From c0eebc8121d8c38a90ba26587d3ea6d25026f41b Mon Sep 17 00:00:00 2001
From: Joel de Guzman <djowel@gmail.com>
Date: Fri, 10 Jul 2009 00:50:05 +0000
Subject: [PATCH] Fix #1601

[SVN r54850]
---
 .../boost_tuple/boost_tuple_iterator.hpp      | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/include/boost/fusion/adapted/boost_tuple/boost_tuple_iterator.hpp b/include/boost/fusion/adapted/boost_tuple/boost_tuple_iterator.hpp
index fca135e5..cf3183b1 100644
--- a/include/boost/fusion/adapted/boost_tuple/boost_tuple_iterator.hpp
+++ b/include/boost/fusion/adapted/boost_tuple/boost_tuple_iterator.hpp
@@ -14,6 +14,9 @@
 #include <boost/mpl/if.hpp>
 #include <boost/mpl/eval_if.hpp>
 #include <boost/mpl/or.hpp>
+#include <boost/mpl/plus.hpp>
+#include <boost/mpl/int.hpp>
+#include <boost/mpl/apply.hpp>
 #include <boost/tuple/tuple.hpp>
 
 namespace boost { namespace fusion
@@ -91,6 +94,39 @@ namespace boost { namespace fusion
                 return type(iter.cons.get_tail());
             }
         };
+        
+        template <typename I1, typename I2>
+        struct distance;
+
+        // detail
+        template <typename I1, typename I2>
+        struct lazy_next_distance
+        {
+            typedef
+                typename mpl::plus<
+                    mpl::int_<1>,
+                    typename distance<
+                        typename next<I1>::type,
+                        I2
+                    >::type
+                >::type type;
+        };
+        
+        template <typename I1, typename I2>
+        struct distance
+        {
+            typedef typename mpl::eval_if<
+                boost::is_same<I1, I2>,
+                mpl::int_<0>,
+                lazy_next_distance<I1, I2>
+            >::type type;
+            
+            static type
+            call(I1 const&, I2 const&)
+            {
+                return type();
+            }
+        };
     };
 
     template <typename Null>