Fix for ticket #6000

[SVN r74873]

include/boost/fusion/algorithm/transformation/pop_back.hpp

@@ -78,6 +78,51 @@ namespace boost { namespace fusion
               , mpl::int_<(Last::is_last?1:0)>
             >::type
         {};
+
+
+        template <typename Iterator, bool IsLast_>
+        struct prior_impl
+        {
+            typedef typename Iterator::iterator_base_type base_type;
+
+            typedef typename
+                result_of::prior<base_type>::type
+            base_prior;
+
+            typedef pop_back_iterator<base_prior, false> type;
+
+            static type
+            call(Iterator const& i)
+            {
+                return type(fusion::prior(i.iterator_base));
+            }
+    };
+
+        template <typename Iterator>
+        struct prior_impl<Iterator, true>
+        {
+            // If this is the last iterator, we'll have to double back
+            typedef typename Iterator::iterator_base_type base_type;
+
+            typedef typename
+                result_of::prior<
+                  typename result_of::prior<base_type>::type
+                >::type
+            base_prior;
+
+            typedef pop_back_iterator<base_prior, false> type;
+
+            static type
+            call(Iterator const& i)
+            {
+                return type(fusion::prior(
+                    fusion::prior(i.iterator_base)));
+            }
+        };
+
+        template <typename Iterator>
+        struct prior : prior_impl<Iterator, Iterator::is_last>
+        {};
     };
 
     namespace result_of

test/algorithm/pop_back.cpp

@@ -15,6 +15,9 @@
 #include <boost/fusion/algorithm/transformation/pop_back.hpp>
 #include <boost/fusion/algorithm/transformation/push_back.hpp>
 #include <boost/fusion/algorithm/query/find.hpp>
+#include <boost/fusion/include/back.hpp>
+#include <boost/fusion/include/array.hpp>
+#include <boost/array.hpp>
 #include <boost/mpl/vector_c.hpp>
 
 int
@@ -85,12 +88,17 @@ main()
         auto i1 = find<int>(popv);
         auto i2 = find<double>(pop);
 
-        assert(i1 != end(pop));
+        BOOST_TEST(i1 != end(pop));
-        assert(i2 != end(pop));
+        BOOST_TEST(i2 != end(pop));
-        assert(i1 != i2);
+        BOOST_TEST(i1 != i2);
     }
 #endif
 
+    {
+        boost::array<std::size_t, 2> a = { 10, 50 };
+        BOOST_TEST(back(pop_back(a)) == 10);
+    }
+
     return boost::report_errors();
 }