Boost.RangeEx merged into Boost.Range

[SVN r60897]

include/boost/range/irange.hpp

@@ -0,0 +1,202 @@
+// Boost.Range library
+//
+//  Copyright Neil Groves 2010. 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_IRANGE_HPP_INCLUDED
+#define BOOST_RANGE_IRANGE_HPP_INCLUDED
+
+#include <boost/assert.hpp>
+#include <boost/iterator/iterator_facade.hpp>
+#include <boost/range/iterator_range.hpp>
+
+namespace boost
+{
+    namespace range_detail
+    {
+        // integer_iterator is an iterator over an integer sequence that
+        // is bounded only by the limits of the underlying integer
+        // representation.
+        //
+        // This is useful for implementing the irange(first, last)
+        // function.
+        //
+        // Note:
+        // This use of this iterator and irange is appreciably less
+        // performant than the corresponding hand-written integer
+        // loop on many compilers.
+        template<typename Integer>
+        class integer_iterator
+            : public boost::iterator_facade<
+                        integer_iterator<Integer>,
+                        Integer,
+                        boost::random_access_traversal_tag,
+                        const Integer&
+                    >
+        {
+            typedef boost::iterator_facade<
+                        integer_iterator<Integer>,
+                        Integer,
+                        boost::random_access_traversal_tag,
+                        const Integer&
+                    > base_t;
+        public:
+            typedef typename base_t::value_type value_type;
+            typedef typename base_t::difference_type difference_type;
+            typedef typename base_t::reference reference;
+
+            integer_iterator() : m_value() {}
+            explicit integer_iterator(value_type x) : m_value(x) {}
+
+        private:
+            void increment()
+            {
+                ++m_value;
+            }
+
+            void decrement()
+            {
+                --m_value;
+            }
+
+            void advance(difference_type offset)
+            {
+                m_value += offset;
+            }
+
+            difference_type distance_to(const integer_iterator& other) const
+            {
+                return other.m_value - m_value;
+            }
+
+            bool equal(const integer_iterator& other) const
+            {
+                return m_value == other.m_value;
+            }
+
+            reference dereference() const
+            {
+                return m_value;
+            }
+
+            friend class ::boost::iterator_core_access;
+            value_type m_value;
+        };
+
+        // integer_iterator_with_step is similar in nature to the
+        // integer_iterator but provides the ability to 'move' in
+        // a number of steps specified at construction time.
+        //
+        // The three variable implementation provides the best guarantees
+        // of loop termination upon various combinations of input.
+        //
+        // While this design is less performant than some less
+        // safe alternatives, the use of ranges and iterators to
+        // perform counting will never be optimal anyhow, hence
+        // if optimal performance is desired a handcoded loop
+        // is the solution.
+        template<typename Integer>
+        class integer_iterator_with_step
+            : public boost::iterator_facade<
+                        integer_iterator_with_step<Integer>,
+                        Integer,
+                        boost::random_access_traversal_tag,
+                        Integer,
+                        std::ptrdiff_t
+                    >
+        {
+            typedef boost::iterator_facade<
+                        integer_iterator_with_step<Integer>,
+                        Integer,
+                        boost::random_access_traversal_tag,
+                        Integer,
+                        std::ptrdiff_t
+                    > base_t;
+        public:
+            typedef typename base_t::value_type value_type;
+            typedef typename base_t::difference_type difference_type;
+            typedef typename base_t::reference reference;
+
+            integer_iterator_with_step(value_type first, value_type step, difference_type step_size)
+                : m_first(first)
+                , m_step(step)
+                , m_step_size(step_size)
+            {
+                BOOST_ASSERT( step >= 0 );
+                BOOST_ASSERT( step_size != 0 );
+            }
+
+        private:
+            void increment()
+            {
+                ++m_step;
+            }
+
+            void decrement()
+            {
+                --m_step;
+            }
+
+            void advance(difference_type offset)
+            {
+                m_step += offset;
+            }
+
+            difference_type distance_to(const integer_iterator_with_step& other) const
+            {
+                return other.m_step - m_step;
+            }
+
+            bool equal(const integer_iterator_with_step& other) const
+            {
+                return m_step == other.m_step;
+            }
+
+            reference dereference() const
+            {
+                return m_first + (m_step * m_step_size);
+            }
+
+            friend class ::boost::iterator_core_access;
+            value_type m_first;
+            value_type m_step;
+            difference_type m_step_size;
+        };
+
+    } // namespace range_detail
+
+    template<typename Integer>
+    iterator_range< range_detail::integer_iterator<Integer> >
+        irange(Integer first, Integer last)
+    {
+        BOOST_ASSERT( first <= last );
+        return boost::iterator_range< range_detail::integer_iterator<Integer> >(
+                range_detail::integer_iterator<Integer>(first),
+                range_detail::integer_iterator<Integer>(last));
+    }
+
+    template<typename Integer, typename StepSize>
+    iterator_range< range_detail::integer_iterator_with_step<Integer> >
+        irange(Integer first, Integer last, StepSize step_size)
+    {
+        BOOST_ASSERT( step_size != 0 );
+        BOOST_ASSERT( (step_size > 0) ? (last >= first) : (last <= first) );
+        typedef typename range_detail::integer_iterator_with_step<Integer> iterator_t;
+
+        const std::ptrdiff_t last_step
+            = (static_cast<std::ptrdiff_t>(last) - static_cast<std::ptrdiff_t>(first))
+            / (static_cast<std::ptrdiff_t>(step_size));
+
+        return boost::iterator_range< iterator_t >(
+            iterator_t(first, 0, step_size),
+            iterator_t(first, last_step, step_size));
+    }
+
+} // namespace boost
+
+#endif // include guard