text: // Boost.Geometry (aka GGL, Generic Geometry Library)
  
  // Copyright (c) 2007-2014 Barend Gehrels, Amsterdam, the Netherlands.
  
  // This file was modified by Oracle on 2014.
  // Modifications copyright (c) 2014 Oracle and/or its affiliates.
  
  // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
  
  // 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_UNION_HPP
  #define BOOST_GEOMETRY_ALGORITHMS_UNION_HPP
  
  
  #include <boost/range/metafunctions.hpp>
  
  #include <boost/geometry/core/is_areal.hpp>
  #include <boost/geometry/core/point_order.hpp>
  #include <boost/geometry/core/reverse_dispatch.hpp>
  #include <boost/geometry/geometries/concepts/check.hpp>
  #include <boost/geometry/algorithms/not_implemented.hpp>
  #include <boost/geometry/algorithms/detail/overlay/overlay.hpp>
  #include <boost/geometry/policies/robustness/get_rescale_policy.hpp>
  
  #include <boost/geometry/algorithms/detail/overlay/linear_linear.hpp>
  #include <boost/geometry/algorithms/detail/overlay/pointlike_pointlike.hpp>
  
  
  namespace boost { namespace geometry
  {
  
  #ifndef DOXYGEN_NO_DISPATCH
  namespace dispatch
  {
  
  template
  <
      typename Geometry1, typename Geometry2, typename GeometryOut,
      typename TagIn1 = typename tag<Geometry1>::type,
      typename TagIn2 = typename tag<Geometry2>::type,
      typename TagOut = typename tag<GeometryOut>::type,
      bool Areal1 = geometry::is_areal<Geometry1>::value,
      bool Areal2 = geometry::is_areal<Geometry2>::value,
      bool ArealOut = geometry::is_areal<GeometryOut>::value,
      bool Reverse1 = detail::overlay::do_reverse<geometry::point_order<Geometry1>::value>::value,
      bool Reverse2 = detail::overlay::do_reverse<geometry::point_order<Geometry2>::value>::value,
      bool ReverseOut = detail::overlay::do_reverse<geometry::point_order<GeometryOut>::value>::value,
      bool Reverse = geometry::reverse_dispatch<Geometry1, Geometry2>::type::value
  >
  struct union_insert: not_implemented<TagIn1, TagIn2, TagOut>
  {};
  
  
  // If reversal is needed, perform it first
  
  template
  <
      typename Geometry1, typename Geometry2, typename GeometryOut,
      typename TagIn1, typename TagIn2, typename TagOut,
      bool Areal1, bool Areal2, bool ArealOut,
      bool Reverse1, bool Reverse2, bool ReverseOut
  >
  struct union_insert
      <
          Geometry1, Geometry2, GeometryOut,
          TagIn1, TagIn2, TagOut,
          Areal1, Areal2, ArealOut,
          Reverse1, Reverse2, ReverseOut,
          true
      >: union_insert<Geometry2, Geometry1, GeometryOut>
  {
      template <typename RobustPolicy, typename OutputIterator, typename Strategy>
      static inline OutputIterator apply(Geometry1 const& g1,
              Geometry2 const& g2,
              RobustPolicy const& robust_policy,
              OutputIterator out,
              Strategy const& strategy)
      {
          return union_insert
              <
                  Geometry2, Geometry1, GeometryOut
              >::apply(g2, g1, robust_policy, out, strategy);
      }
  };
  
  
  template
  <
      typename Geometry1, typename Geometry2, typename GeometryOut,
      typename TagIn1, typename TagIn2, typename TagOut,
      bool Reverse1, bool Reverse2, bool ReverseOut
  >
  struct union_insert
      <
          Geometry1, Geometry2, GeometryOut,
          TagIn1, TagIn2, TagOut,
          true, true, true,
          Reverse1, Reverse2, ReverseOut,
          false
      > : detail::overlay::overlay
          <Geometry1, Geometry2, Reverse1, Reverse2, ReverseOut, GeometryOut, overlay_union>
  {};
  
  
  // dispatch for union of non-areal geometries
  template
  <
      typename Geometry1, typename Geometry2, typename GeometryOut,
      typename TagIn1, typename TagIn2, typename TagOut,
      bool Reverse1, bool Reverse2, bool ReverseOut
  >
  struct union_insert
      <
          Geometry1, Geometry2, GeometryOut,
          TagIn1, TagIn2, TagOut,
          false, false, false,
          Reverse1, Reverse2, ReverseOut,
          false
      > : union_insert
          <
              Geometry1, Geometry2, GeometryOut,
              typename tag_cast<TagIn1, pointlike_tag, linear_tag>::type,
              typename tag_cast<TagIn2, pointlike_tag, linear_tag>::type,
              TagOut,
              false, false, false,
              Reverse1, Reverse2, ReverseOut,
              false
          >
  {};
  
