Ticket #1601: boost_tuple_iterator.hpp.patch

boost/fusion/adapted/boost_tuple/boost_tuple_iterator.hpp

@@ -14 +14 @@
 #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 +94 @@
                 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>