change the return type from the indexed adaptor so that the index is available from the range element.

doc/reference/adaptors/indexed.qbk

@@ -7,14 +7,60 @@
 
 [table
     [[Syntax] [Code]]
+    [[Pipe] [`rng | boost::adaptors::indexed()`]]
     [[Pipe] [`rng | boost::adaptors::indexed(start_index)`]]
+    [[Function] [`boost::adaptors::index(rng)`]]
     [[Function] [`boost::adaptors::index(rng, start_index)`]]
 ]
 
-* [*Returns:] A range adapted to return both the element and the associated index. The returned range consists of iterators that have in addition to the usual iterator member functions an `index()` member function that returns the appropriate index for the element in the sequence corresponding with the iterator.
+[heading Description]
+The index within each returned `boost::range::index_value` is equal to
+`start_index` + the offset of the element from the beginning of the range. In
+the versions of the functions that omit `start_index` the starting index is
+taken to be `0`.
+
+* [*Purpose:] Adapt `rng` to return elements that have the corresponding value
+from `rng` and a numeric index.
+* [*Returns:] A range adapted to return both the element and the associated
+index. The returned range has elements of type:
+
+``
+boost::range::index_value<
+    typename boost::range_reference<decltype(rng)>::type,
+    typename boost::range_difference<decltype(rng)>::type
+>
+``
+
+The synopsis of index_value is as follows:
+``
+template<class T, class Indexable=std::ptrdiff_t>
+class index_value : public boost::tuple<Indexable, T>
+{
+public:
+
+    typedef ...unspecified...       index_type;
+    typedef ...unspecified...       const_index_type;
+
+    typedef ...unspecified...       value_type;
+    typedef ...unspecified...       const_value_type;
+
+    // ...unspecified... constructors
+
+    index_type index();
+    const_index_type index() const;
+
+    value_type value();
+    const_value_type value() const;
+};
+``
+
 * [*Range Category:] __single_pass_range__
 * [*Range Return Type:] `boost::indexed_range<decltype(rng)>`
-* [*Returned Range Category:] The range category of `rng`
+* [*Returned Range Category:] The range category of `rng` if and only if `rng`
+is not a __bidirectional_range__. If `rng` is a __bidirectional_range__ then the
+returned range category is __forward_range__. The rationale for the demotion of
+__bidirectional_range__ inputs to __forward_range__ is to avoid slow calculation
+of indices for `boost::end(rng)`.
 
 [section:indexed_example indexed example]
 [import ../../../test/adaptor_test/indexed_example.cpp]

include/boost/range/adaptor/indexed.hpp

@@ -1,71 +1,218 @@
-// Boost.Range library
+//  Copyright 2014 Neil Groves
 //
-//  Copyright Thorsten Ottosen, Neil Groves 2006 - 2008. Use, modification and
+//  Copyright (c) 2010 Ilya Murav'jov
-//  distribution is subject to the Boost Software License, Version
+// 
-//  1.0. (See accompanying file LICENSE_1_0.txt or copy at
+//  Use, modification and distribution is subject to the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 //  http://www.boost.org/LICENSE_1_0.txt)
 //
-// For more information, see http://www.boost.org/libs/range/
+// Credits:
+//  My (Neil's) first indexed adaptor was hindered by having the underlying
+//  iterator return the same reference as the wrapped iterator. This meant that
+//  to obtain the index one had to get to the index_iterator and call the
+//  index() function on it. Ilya politely pointed out that this was useless in
+//  a number of scenarios since one naturally hides the use of iterators in
+//  good range-based code. Ilya provided a new interface (which has remained)
+//  and a first implementation. Much of this original implementation has
+//  been simplified and now supports more compilers and platforms.
 //
+#ifndef BOOST_RANGE_ADAPTOR_INDEXED_HPP_INCLUDED
+#define BOOST_RANGE_ADAPTOR_INDEXED_HPP_INCLUDED
 
