[/============================================================================
  Boost.Geometry (aka GGL, Generic Geometry Library)

  Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
  Copyright (c) 2009-2012 Barend Gehrels, Amsterdam, the Netherlands.
  Copyright (c) 2009-2012 Bruno Lalande, Paris, France.

  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)
=============================================================================/]

[section:concept_ring Ring Concept]

[heading Description]
[concept Ring..ring]

[note Also called linear ring, but we explicitly refer to a filled feature here]

[heading Concept Definition]

The Ring Concept is defined as following:

* there must be a specialization of `traits::tag` defining `ring_tag` as type
* it must behave like a Boost.Range Random Access Range
* The type defined by the metafunction `range_value<...>::type` must fulfill 
	the [link geometry.reference.concepts.concept_point Point Concept]
* there might be a specialization of `traits::point_order` defining the order or orientation of its points, `clockwise` or `counterclockwise`
* there might be a specialization of `traits::closure` defining the closure, `open` or `closed`

[heading Rules]

Besides the Concepts, which are checks on compile-time, there are
rules that valid rings must fulfill. See the
[link geometry.reference.concepts.concept_polygon Polygon Concept] for more information
on the rules a polygon (and also a ring) must fulfill.

[heading Available Models]	
* [link geometry.reference.models.model_ring ring]
* a Boost.Polygon polygon_data (requires `#include boost/geometry/geometries/adapted/boost_polygon/ring.hpp>`)

[see_boost_range_sample Ring]

[endsect]
