94 lines
2.5 KiB
C++
94 lines
2.5 KiB
C++
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//---------------------------------------------------------------------------//
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// Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
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//
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// Distributed under the Boost Software License, Version 1.0
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// See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt
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//
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// See http://boostorg.github.com/compute for more information.
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//---------------------------------------------------------------------------//
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#ifndef BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
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#define BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
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#include <boost/mpl/has_xxx.hpp>
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#include <boost/compute/lambda/context.hpp>
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#include <boost/compute/lambda/result_of.hpp>
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namespace boost {
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namespace compute {
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namespace lambda {
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namespace mpl = boost::mpl;
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namespace proto = boost::proto;
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// lambda placeholders
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expression<proto::terminal<placeholder<0> >::type> const _1;
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expression<proto::terminal<placeholder<1> >::type> const _2;
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expression<proto::terminal<placeholder<2> >::type> const _3;
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namespace detail {
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BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
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template<class T, bool HasResultType>
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struct terminal_type_impl;
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template<class T>
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struct terminal_type_impl<T, true>
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{
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typedef typename T::result_type type;
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};
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template<class T>
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struct terminal_type_impl<T, false>
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{
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typedef T type;
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};
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template<class T>
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struct terminal_type
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{
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typedef typename terminal_type_impl<T, has_result_type<T>::value>::type type;
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};
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} // end detail namespace
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// result_of placeholders
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template<class Args>
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struct result_of<expression<proto::terminal<placeholder<0> >::type>, Args, proto::tag::terminal>
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{
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typedef typename boost::tuples::element<0, Args>::type arg_type;
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typedef typename detail::terminal_type<arg_type>::type type;
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};
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template<class Args>
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struct result_of<expression<proto::terminal<placeholder<1> >::type>, Args, proto::tag::terminal>
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{
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typedef typename boost::tuples::element<1, Args>::type arg_type;
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typedef typename detail::terminal_type<arg_type>::type type;
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};
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template<class Args>
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struct result_of<expression<proto::terminal<placeholder<2> >::type>, Args, proto::tag::terminal>
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{
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typedef typename boost::tuples::element<2, Args>::type arg_type;
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typedef typename detail::terminal_type<arg_type>::type type;
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};
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} // end lambda namespace
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// lift lambda placeholders up to the boost::compute namespace
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using lambda::_1;
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using lambda::_2;
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using lambda::_3;
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} // end compute namespace
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} // end boost namespace
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#endif // BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
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