-#ifndef BOOST_RANGE_ADAPTOR_INDEXED_IMPL_HPP
+#include <boost/range/config.hpp>
-#define BOOST_RANGE_ADAPTOR_INDEXED_IMPL_HPP
-
-#include <boost/config.hpp>
-#ifdef BOOST_MSVC
-#pragma warning( push )
-#pragma warning( disable : 4355 )
-#endif
-
 #include <boost/range/adaptor/argument_fwd.hpp>
 #include <boost/range/iterator_range.hpp>
+#include <boost/range/traversal.hpp>
+#include <boost/range/size.hpp>
 #include <boost/range/begin.hpp>
 #include <boost/range/end.hpp>
-#include <boost/range/concepts.hpp>
+#include <boost/mpl/if.hpp>
-#include <boost/iterator/iterator_adaptor.hpp>
+#include <boost/type_traits/is_convertible.hpp>
 
+#include <boost/iterator/iterator_traits.hpp>
+#include <boost/iterator/iterator_facade.hpp>
 
+#include <boost/tuple/tuple.hpp>
 
 namespace boost
 {
     namespace adaptors
     {
-        // This structure exists to carry the parameters from the '|' operator
+
-        // to the index adapter. The expression rng | indexed(1) instantiates
+struct indexed
-        // this structure and passes it as the right-hand operand to the
+{
-        // '|' operator.
+    explicit indexed(std::ptrdiff_t x = 0)
-        struct indexed
+        : val(x)
     {
-            explicit indexed(std::size_t x) : val(x) {}
+    }
-            std::size_t val;
+    std::ptrdiff_t val;
+};
+
+    } // namespace adaptors
+
+    namespace range
+    {
+
+// Why yet another "pair" class:
+// - std::pair can't store references
+// - no need for typing for index type (default to "std::ptrdiff_t"); this is
+// useful in BOOST_FOREACH() expressions that have pitfalls with commas
+//   ( see http://www.boost.org/doc/libs/1_44_0/doc/html/foreach/pitfalls.html )
+// - meaningful access functions index(), value()
+template<class T, class Indexable = std::ptrdiff_t>
+class index_value
+    : public tuple<Indexable, T>
+{
+    typedef tuple<Indexable, T> base_t;
+
+    template<int N>
+    struct iv_types
+    {
+        typedef typename tuples::element<N, base_t>::type n_type;
+
+        typedef typename tuples::access_traits<n_type>::non_const_type non_const_type;
+        typedef typename tuples::access_traits<n_type>::const_type const_type;
     };
+
+public:
+    typedef typename iv_types<0>::non_const_type index_type;
+    typedef typename iv_types<0>::const_type const_index_type;
+    typedef typename iv_types<1>::non_const_type value_type;
+    typedef typename iv_types<1>::const_type const_value_type;
+
+    index_value()
+    {
     }
 
-    namespace range_detail
+    index_value(typename tuples::access_traits<Indexable>::parameter_type t0,
+                typename tuples::access_traits<T>::parameter_type t1)
+        : base_t(t0, t1)
     {
-        template< class Iter >
+    }
-        class indexed_iterator
+
-            : public boost::iterator_adaptor< indexed_iterator<Iter>, Iter >
+    // member functions index(), value() (non-const and const)
+    index_type index()
     {
-        private:
+        return boost::tuples::get<0>(*this);
-            typedef boost::iterator_adaptor< indexed_iterator<Iter>, Iter >
+    }
-                  base;
 
-            typedef BOOST_DEDUCED_TYPENAME base::difference_type index_type;
+    const_index_type index() const
+    {
+        return boost::tuples::get<0>(*this);
+    }
 
