text: // Boost.Geometry (aka GGL, Generic Geometry Library)
  
  // Copyright (c) 2007-2011 Barend Gehrels, Amsterdam, the Netherlands.
  // Copyright (c) 2008-2011 Bruno Lalande, Paris, France.
  // Copyright (c) 2009-2011 Mateusz Loskot, London, UK.
  
  // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
  // (geolib/GGL), copyright (c) 1995-2010 Geodan, 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_ALGORITHMS_CLEAR_HPP
  #define BOOST_GEOMETRY_ALGORITHMS_CLEAR_HPP
  
  #include <boost/mpl/assert.hpp>
  #include <boost/type_traits/remove_const.hpp>
  
  #include <boost/geometry/core/access.hpp>
  #include <boost/geometry/core/exterior_ring.hpp>
  #include <boost/geometry/core/interior_rings.hpp>
  #include <boost/geometry/core/mutable_range.hpp>
  #include <boost/geometry/core/tag_cast.hpp>
  
  #include <boost/geometry/geometries/concepts/check.hpp>
  
  
  namespace boost { namespace geometry
  {
  
  #ifndef DOXYGEN_NO_DETAIL
  namespace detail { namespace clear
  {
  
  template <typename Geometry>
  struct collection_clear
  {
      static inline void apply(Geometry& geometry)
      {
          traits::clear<Geometry>::apply(geometry);
      }
  };
  
  template <typename Polygon>
  struct polygon_clear
  {
      static inline void apply(Polygon& polygon)
      {
          traits::clear
              <
                  typename boost::remove_reference
                      <
                          typename traits::interior_mutable_type<Polygon>::type
                      >::type
              >::apply(interior_rings(polygon));
          traits::clear
              <
                  typename boost::remove_reference
                      <
                          typename traits::ring_mutable_type<Polygon>::type
                      >::type
              >::apply(exterior_ring(polygon));
      }
  };
  
  template <typename Geometry>
  struct no_action
  {
      static inline void apply(Geometry& )
      {
      }
  };
  
  }} // namespace detail::clear
  #endif // DOXYGEN_NO_DETAIL
  
  #ifndef DOXYGEN_NO_DISPATCH
  namespace dispatch
  {
  
  template <typename Tag, typename Geometry>
  struct clear
  {
      BOOST_MPL_ASSERT_MSG
          (
              false, NOT_OR_NOT_YET_IMPLEMENTED_FOR_THIS_GEOMETRY_TYPE
              , (types<Geometry>)
          );
  };
  
  // Point/box/segment do not have clear. So specialize to do nothing.
  template <typename Geometry>
  struct clear<point_tag, Geometry>
      : detail::clear::no_action<Geometry>
  {};
  
  template <typename Geometry>
  struct clear<box_tag, Geometry>
      : detail::clear::no_action<Geometry>
  {};
  
  template <typename Geometry>
  struct clear<segment_tag, Geometry>
      : detail::clear::no_action<Geometry>
  {};
  
  template <typename Geometry>
  struct clear<linestring_tag, Geometry>
      : detail::clear::collection_clear<Geometry>
  {};
  
  template <typename Geometry>
  struct clear<ring_tag, Geometry>
      : detail::clear::collection_clear<Geometry>
  {};
  
  
  // Polygon can (indirectly) use std for clear
  template <typename Polygon>
  struct clear<polygon_tag, Polygon>
      : detail::clear::polygon_clear<Polygon>
  {};
  
  
  } // namespace dispatch
  #endif // DOXYGEN_NO_DISPATCH
  
  
  /*!
  \brief Clears a linestring, ring or polygon (exterior+interiors) or multi*
  \details Generic function to clear a geometry. All points will be removed from the collection or collections
      making up the geometry. In most cases this is equivalent to the .clear() method of a std::vector<...>. In
      the case of a polygon, this clear functionality is automatically called for the exterior ring, and for the
      interior ring collection. In the case of a point, boxes and segments, nothing will happen.
  \ingroup clear
  \tparam Geometry \tparam_geometry
  \param geometry \param_geometry which will be cleared
  \note points and boxes cannot be cleared, instead they can be set to zero by "assign_zero"
  
  \qbk{[include reference/algorithms/clear.qbk]}
  */
  template <typename Geometry>
  inline void clear(Geometry& geometry)
  {
      concept::check<Geometry>();
  
      dispatch::clear
          <
              typename tag_cast<typename tag<Geometry>::type, multi_tag>::type,
              Geometry
          >::apply(geometry);
  }
  
  
  }} // namespace boost::geometry
  
  
  #endif // BOOST_GEOMETRY_ALGORITHMS_CLEAR_HPP
  