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+// Boost.Geometry (aka GGL, Generic Geometry Library)
+
+// Copyright (c) 2012-2014 Barend Gehrels, Amsterdam, the Netherlands.
+
+// 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)
+
+#ifndef BOOST_GEOMETRY_STRATEGIES_AGNOSTIC_BUFFER_DISTANCE_SYMMETRIC_HPP
+#define BOOST_GEOMETRY_STRATEGIES_AGNOSTIC_BUFFER_DISTANCE_SYMMETRIC_HPP
+
+#include <boost/geometry/strategies/buffer.hpp>
+#include <boost/geometry/util/math.hpp>
+
+
+namespace boost { namespace geometry
+{
+
+namespace strategy { namespace buffer
+{
+
+
+/*!
+\brief Let the buffer algorithm create buffers with same distances
+\ingroup strategies
+\tparam NumericType \tparam_numeric
+\details This strategy can be used as DistanceStrategy for the buffer algorithm.
+    It can be applied for all geometries. It uses one distance for left and
+    for right.
+    If the distance is negative and used with a (multi)polygon or ring, the
+    geometry will shrink (deflate) instead of expand (inflate).
+
+\qbk{
+[heading Example]
+[buffer_distance_symmetric]
+[heading Output]
+[$img/strategies/buffer_distance_symmetric.png]
+[heading See also]
+\* [link geometry.reference.algorithms.buffer.buffer_7_with_strategies buffer (with strategies)]
+\* [link geometry.reference.strategies.strategy_buffer_distance_asymmetric distance_asymmetric]
+}
+ */
+template<typename NumericType>
+class distance_symmetric
+{
+public :
+    //! \brief Constructs the strategy, a distance must be specified
+    //! \param distance The distance (or radius) of the buffer
+    explicit inline distance_symmetric(NumericType const& distance)
+        : m_distance(distance)
+    {}
+
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
+    //! Returns the distance-value
+    template <typename Point>
+    inline NumericType apply(Point const& , Point const& ,
+                buffer_side_selector )  const
+    {
+        return negative() ? geometry::math::abs(m_distance) : m_distance;
+    }
+
+    //! Used internally, returns -1 for deflate, 1 for inflate
+    inline int factor() const
+    {
+        return negative() ? -1 : 1;
+    }
+
+    //! Returns true if distance is negative
+    inline bool negative() const
+    {
+        return m_distance < 0;
+    }
+
+    //! Returns the max distance distance up to the buffer will reach
+    template <typename JoinStrategy, typename EndStrategy>
+    inline NumericType max_distance(JoinStrategy const& join_strategy,
+            EndStrategy const& end_strategy) const
+    {
+        NumericType const dist = geometry::math::abs(m_distance);
+        return (std::max)(join_strategy.max_distance(dist),
+                          end_strategy.max_distance(dist));
+    }
+
+
+    //! Returns the distance at which the input is simplified before the buffer process
+    inline NumericType simplify_distance() const
+    {
+        return geometry::math::abs(m_distance) / 1000.0;
+    }
+#endif // DOXYGEN_SHOULD_SKIP_THIS
+
+private :
+    NumericType m_distance;
+};
+
+
+}} // namespace strategy::buffer
+
+
+}} // namespace boost::geometry
+
+#endif // BOOST_GEOMETRY_STRATEGIES_AGNOSTIC_BUFFER_DISTANCE_SYMMETRIC_HPP