288 lines
7.3 KiB
C++
288 lines
7.3 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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// Copyright (c) 2007-2011 Barend Gehrels, Amsterdam, the Netherlands.
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// Copyright (c) 2008-2011 Bruno Lalande, Paris, France.
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// Copyright (c) 2009-2011 Mateusz Loskot, London, UK.
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// Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
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// (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
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// Use, modification and distribution is subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_GEOMETRY_ALGORITHMS_AREA_HPP
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#define BOOST_GEOMETRY_ALGORITHMS_AREA_HPP
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#include <boost/concept_check.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/range/functions.hpp>
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#include <boost/range/metafunctions.hpp>
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#include <boost/geometry/core/closure.hpp>
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#include <boost/geometry/core/exterior_ring.hpp>
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#include <boost/geometry/core/interior_rings.hpp>
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#include <boost/geometry/core/point_order.hpp>
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#include <boost/geometry/core/ring_type.hpp>
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#include <boost/geometry/geometries/concepts/check.hpp>
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#include <boost/geometry/algorithms/detail/calculate_null.hpp>
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#include <boost/geometry/algorithms/detail/calculate_sum.hpp>
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#include <boost/geometry/strategies/area.hpp>
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#include <boost/geometry/strategies/default_area_result.hpp>
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#include <boost/geometry/strategies/concepts/area_concept.hpp>
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#include <boost/geometry/util/math.hpp>
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#include <boost/geometry/util/order_as_direction.hpp>
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#include <boost/geometry/views/closeable_view.hpp>
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#include <boost/geometry/views/reversible_view.hpp>
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namespace boost { namespace geometry
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{
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#ifndef DOXYGEN_NO_DETAIL
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namespace detail { namespace area
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{
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template<typename Box, typename Strategy>
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struct box_area
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{
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typedef typename coordinate_type<Box>::type return_type;
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static inline return_type apply(Box const& box, Strategy const&)
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{
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// Currently only works for 2D Cartesian boxes
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assert_dimension<Box, 2>();
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return_type const dx = get<max_corner, 0>(box)
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- get<min_corner, 0>(box);
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return_type const dy = get<max_corner, 1>(box)
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- get<min_corner, 1>(box);
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return dx * dy;
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}
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};
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template
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<
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typename Ring,
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iterate_direction Direction,
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closure_selector Closure,
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typename Strategy
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>
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struct ring_area
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{
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BOOST_CONCEPT_ASSERT( (geometry::concept::AreaStrategy<Strategy>) );
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typedef typename Strategy::return_type type;
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static inline type apply(Ring const& ring, Strategy const& strategy)
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{
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assert_dimension<Ring, 2>();
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// Ignore warning (because using static method sometimes) on strategy
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boost::ignore_unused_variable_warning(strategy);
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// An open ring has at least three points,
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// A closed ring has at least four points,
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// if not, there is no (zero) area
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if (boost::size(ring)
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< core_detail::closure::minimum_ring_size<Closure>::value)
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{
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return type();
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}
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typedef typename reversible_view<Ring const, Direction>::type rview_type;
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typedef typename closeable_view
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<
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rview_type const, Closure
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>::type view_type;
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typedef typename boost::range_iterator<view_type const>::type iterator_type;
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rview_type rview(ring);
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view_type view(rview);
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typename Strategy::state_type state;
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iterator_type it = boost::begin(view);
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iterator_type end = boost::end(view);
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for (iterator_type previous = it++;
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it != end;
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++previous, ++it)
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{
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strategy.apply(*previous, *it, state);
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}
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return strategy.result(state);
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}
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};
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}} // namespace detail::area
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#endif // DOXYGEN_NO_DETAIL
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#ifndef DOXYGEN_NO_DISPATCH
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namespace dispatch
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{
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template
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<
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typename Tag,
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typename Geometry,
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typename Strategy
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>
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struct area
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: detail::calculate_null
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<
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typename Strategy::return_type,
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Geometry,
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Strategy
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> {};
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template
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<
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typename Geometry,
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typename Strategy
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>
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struct area<box_tag, Geometry, Strategy>
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: detail::area::box_area<Geometry, Strategy>
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{};
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template
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<
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typename Ring,
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typename Strategy
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>
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struct area<ring_tag, Ring, Strategy>
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: detail::area::ring_area
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<
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Ring,
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order_as_direction<geometry::point_order<Ring>::value>::value,
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geometry::closure<Ring>::value,
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Strategy
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>
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{};
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template
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<
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typename Polygon,
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typename Strategy
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>
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struct area<polygon_tag, Polygon, Strategy>
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: detail::calculate_polygon_sum
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<
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typename Strategy::return_type,
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Polygon,
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Strategy,
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detail::area::ring_area
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<
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typename ring_type<Polygon const>::type,
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order_as_direction<geometry::point_order<Polygon>::value>::value,
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geometry::closure<Polygon>::value,
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Strategy
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>
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>
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{};
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} // namespace dispatch
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#endif // DOXYGEN_NO_DISPATCH
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/*!
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\brief \brief_calc{area}
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\ingroup area
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\details \details_calc{area}. \details_default_strategy
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The area algorithm calculates the surface area of all geometries having a surface, namely
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box, polygon, ring, multipolygon. The units are the square of the units used for the points
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defining the surface. If subject geometry is defined in meters, then area is calculated
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in square meters.
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The area calculation can be done in all three common coordinate systems, Cartesian, Spherical
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and Geographic as well.
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\tparam Geometry \tparam_geometry
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\param geometry \param_geometry
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\return \return_calc{area}
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\qbk{[include reference/algorithms/area.qbk]}
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\qbk{[heading Examples]}
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\qbk{[area] [area_output]}
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*/
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template <typename Geometry>
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inline typename default_area_result<Geometry>::type area(Geometry const& geometry)
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{
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concept::check<Geometry const>();
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typedef typename point_type<Geometry>::type point_type;
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typedef typename strategy::area::services::default_strategy
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<
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typename cs_tag<point_type>::type,
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point_type
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>::type strategy_type;
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return dispatch::area
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<
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typename tag<Geometry>::type,
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Geometry,
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strategy_type
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>::apply(geometry, strategy_type());
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}
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/*!
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\brief \brief_calc{area} \brief_strategy
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\ingroup area
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\details \details_calc{area} \brief_strategy. \details_strategy_reasons
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\tparam Geometry \tparam_geometry
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\tparam Strategy \tparam_strategy{Area}
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\param geometry \param_geometry
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\param strategy \param_strategy{area}
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\return \return_calc{area}
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\qbk{distinguish,with strategy}
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\qbk{
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[include reference/algorithms/area.qbk]
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[heading Example]
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[area_with_strategy]
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[area_with_strategy_output]
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[heading Available Strategies]
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\* [link geometry.reference.strategies.strategy_area_surveyor Surveyor (cartesian)]
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\* [link geometry.reference.strategies.strategy_area_huiller Huiller (spherical)]
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}
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*/
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template <typename Geometry, typename Strategy>
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inline typename Strategy::return_type area(
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Geometry const& geometry, Strategy const& strategy)
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{
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concept::check<Geometry const>();
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return dispatch::area
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<
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typename tag<Geometry>::type,
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Geometry,
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Strategy
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>::apply(geometry, strategy);
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}
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_ALGORITHMS_AREA_HPP
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