| /*============================================================================= |
| Copyright (c) 2001-2006 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/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; |
| }; |
| }; |
| |
| template<typename Sequence> |
| struct strictest_traversal |
| : result_of::fold< |
| Sequence, fusion::random_access_traversal_tag, |
| strictest_traversal_impl> |
| {}; |
| |
| } |
| }} |
| |
| #endif |