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72 lines
2.3 KiB
72 lines
2.3 KiB
3 years ago
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/*=============================================================================
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Copyright (c) 2001-2011 Joel de Guzman
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Copyright (c) 2006 Dan Marsden
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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(FUSION_VALUE_AT_IMPL_20060124_2129)
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#define FUSION_VALUE_AT_IMPL_20060124_2129
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#include <boost/fusion/support/config.hpp>
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#include <boost/fusion/container/vector/convert.hpp>
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#include <boost/fusion/algorithm/transformation/transform.hpp>
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#include <boost/fusion/sequence/intrinsic/value_at.hpp>
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#include <boost/type_traits/remove_reference.hpp>
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#include <boost/fusion/support/unused.hpp>
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#include <boost/mpl/eval_if.hpp>
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#include <boost/mpl/identity.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/config.hpp>
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namespace boost { namespace fusion {
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struct zip_view_tag;
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namespace detail
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{
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template<typename N>
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struct poly_value_at
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{
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template<typename T>
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struct result;
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template<typename N1, typename Seq>
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struct result<poly_value_at<N1>(Seq)>
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: mpl::eval_if<is_same<Seq, unused_type const&>,
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mpl::identity<unused_type>,
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result_of::value_at<typename remove_reference<Seq>::type, N> >
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{};
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// never called, but needed for decltype-based result_of (C++0x)
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#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
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template<typename Seq>
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BOOST_FUSION_GPU_ENABLED
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typename result<poly_value_at(Seq)>::type
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operator()(Seq&&) const;
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#endif
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};
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}
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namespace extension
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{
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template<typename Tag>
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struct value_at_impl;
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template<>
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struct value_at_impl<zip_view_tag>
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{
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template<typename Sequence, typename N>
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struct apply
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{
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typedef typename result_of::transform<
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typename Sequence::sequences,
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detail::poly_value_at<N> >::type values;
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typedef typename result_of::as_vector<values>::type type;
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};
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};
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}
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}}
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#endif
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