57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
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///////////////////////////////////////////////////////////////////////////////
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/// \file null.hpp
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/// Definintion of null_context\<\>, an evaluation context for
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/// proto::eval() that simply evaluates each child expression, doesn't
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/// combine the results at all, and returns void.
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//
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// Copyright 2008 Eric Niebler. Distributed under the Boost
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// Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_PROTO_CONTEXT_NULL_HPP_EAN_06_24_2007
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#define BOOST_PROTO_CONTEXT_NULL_HPP_EAN_06_24_2007
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#include <boost/preprocessor/iteration/iterate.hpp>
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#include <boost/preprocessor/repetition/repeat.hpp>
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#include <boost/proto/proto_fwd.hpp>
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#include <boost/proto/eval.hpp>
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#include <boost/proto/traits.hpp>
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namespace boost { namespace proto { namespace context
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{
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template<
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typename Expr
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, typename Context
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, long Arity // = Expr::proto_arity_c
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>
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struct null_eval
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{};
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template<typename Expr, typename Context>
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struct null_eval<Expr, Context, 0>
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{
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typedef void result_type;
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void operator()(Expr &, Context &) const
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{}
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};
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// Additional specializations generated by the preprocessor
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#include <boost/proto/context/detail/null_eval.hpp>
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/// null_context
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///
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struct null_context
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{
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/// null_context::eval
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///
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template<typename Expr, typename ThisContext = null_context const>
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struct eval
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: null_eval<Expr, ThisContext>
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{};
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};
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}}}
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#endif
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