From e82ddaed3896c42c63987da98f916f13a6af5e12 Mon Sep 17 00:00:00 2001
From: Tobias Schwinger <tschwinger@isonews2.com>
Date: Mon, 19 Mar 2007 18:13:24 +0000
Subject: [PATCH] support for sequences weaker than Forward Sequence

[SVN r37230]
---
 .../zip_view/detail/strictest_traversal.hpp   | 33 +++++++++----------
 .../sequence/view/zip_view/zip_view.hpp       | 15 +++++++--
 2 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/include/boost/fusion/sequence/view/zip_view/detail/strictest_traversal.hpp b/include/boost/fusion/sequence/view/zip_view/detail/strictest_traversal.hpp
index 33ff347e..b6c43fa9 100644
--- a/include/boost/fusion/sequence/view/zip_view/detail/strictest_traversal.hpp
+++ b/include/boost/fusion/sequence/view/zip_view/detail/strictest_traversal.hpp
@@ -15,7 +15,7 @@
 #include <boost/fusion/sequence/intrinsic/mpl.hpp>
 #include <boost/fusion/algorithm/iteration/fold.hpp>
 #include <boost/type_traits/remove_reference.hpp>
-#include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/is_convertible.hpp>
 
 namespace boost { namespace fusion {
     
@@ -25,6 +25,19 @@ namespace boost { namespace fusion {
 
     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;
+        };
+
         template<typename Next, typename StrictestSoFar>
         struct strictest_traversal_impl
         {
@@ -32,23 +45,7 @@ namespace boost { namespace fusion {
             typedef typename traits::category_of<
                 typename remove_reference<Next>::type>::type tag2;
 
-            typedef typename mpl::or_<
-                is_same<tag1, fusion::forward_traversal_tag>,
-                is_same<tag2, fusion::forward_traversal_tag> >::type 
-            has_forward_traversal;
-
-            typedef typename mpl::or_<
-                is_same<tag1, fusion::bidirectional_traversal_tag>,
-                is_same<tag2, fusion::bidirectional_traversal_tag> >::type
-            has_bidirectional_traversal;
-
-            typedef typename mpl::if_<
-                has_forward_traversal,
-                forward_traversal_tag,
-                typename mpl::if_<
-                has_bidirectional_traversal,
-                bidirectional_traversal_tag,
-                random_access_traversal_tag>::type>::type type;
+            typedef typename stricter_traversal<tag1,tag2>::type type;
         };
 
         template<typename Sequence>
diff --git a/include/boost/fusion/sequence/view/zip_view/zip_view.hpp b/include/boost/fusion/sequence/view/zip_view/zip_view.hpp
index f3bc5cd9..9668abed 100644
--- a/include/boost/fusion/sequence/view/zip_view/zip_view.hpp
+++ b/include/boost/fusion/sequence/view/zip_view/zip_view.hpp
@@ -47,10 +47,21 @@ namespace boost { namespace fusion {
 
         struct seq_ref_size
         {
-            template<typename Seq>
+            template<typename Seq, 
+                typename SeqClass = typename remove_reference<Seq>::type, 
+                bool HasSize = traits::is_forward<SeqClass>::value
+                >
             struct result
-                : result_of::size<typename remove_reference<Seq>::type>
+                : result_of::size<SeqClass>
             {};
+
+            static int const int_max = static_cast<int>(
+                static_cast<unsigned>(~0) >> 1);
+
+            template<typename Seq, typename SeqClass>
+            struct result<Seq, SeqClass, false>
+                : mpl::int_<int_max>
+            {}; 
         };
 
         struct poly_min