...one of the most highly
regarded and expertly designed C++ library projects in the
world.

— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards

Metafunction defining **value** as the point
order (clockwise, counterclockwise) of the \3.

template<typename Geometry> struct point_order { // ... };

Parameter |
Description |
---|---|

typename Geometry |
Any type fulfilling a Geometry Concept |

Either

`#include <boost/geometry.hpp>`

Or

`#include <boost/geometry/core/point_order.hpp>`

Note | |
---|---|

The point order is defined for any geometry type, but only has a real meaning for areal geometry types (ring, polygon, multi_polygon) |

Compile time

Examine the expected point order of a polygon type

#include <iostream> #include <boost/geometry.hpp> #include <boost/geometry/geometries/polygon.hpp> #include <boost/geometry/geometries/point_xy.hpp> int main() { typedef boost::geometry::model::d2::point_xy<double> point_type; typedef boost::geometry::model::polygon<point_type, false> polygon_type; boost::geometry::order_selector order = boost::geometry::point_order<polygon_type>::value; std::cout << "order: " << order << std::endl << "(clockwise = " << boost::geometry::clockwise << ", counterclockwise = " << boost::geometry::counterclockwise << ") "<< std::endl; return 0; }

Output:

order: 2 (clockwise = 1, counterclockwise = 2)