-            index_type m_index;
+    value_type value()
+    {
+        return boost::tuples::get<1>(*this);
+    }
+
+    const_value_type value() const
+    {
+        return boost::tuples::get<1>(*this);
+    }
+};
+
+    } // namespace range
+
+namespace range_detail
+{
+
+template<typename Iter>
+struct indexed_iterator_value_type
+{
+    typedef ::boost::range::index_value<
+        typename iterator_reference<Iter>::type,
+        typename iterator_difference<Iter>::type
+    > type;
+};
+
+// Meta-function to get the traversal for the range and therefore iterator
+// returned by the indexed adaptor for a specified iterator type.
+//
+// Random access -> Random access
+// Bidirectional -> Forward
+// Forward -> Forward
+// SinglePass -> SinglePass
+//
+// The rationale for demoting a Bidirectional input to Forward is that the end
+// iterator cannot cheaply have an index computed for it. Therefore I chose to
+// demote to forward traversal. I can maintain the ability to traverse randomly
+// when the input is Random Access since the index for the end iterator is cheap
+// to compute.
+template<typename Iter>
+struct indexed_traversal
+{
+private:
+    typedef typename iterator_traversal<Iter>::type wrapped_traversal;
+
+public:
+
+    typedef typename mpl::if_<
+        is_convertible<wrapped_traversal, random_access_traversal_tag>,
+        random_access_traversal_tag,
+        typename mpl::if_<
+            is_convertible<wrapped_traversal, bidirectional_traversal_tag>,
+            forward_traversal_tag,
+            wrapped_traversal
+        >::type
+    >::type type;
+};
+
+template<typename Iter>
+class indexed_iterator
+    : public iterator_facade<
+            indexed_iterator<Iter>,
+            typename indexed_iterator_value_type<Iter>::type,
+            typename indexed_traversal<Iter>::type,
+            typename indexed_iterator_value_type<Iter>::type,
+            typename iterator_difference<Iter>::type
+        >
+{
+public:
+    typedef Iter wrapped;
+
+private:
+    typedef iterator_facade<
+        indexed_iterator<wrapped>,
+        typename indexed_iterator_value_type<wrapped>::type,
+        typename indexed_traversal<wrapped>::type,
+        typename indexed_iterator_value_type<wrapped>::type,
+        typename iterator_difference<wrapped>::type
+    > base_t;
+
+public:
+    typedef typename base_t::difference_type difference_type;
+    typedef typename base_t::reference reference;
+    typedef typename base_t::difference_type index_type;
 
-        public:
     indexed_iterator()
-            : m_index(index_type()) {}
+        : m_it()
-            
+        , m_index()
-            explicit indexed_iterator( Iter i, index_type index )
-            : base(i), m_index(index)
     {
-                BOOST_ASSERT( m_index >= 0 && "Indexed Iterator out of bounds" );
     }
 
-            index_type index() const
+    template<typename OtherWrapped>
+    indexed_iterator(
+        const indexed_iterator<OtherWrapped>& other,
+        typename enable_if<is_convertible<OtherWrapped, wrapped> >::type* = 0
+    )
+        : m_it(other.get())
+        , m_index(other.get_index())
+    {
+    }
+
+    explicit indexed_iterator(wrapped it, index_type index)
+        : m_it(it)
+        , m_index(index)
+    {
+    }
+
+    wrapped get() const
+    {
+        return m_it;
+    }
+
+    index_type get_index() const
     {
         return m_index;
     }
@@ -73,100 +220,151 @@ namespace boost
  private:
     friend class boost::iterator_core_access;
 
+    reference dereference() const
+    {
+        return reference(m_index, *m_it);
+    }
+
+    bool equal(const indexed_iterator& other) const
+    {
+        return m_it == other.m_it;
+    }
+
     void increment()
     {
         ++m_index;
-                ++(this->base_reference());
+        ++m_it;
     }
 
-
     void decrement()
     {
-                BOOST_ASSERT( m_index > 0 && "Indexed Iterator out of bounds" );
+        BOOST_ASSERT_MSG(m_index > 0, "indexed Iterator out of bounds");
         --m_index;
-                --(this->base_reference());
+        --m_it;
     }
 
-            void advance( index_type n )
+    void advance(index_type n)
     {
         m_index += n;
-                BOOST_ASSERT( m_index >= 0 && "Indexed Iterator out of bounds" );
+        BOOST_ASSERT_MSG(m_index >= 0, "indexed Iterator out of bounds");
-                this->base_reference() += n;
+        m_it += n;
     }
-        };
 
