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-rw-r--r--boost/compute/lambda/placeholders.hpp93
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+//---------------------------------------------------------------------------//
+// Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
+//
+// 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
+//
+// See http://boostorg.github.com/compute for more information.
+//---------------------------------------------------------------------------//
+
+#ifndef BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
+#define BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
+
+#include <boost/mpl/has_xxx.hpp>
+
+#include <boost/compute/lambda/context.hpp>
+#include <boost/compute/lambda/result_of.hpp>
+
+namespace boost {
+namespace compute {
+namespace lambda {
+
+namespace mpl = boost::mpl;
+namespace proto = boost::proto;
+
+// lambda placeholders
+expression<proto::terminal<placeholder<0> >::type> const _1;
+expression<proto::terminal<placeholder<1> >::type> const _2;
+expression<proto::terminal<placeholder<2> >::type> const _3;
+
+namespace detail {
+
+BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
+
+template<class T, bool HasResultType>
+struct terminal_type_impl;
+
+template<class T>
+struct terminal_type_impl<T, true>
+{
+ typedef typename T::result_type type;
+};
+
+template<class T>
+struct terminal_type_impl<T, false>
+{
+ typedef T type;
+};
+
+template<class T>
+struct terminal_type
+{
+ typedef typename terminal_type_impl<T, has_result_type<T>::value>::type type;
+};
+
+} // end detail namespace
+
+// result_of placeholders
+template<class Args>
+struct result_of<expression<proto::terminal<placeholder<0> >::type>, Args, proto::tag::terminal>
+{
+ typedef typename boost::tuples::element<0, Args>::type arg_type;
+
+ typedef typename detail::terminal_type<arg_type>::type type;
+};
+
+template<class Args>
+struct result_of<expression<proto::terminal<placeholder<1> >::type>, Args, proto::tag::terminal>
+{
+ typedef typename boost::tuples::element<1, Args>::type arg_type;
+
+ typedef typename detail::terminal_type<arg_type>::type type;
+};
+
+template<class Args>
+struct result_of<expression<proto::terminal<placeholder<2> >::type>, Args, proto::tag::terminal>
+{
+ typedef typename boost::tuples::element<2, Args>::type arg_type;
+
+ typedef typename detail::terminal_type<arg_type>::type type;
+};
+
+} // end lambda namespace
+
+// lift lambda placeholders up to the boost::compute namespace
+using lambda::_1;
+using lambda::_2;
+using lambda::_3;
+
+} // end compute namespace
+} // end boost namespace
+
+#endif // BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP