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/////////////////////////////////////////////////////////////////////////////
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//
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// null_actor
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//
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// An actor that does nothing (a "bum", if you will :-).
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//
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/////////////////////////////////////////////////////////////////////////////
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namespace detail
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{
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struct nothing {};
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}
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namespace expression
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{
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struct null
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: expression::value<detail::nothing>
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{};
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}
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template<typename Dummy>
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struct is_custom_terminal<detail::nothing, Dummy>
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: mpl::true_
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{};
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template<typename Dummy>
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struct custom_terminal<detail::nothing, Dummy>
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{
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typedef void result_type;
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template <typename Context>
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void operator()(detail::nothing, Context &) const
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{
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}
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};
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typedef expression::null::type nothing_type BOOST_ATTRIBUTE_UNUSED;
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#ifndef BOOST_PHOENIX_NO_PREDEFINED_TERMINALS
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nothing_type const BOOST_ATTRIBUTE_UNUSED nothing = {{{}}};
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#endif
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}}
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#endif
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