-        template< class Rng >
+    difference_type distance_to(const indexed_iterator& other) const
-        struct indexed_range :
-            iterator_range< indexed_iterator<BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type> >
     {
-        private:
+        return other.m_it - m_it;
-            typedef indexed_iterator<BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type>
+    }
-                iter_type;
-            typedef iterator_range<iter_type>
-                base;
-        public:
-            template< class Index >
-            indexed_range( Index i, Rng& r )
-              : base( iter_type(boost::begin(r), i), iter_type(boost::end(r),i) )
-            { }
-        };
 
-    } // 'range_detail'
+    wrapped m_it;
+    index_type m_index;
+};
+
+template<typename SinglePassRange>
+struct indexed_range
+    : iterator_range<
+        indexed_iterator<
+            typename range_iterator<SinglePassRange>::type
+        >
+    >
+{
+    typedef iterator_range<
+        indexed_iterator<
+            typename range_iterator<SinglePassRange>::type
+        >
+    > base_t;
+
+    BOOST_RANGE_CONCEPT_ASSERT((
+        boost::SinglePassRangeConcept<SinglePassRange>));
+public:
+    typedef indexed_iterator<
+        typename range_iterator<SinglePassRange>::type
+    > iterator;
+
+    // Constructor for non-random access iterators.
+    // This sets the end iterator index to i despite this being incorrect it
+    // is never observable since bidirectional iterators are demoted to
+    // forward iterators.
+    indexed_range(
+        typename base_t::difference_type i,
+        SinglePassRange& r,
+        single_pass_traversal_tag
+        )
+        : base_t(iterator(boost::begin(r), i),
+                 iterator(boost::end(r), i))
+    {
+    }
+
+    indexed_range(
+        typename base_t::difference_type i,
+        SinglePassRange& r,
+        random_access_traversal_tag
+        )
+        : base_t(iterator(boost::begin(r), i),
+                 iterator(boost::end(r), i + boost::size(r)))
+    {
+    }
+};
+
+    } // namespace range_detail 
 
-    // Make this available to users of this library. It will sometimes be
-    // required since it is the return type of operator '|' and
-    // index().
     using range_detail::indexed_range;
 
     namespace adaptors
     {
-        template< class SinglePassRange >
+
-        inline indexed_range<SinglePassRange>
+template<class SinglePassRange>
-        operator|( SinglePassRange& r,
+inline indexed_range<SinglePassRange>
-                   const indexed& f )
+operator|(SinglePassRange& r, indexed e)
-        {
+{
     BOOST_RANGE_CONCEPT_ASSERT((
-                    SinglePassRangeConcept<SinglePassRange>));
+        boost::SinglePassRangeConcept<SinglePassRange>
-
+    ));
-            return indexed_range<SinglePassRange>( f.val, r );
+    return indexed_range<SinglePassRange>(
-        }
+                e.val, r,
-
+                typename range_traversal<SinglePassRange>::type());
-        template< class SinglePassRange >
-        inline indexed_range<const SinglePassRange>
-        operator|( const SinglePassRange& r,
-                   const indexed& f )
-        {
-            BOOST_RANGE_CONCEPT_ASSERT((
-                    SinglePassRangeConcept<const SinglePassRange>));
-
-            return indexed_range<const SinglePassRange>( f.val, r );
-        }
-
-        template<class SinglePassRange, class Index>
-        inline indexed_range<SinglePassRange>
-        index(SinglePassRange& rng, Index index_value)
-        {
-            BOOST_RANGE_CONCEPT_ASSERT((
-                    SinglePassRangeConcept<SinglePassRange>));
-
-            return indexed_range<SinglePassRange>(index_value, rng);
-        }
-
-        template<class SinglePassRange, class Index>
-        inline indexed_range<const SinglePassRange>
-        index(const SinglePassRange& rng, Index index_value)
-        {
-            BOOST_RANGE_CONCEPT_ASSERT((
-                    SinglePassRangeConcept<const SinglePassRange>));
-
-            return indexed_range<const SinglePassRange>(index_value, rng);
-        }
-    } // 'adaptors'
-
 }
 
