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79 lines
2.6 KiB
79 lines
2.6 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_STRICTEST_TRAVERSAL_20060123_2101)
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#define FUSION_STRICTEST_TRAVERSAL_20060123_2101
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#include <boost/fusion/support/config.hpp>
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#include <boost/config.hpp>
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#include <boost/mpl/or.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/fusion/support/category_of.hpp>
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#include <boost/fusion/mpl.hpp>
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#include <boost/fusion/algorithm/iteration/fold.hpp>
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#include <boost/type_traits/remove_reference.hpp>
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#include <boost/type_traits/is_convertible.hpp>
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namespace boost { namespace fusion
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{
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struct forward_traversal_tag;
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struct bidirectional_traversal_tag;
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struct random_access_traversal_tag;
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namespace detail
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{
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template<typename Tag1, typename Tag2,
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bool Tag1Stricter = boost::is_convertible<Tag2,Tag1>::value>
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struct stricter_traversal
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{
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typedef Tag1 type;
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};
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template<typename Tag1, typename Tag2>
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struct stricter_traversal<Tag1,Tag2,false>
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{
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typedef Tag2 type;
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};
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struct strictest_traversal_impl
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{
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template<typename Sig>
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struct result;
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template<typename StrictestSoFar, typename Next>
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struct result<strictest_traversal_impl(StrictestSoFar, Next)>
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{
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typedef typename remove_reference<Next>::type next_value;
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typedef typename remove_reference<StrictestSoFar>::type strictest_so_far;
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typedef strictest_so_far tag1;
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typedef typename traits::category_of<next_value>::type tag2;
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typedef typename stricter_traversal<tag1,tag2>::type type;
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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 StrictestSoFar, typename Next>
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BOOST_FUSION_GPU_ENABLED
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typename result<strictest_traversal_impl(StrictestSoFar, Next)>::type
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operator()(StrictestSoFar&&, Next&&) const;
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#endif
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};
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template<typename Sequence>
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struct strictest_traversal
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: result_of::fold<
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Sequence, fusion::random_access_traversal_tag,
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strictest_traversal_impl>
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{};
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}
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}}
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#endif
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