  
  // dispatch for union of linear geometries
  template
  <
      typename Linear1, typename Linear2, typename LineStringOut,
      bool Reverse1, bool Reverse2, bool ReverseOut
  >
  struct union_insert
      <
          Linear1, Linear2, LineStringOut,
          linear_tag, linear_tag, linestring_tag,
          false, false, false,
          Reverse1, Reverse2, ReverseOut,
          false
      > : detail::overlay::linear_linear_linestring
          <
              Linear1, Linear2, LineStringOut, overlay_union
          >
  {};
  
  
  // dispatch for point-like geometries
  template
  <
      typename PointLike1, typename PointLike2, typename PointOut,
      bool Reverse1, bool Reverse2, bool ReverseOut
  >
  struct union_insert
      <
          PointLike1, PointLike2, PointOut,
          pointlike_tag, pointlike_tag, point_tag,
          false, false, false,
          Reverse1, Reverse2, ReverseOut,
          false
      > : detail::overlay::union_pointlike_pointlike_point
          <
              PointLike1, PointLike2, PointOut
          >
  {};
  
  
  } // namespace dispatch
  #endif // DOXYGEN_NO_DISPATCH
  
  #ifndef DOXYGEN_NO_DETAIL
  namespace detail { namespace union_
  {
  
  /*!
  \brief_calc2{union}
  \ingroup union
  \details \details_calc2{union_insert, spatial set theoretic union}.
      \details_insert{union}
  \tparam GeometryOut output geometry type, must be specified
  \tparam Geometry1 \tparam_geometry
  \tparam Geometry2 \tparam_geometry
  \tparam OutputIterator output iterator
  \param geometry1 \param_geometry
  \param geometry2 \param_geometry
  \param out \param_out{union}
  \return \return_out
  */
  template
  <
      typename GeometryOut,
      typename Geometry1,
      typename Geometry2,
      typename OutputIterator
  >
  inline OutputIterator union_insert(Geometry1 const& geometry1,
              Geometry2 const& geometry2,
              OutputIterator out)
  {
      concepts::check<Geometry1 const>();
      concepts::check<Geometry2 const>();
      concepts::check<GeometryOut>();
  
      typedef typename geometry::rescale_overlay_policy_type
          <
              Geometry1,
              Geometry2
          >::type rescale_policy_type;
  
      typedef intersection_strategies
          <
              typename cs_tag<GeometryOut>::type,
              Geometry1,
              Geometry2,
              typename geometry::point_type<GeometryOut>::type,
              rescale_policy_type
          > strategy;
  
      rescale_policy_type robust_policy
              = geometry::get_rescale_policy<rescale_policy_type>(geometry1, geometry2);
  
      return dispatch::union_insert
             <
                 Geometry1, Geometry2, GeometryOut
             >::apply(geometry1, geometry2, robust_policy, out, strategy());
  }
  
  
  }} // namespace detail::union_
  #endif // DOXYGEN_NO_DETAIL
  
  
  
  
  /*!
  \brief Combines two geometries which each other
  \ingroup union
  \details \details_calc2{union, spatial set theoretic union}.
  \tparam Geometry1 \tparam_geometry
  \tparam Geometry2 \tparam_geometry
  \tparam Collection output collection, either a multi-geometry,
      or a std::vector<Geometry> / std::deque<Geometry> etc
  \param geometry1 \param_geometry
  \param geometry2 \param_geometry
  \param output_collection the output collection
  \note Called union_ because union is a reserved word.
  
  \qbk{[include reference/algorithms/union.qbk]}
  */
  template
  <
      typename Geometry1,
      typename Geometry2,
      typename Collection
  >
  inline void union_(Geometry1 const& geometry1,
              Geometry2 const& geometry2,
              Collection& output_collection)
  {
      concepts::check<Geometry1 const>();
      concepts::check<Geometry2 const>();
  
      typedef typename boost::range_value<Collection>::type geometry_out;
      concepts::check<geometry_out>();
  
      detail::union_::union_insert<geometry_out>(geometry1, geometry2,
                  range::back_inserter(output_collection));
  }
  
  
  }} // namespace boost::geometry
  
  
  #endif // BOOST_GEOMETRY_ALGORITHMS_UNION_HPP
  