-#ifdef BOOST_MSVC
+template<class SinglePassRange>
-#pragma warning( pop )
+inline indexed_range<const SinglePassRange>
-#endif
+operator|(const SinglePassRange& r, indexed e)
+{
+    BOOST_RANGE_CONCEPT_ASSERT((
+        boost::SinglePassRangeConcept<const SinglePassRange>
+    ));
+    return indexed_range<const SinglePassRange>(
+                e.val, r,
+                typename range_traversal<const SinglePassRange>::type());
+}
 
-#endif
+template<class SinglePassRange>
+inline indexed_range<SinglePassRange>
+index(
+    SinglePassRange& rng,
+    typename range_difference<SinglePassRange>::type index_value = 0)
+{
+    BOOST_RANGE_CONCEPT_ASSERT((
+        boost::SinglePassRangeConcept<SinglePassRange>
+    ));
+    return indexed_range<SinglePassRange>(
+                index_value, rng,
+                typename range_traversal<SinglePassRange>::type());
+}
+
+template<class SinglePassRange>
+inline indexed_range<const SinglePassRange>
+index(
+    const SinglePassRange& rng,
+    typename range_difference<const SinglePassRange>::type index_value = 0)
+{
+    BOOST_RANGE_CONCEPT_ASSERT((
+        boost::SinglePassRangeConcept<SinglePassRange>
+    ));
+    return indexed_range<const SinglePassRange>(
+                index_value, rng,
+                typename range_traversal<const SinglePassRange>::type());
+}
+
+    } // namespace adaptors
+} // namespace boost
+
+#endif // include guard

include/boost/range/traversal.hpp

@@ -0,0 +1,31 @@
+// Boost.Range library
+//
+//  Copyright Neil Groves 2014. Use, modification and
+//  distribution is subject to the Boost Software License, Version
+//  1.0. (See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// For more information, see http://www.boost.org/libs/range/
+//
+
+#ifndef BOOST_RANGE_TRAVERSAL_HPP
+#define BOOST_RANGE_TRAVERSAL_HPP
+
+#if defined(_MSC_VER)
+# pragma once
+#endif
+
+#include <boost/range/config.hpp>
+#include <boost/range/iterator.hpp>
+#include <boost/iterator/iterator_traits.hpp>
+
+namespace boost
+{
+    template<typename SinglePassRange>
+    struct range_traversal
+        : iterator_traversal<typename range_iterator<SinglePassRange>::type>
+    {
+    };
+}
+
+#endif

test/adaptor_test/indexed.cpp

@@ -1,6 +1,6 @@
 // Boost.Range library
 //
-//  Copyright Neil Groves 2009. Use, modification and
+//  Copyright Neil Groves 2014. Use, modification and
 //  distribution is subject to the Boost Software License, Version
 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
 //  http://www.boost.org/LICENSE_1_0.txt)
@@ -14,6 +14,7 @@
 #include <boost/test/unit_test.hpp>
 
 #include <boost/assign.hpp>
+#include <boost/foreach.hpp>
 #include <boost/range/algorithm_ext.hpp>
 #include <boost/range/concepts.hpp>
 
@@ -23,49 +24,61 @@
 
 #include "../test_utils.hpp"
 
