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137 lines
3.9 KiB
137 lines
3.9 KiB
/*=============================================================================
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Copyright (c) 2001-2011 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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#if !defined(FUSION_AT_IMPL_07172005_0726)
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#define FUSION_AT_IMPL_07172005_0726
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#include <boost/fusion/support/config.hpp>
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#include <boost/fusion/support/detail/access.hpp>
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#include <boost/type_traits/is_const.hpp>
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#include <boost/type_traits/add_const.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/mpl/bool.hpp>
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namespace boost { namespace fusion
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{
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namespace detail
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{
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template <typename Cons>
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struct cons_deref
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{
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typedef typename Cons::car_type type;
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};
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template <typename Cons, int I>
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struct cons_advance
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{
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typedef typename
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cons_advance<Cons, I-1>::type::cdr_type
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type;
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};
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template <typename Cons>
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struct cons_advance<Cons, 0>
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{
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typedef Cons type;
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};
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template <typename Cons>
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struct cons_advance<Cons, 1>
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{
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typedef typename Cons::cdr_type type;
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};
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template <typename Cons>
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struct cons_advance<Cons, 2>
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{
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#if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
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typedef typename Cons::cdr_type::cdr_type type;
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#else
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typedef typename Cons::cdr_type _a;
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typedef typename _a::cdr_type type;
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#endif
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};
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template <typename Cons>
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struct cons_advance<Cons, 3>
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{
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#if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
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typedef typename Cons::cdr_type::cdr_type::cdr_type type;
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#else
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typedef typename Cons::cdr_type _a;
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typedef typename _a::cdr_type _b;
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typedef typename _b::cdr_type type;
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#endif
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};
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template <typename Cons>
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struct cons_advance<Cons, 4>
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{
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#if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
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typedef typename Cons::cdr_type::cdr_type::cdr_type::cdr_type type;
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#else
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typedef typename Cons::cdr_type _a;
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typedef typename _a::cdr_type _b;
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typedef typename _b::cdr_type _c;
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typedef typename _c::cdr_type type;
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#endif
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};
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}
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struct cons_tag;
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namespace extension
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{
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template <typename Tag>
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struct at_impl;
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template <>
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struct at_impl<cons_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 detail::cons_deref<
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typename detail::cons_advance<Sequence, N::value>::type>::type
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element;
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typedef typename
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mpl::if_<
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is_const<Sequence>
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, typename detail::cref_result<element>::type
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, typename detail::ref_result<element>::type
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>::type
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type;
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template <typename Cons, int N2>
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BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
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static type
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call(Cons& s, mpl::int_<N2>)
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{
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return call(s.cdr, mpl::int_<N2-1>());
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}
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template <typename Cons>
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BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
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static type
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call(Cons& s, mpl::int_<0>)
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{
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return s.car;
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}
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BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
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static type
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call(Sequence& s)
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{
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return call(s, mpl::int_<N::value>());
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}
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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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