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A ring (aka linear ring) is a closed line which should not be selfintersecting.
template<typename Point, bool ClockWise, bool Closed, template< typename, typename > class Container, template< typename > class Allocator> class model::ring : public Container< Point, Allocator< Point > > { // ... };
| Parameter | Default | Description | 
|---|---|---|
| typename Point | point type | |
| bool ClockWise | true | true for clockwise direction, false for CounterClockWise direction | 
| bool Closed | true | true for closed polygons (last point == first point), false open points | 
| template< typename, typename > class Container | std::vector | container type, for example std::vector, std::deque | 
| template< typename > class Allocator | std::allocator | container-allocator-type | 
| Function | Description | Parameters | 
|---|---|---|
| 
 ring() 
 | Default constructor, creating an empty ring. | |
| 
 template<typename Iterator> ring(Iterator begin, Iterator end) 
 | Constructor with begin and end, filling the ring. | Iterator: begin: Iterator: end: | 
| 
 ring(std::initializer_list< Point > l) 
 | Constructor taking std::initializer_list, filling the ring. | std::initializer_list< Point >: l: | 
Either
          #include <boost/geometry/geometries/geometries.hpp>
        
Or
          #include <boost/geometry/geometries/ring.hpp>
        
Declaration and use of the Boost.Geometry model::ring, modelling the Ring Concept
#include <iostream> #include <boost/geometry.hpp> #include <boost/geometry/geometries/geometries.hpp> namespace bg = boost::geometry; int main() { typedef bg::model::point<double, 2, bg::cs::cartesian> point_t; typedef bg::model::ring<point_t> ring_t;ring_t ring1;
#if !defined(BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX) \ && !defined(BOOST_NO_CXX11_HDR_INITIALIZER_LIST) ring_t ring2{{0.0, 0.0}, {0.0, 5.0}, {5.0, 5.0}, {5.0, 0.0}, {0.0, 0.0}};
#endif bg::append(ring1, point_t(0.0, 0.0));
bg::append(ring1, point_t(0.0, 5.0)); bg::append(ring1, point_t(5.0, 5.0)); bg::append(ring1, point_t(5.0, 0.0)); bg::append(ring1, point_t(0.0, 0.0)); double a = bg::area(ring1); std::cout << a << std::endl; return 0; }
| Default parameters, clockwise, closed ring. | |
| Default-construct a ring. | |
| Construct a ring containing four points plus one closing point, using C++11 unified initialization syntax. | |
| Append point. | 
Output:
25