-namespace boost
+namespace boost_range_test
 {
     namespace
     {
-        template< class Container >
+
-        void indexed_test_impl( Container& c )
+template<typename Container, typename AdaptedRange>
+void check_result(
+    const Container&    reference_range,
+    const AdaptedRange& adapted_range,
+    std::ptrdiff_t      start_index
+    )
+{
+    typedef typename boost::range_iterator<const Container>::type
+                reference_iterator;
+
+    typedef typename boost::range_iterator<const AdaptedRange>::type
+                adapted_iterator;
+
+    BOOST_REQUIRE_EQUAL(boost::size(reference_range),
+                        boost::size(adapted_range));
+
+    reference_iterator reference_it = boost::begin(reference_range);
+    adapted_iterator adapted_it = boost::begin(adapted_range);
+    for (std::ptrdiff_t i = start_index;
+            reference_it != boost::end(reference_range);
+            ++reference_it, ++adapted_it, ++i)
     {
-            using namespace boost::adaptors;
+        BOOST_CHECK_EQUAL(i, adapted_it->index());
-
+        BOOST_CHECK_EQUAL(*reference_it, adapted_it->value());
-            typedef BOOST_DEDUCED_TYPENAME Container::value_type value_t;
+    }
+}
 
+template<typename Container>
+void indexed_test_impl(Container& c, std::ptrdiff_t start_index)
+{
     // This is my preferred syntax using the | operator.
-            std::vector< value_t > test_result1;
+    check_result(c, c | boost::adaptors::indexed(), 0);
-            boost::push_back(test_result1, c | indexed(0));
+    check_result(c, c | boost::adaptors::indexed(start_index), start_index);
 
-            // This is an alternative syntax preferred by some.
+    // This is the function syntax
-            std::vector< value_t > test_result2;
+    check_result(c, boost::adaptors::index(c), 0);
-            boost::push_back(test_result2, adaptors::index(c, 0));
+    check_result(c, boost::adaptors::index(c, start_index), start_index);
+}
 
-            BOOST_CHECK_EQUAL_COLLECTIONS( c.begin(), c.end(),
+template<typename Container>
-                                           test_result1.begin(), test_result1.end() );
+void indexed_test_impl(Container& c)
+{
+    indexed_test_impl(c, 0);
+    indexed_test_impl(c, -1);
+    indexed_test_impl(c, 4);
+}
 
-            BOOST_CHECK_EQUAL_COLLECTIONS( c.begin(), c.end(),
+template<typename Container>
-                                           test_result2.begin(), test_result2.end() );
+void indexed_test_impl()
-
+{
-            boost::indexed_range< Container > test_result3
-                = c | indexed(0);
-
-            typedef BOOST_DEDUCED_TYPENAME boost::range_const_iterator<
-                boost::indexed_range< Container > >::type iter_t;
-
-            iter_t it = test_result3.begin();
-            for (std::size_t i = 0, count = c.size(); i < count; ++i)
-            {
-                BOOST_CHECK_EQUAL( i, static_cast<std::size_t>(it.index()) );
-                ++it;
-            }
-
-        }
-
-        template< class Container >
-        void indexed_test_impl()
-        {
     using namespace boost::assign;
 
     Container c;
@@ -80,26 +93,60 @@ namespace boost
     // test many elements
     c += 1,2,2,2,3,4,4,4,4,5,6,7,8,9,9;
     indexed_test_impl(c);
-        }
+}
 
-        void indexed_test()
+template<typename Traversal, typename Range>
-        {
+void check_traversal(const Range& rng)
+{
+    BOOST_STATIC_ASSERT(
+        boost::is_convertible<
+            typename boost::range_traversal<const Range>::type,
+            Traversal
+        >::value);
+}
+
+template<typename Traversal, typename Range>
+void check_not_traversal(const Range& rng)
+{
+    BOOST_STATIC_ASSERT(
+        !boost::is_convertible<
+            typename boost::range_traversal<const Range>::type,
+            Traversal
+        >::value);
+}
+
+void indexed_test()
+{
     indexed_test_impl< std::vector< int > >();
     indexed_test_impl< std::list< int > >();
 
