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/*=============================================================================
Copyright (c) 2001-2011 Joel de Guzman
Copyright (c) 2006 Dan Marsden
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)
==============================================================================*/
#if !defined(FUSION_STRICTEST_TRAVERSAL_20060123_2101)
#define FUSION_STRICTEST_TRAVERSAL_20060123_2101
#include <boost/config.hpp>
#include <boost/mpl/or.hpp>
#include <boost/mpl/if.hpp>
#include <boost/fusion/support/category_of.hpp>
#include <boost/fusion/mpl.hpp>
#include <boost/fusion/algorithm/iteration/fold.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/type_traits/is_convertible.hpp>
namespace boost { namespace fusion
{
struct forward_traversal_tag;
struct bidirectional_traversal_tag;
struct random_access_traversal_tag;
namespace detail
{
template<typename Tag1, typename Tag2,
bool Tag1Stricter = boost::is_convertible<Tag2,Tag1>::value>
struct stricter_traversal
{
typedef Tag1 type;
};
template<typename Tag1, typename Tag2>
struct stricter_traversal<Tag1,Tag2,false>
{
typedef Tag2 type;
};
struct strictest_traversal_impl
{
template<typename Sig>
struct result;
template<typename StrictestSoFar, typename Next>
struct result<strictest_traversal_impl(StrictestSoFar, Next)>
{
typedef typename remove_reference<Next>::type next_value;
typedef typename remove_reference<StrictestSoFar>::type strictest_so_far;
typedef strictest_so_far tag1;
typedef typename traits::category_of<next_value>::type tag2;
typedef typename stricter_traversal<tag1,tag2>::type type;
};
// never called, but needed for decltype-based result_of (C++0x)
#ifndef BOOST_NO_RVALUE_REFERENCES
template<typename StrictestSoFar, typename Next>
typename result<strictest_traversal_impl(StrictestSoFar, Next)>::type
operator()(StrictestSoFar&&, Next&&) const;
#endif
};
template<typename Sequence>
struct strictest_traversal
: result_of::fold<
Sequence, fusion::random_access_traversal_tag,
strictest_traversal_impl>
{};
}
}}
#endif
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Swift