insert_range empty sequences bug fix

[SVN r22336]

include/boost/mpl/aux_/insert_range_impl.hpp

@@ -17,12 +17,11 @@
 #ifndef BOOST_MPL_AUX_INSERT_RANGE_IMPL_HPP_INCLUDED
 #define BOOST_MPL_AUX_INSERT_RANGE_IMPL_HPP_INCLUDED
 
-#include "boost/mpl/iter_fold_backward.hpp"
-#include "boost/mpl/fold_backward.hpp"
+#include "boost/mpl/copy_backward.hpp"
 #include "boost/mpl/clear.hpp"
 #include "boost/mpl/push_front.hpp"
-#include "boost/mpl/identity.hpp"
-#include "boost/mpl/apply_if.hpp"
+#include "boost/mpl/iterator_range.hpp"
+#include "boost/mpl/begin_end.hpp"
 #include "boost/mpl/aux_/void_spec.hpp"
 #include "boost/mpl/aux_/iter_push_front.hpp"
 #include "boost/mpl/aux_/traits_lambda_spec.hpp"
@@ -35,29 +34,6 @@ namespace mpl {
 // specializing either the |insert_range_traits| or the primary 
 // |insert_range| template
 
-namespace aux {
-
-template<
-      typename Pos
-    , typename Range
-    >
-struct iter_range_inserter
-{
-    template< typename Sequence, typename Iterator > struct apply
-    {
-        typedef typename aux::iter_push_front<
-              typename apply_if<
-                  is_same<Pos,typename Iterator::next>
-                , fold_backward< Range, Sequence, push_front<_,_> >
-                , identity<Sequence>
-                >::type
-            , Iterator
-            >::type type;
-    };
-};
-
-} // namespace aux
-
 
 template< typename Tag >
 struct insert_range_traits
@@ -69,10 +45,22 @@ struct insert_range_traits
         >
     struct algorithm
     {
-        typedef typename iter_fold_backward<
-              Sequence
+        typedef typename copy_backward<
+              iterator_range<Pos, typename end<Sequence>::type>
             , typename clear<Sequence>::type
-            , aux::iter_range_inserter<Pos,Range>
+            , push_front<_,_> 
+            >::type first_part_;
+        
+        typedef typename copy_backward< 
+              Range
+            , first_part_
+            , push_front<_,_> 
+            >::type second_part_;
+        
+        typedef typename copy_backward<
+              iterator_range<typename begin<Sequence>::type,Pos>
+            , second_part_
+            , push_front<_,_>
             >::type type;
     };
 };

test/insert_range.cpp

@@ -17,6 +17,7 @@
 #include "boost/mpl/insert_range.hpp"
 #include "boost/mpl/find.hpp"
 #include "boost/mpl/list_c.hpp"
+#include "boost/mpl/list.hpp"
 #include "boost/mpl/size.hpp"
 #include "boost/mpl/range_c.hpp"
 #include "boost/mpl/equal.hpp"
@@ -32,5 +33,14 @@ int main()
 
     BOOST_STATIC_ASSERT(mpl::size<range>::type::value == 10);
     BOOST_STATIC_ASSERT((mpl::equal< range,mpl::range_c<int,0,10> >::type::value));
+
+    typedef mpl::insert_range<
+                mpl::list0<>,
+                mpl::end< mpl::list0<> >::type,
+                mpl::list<int>
+            >::type result2;
+    
+    BOOST_STATIC_ASSERT((mpl::size<result2>::type::value == 1));
+
     return 0;
 }