-            check_random_access_range_concept(std::vector<int>() | boost::adaptors::indexed(0));
+    std::vector<int> vi;
-            check_bidirectional_range_concept(std::list<int>() | boost::adaptors::indexed(0));
+
-        }
+    check_traversal<boost::random_access_traversal_tag>(
-    }
+        vi | boost::adaptors::indexed());
+
+    std::list<int> li;
+
+    check_traversal<boost::forward_traversal_tag>(
+        li | boost::adaptors::indexed());
+
+    check_not_traversal<boost::bidirectional_traversal_tag>(
+        li | boost::adaptors::indexed());
+
+    check_not_traversal<boost::random_access_traversal_tag>(
+        li | boost::adaptors::indexed());
 }
 
+    } // anonymous namesapce
+} // namespace boost_range_test
+
 boost::unit_test::test_suite*
-init_unit_test_suite(int argc, char* argv[])
+init_unit_test_suite(int, char*[])
 {
     boost::unit_test::test_suite* test
-        = BOOST_TEST_SUITE( "RangeTestSuite.adaptor.indexed" );
+        = BOOST_TEST_SUITE( "Boost.Range indexed adaptor test suite" );
 
-    test->add( BOOST_TEST_CASE( &boost::indexed_test ) );
+    test->add(BOOST_TEST_CASE(&boost_range_test::indexed_test));
 
     return test;
 }

test/adaptor_test/indexed_example.cpp

@@ -9,8 +9,12 @@
 // For more information, see http://www.boost.org/libs/range/
 //
 //[indexed_example
+
+//<-
+#include <boost/config.hpp>
+//->
+
 #include <boost/range/adaptor/indexed.hpp>
-#include <boost/range/algorithm/copy.hpp>
 #include <boost/assign.hpp>
 #include <iterator>
 #include <iostream>
@@ -20,8 +24,6 @@
 #include <boost/test/test_tools.hpp>
 #include <boost/test/unit_test.hpp>
 
-#include <boost/range/algorithm_ext/push_back.hpp>
-
 namespace 
 {
 
@@ -35,14 +37,14 @@ void check_element_and_index(
     BOOST_CHECK_EQUAL( std::distance(test_first, test_last),
                        std::distance(reference_first, reference_last) );
 
-    int reference_index = 0;
+    std::ptrdiff_t reference_index = 0;
 
     Iterator1 test_it = test_first;
     Iterator2 reference_it = reference_first;
     for (; test_it != test_last; ++test_it, ++reference_it, ++reference_index)
     {
-        BOOST_CHECK_EQUAL( *test_it, *reference_it );
+        BOOST_CHECK_EQUAL(test_it->value(), *reference_it);
-        BOOST_CHECK_EQUAL( test_it.index(), reference_index );
+        BOOST_CHECK_EQUAL(test_it->index(), reference_index);
     }
 }
 
@@ -51,24 +53,11 @@ void check_element_and_index(
     const SinglePassRange1& test_rng,
     const SinglePassRange2& reference_rng)
 {
-    check_element_and_index(boost::begin(test_rng), boost::end(test_rng),
+    check_element_and_index(
+        boost::begin(test_rng), boost::end(test_rng),
         boost::begin(reference_rng), boost::end(reference_rng));
 }
 //->
-template<class Iterator>
-void display_element_and_index(Iterator first, Iterator last)
-{
-    for (Iterator it = first; it != last; ++it)
-    {
-        std::cout << "Element = " << *it << " Index = " << it.index() << std::endl;
-    }
-}
-
-template<class SinglePassRange>
-void display_element_and_index(const SinglePassRange& rng)
-{
-    display_element_and_index(boost::begin(rng), boost::end(rng));
-}
 
 //<-
 void indexed_example_test()
@@ -81,7 +70,18 @@ void indexed_example_test()
     std::vector<int> input;
     input += 10,20,30,40,50,60,70,80,90;
 
-    display_element_and_index( input | indexed(0) );
+//<-
+#ifndef BOOST_NO_CXX11_RANGE_BASED_FOR
+//->
+    for (const auto& element : input | indexed(0))
+    {
+        std::cout << "Element = " << element.value()
+                  << " Index = " << element.index()
+                  << std::endl;
+    }
+//<-
+#endif // C++11 has range for loop
+//->
     
 //=    return 0;
 //=}