// Copyright 2004 The Trustees of Indiana University.

 // Distributed under 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)

 //  Authors: Douglas Gregor

 //           Andrew Lumsdaine

 #ifndef BOOST_GRAPH_CIRCLE_LAYOUT_HPP

 #define BOOST_GRAPH_CIRCLE_LAYOUT_HPP

 #include <cmath>

 #include <utility>

 #include <boost/graph/graph_traits.hpp>

 namespace boost {

   /** 

    * \brief Layout the graph with the vertices at the points of a regular

    * n-polygon. 

    *

    * The distance from the center of the polygon to each point is

    * determined by the @p radius parameter. The @p position parameter

    * must be an Lvalue Property Map whose value type is a class type

    * containing @c x and @c y members that will be set to the @c x and

    * @c y coordinates.

    */

   template<typename VertexListGraph, typename PositionMap, typename Radius>

   void 

   circle_graph_layout(const VertexListGraph& g, PositionMap position,

                       Radius radius)

   {

     const double pi = 3.14159;

 #ifndef BOOST_NO_STDC_NAMESPACE

     using std::sin;

     using std::cos;

 #endif // BOOST_NO_STDC_NAMESPACE

     typedef typename graph_traits<VertexListGraph>::vertices_size_type 

       vertices_size_type;

     vertices_size_type n = num_vertices(g);

     typedef typename graph_traits<VertexListGraph>::vertex_iterator 

       vertex_iterator;

     vertices_size_type i = 0;

     for(std::pair<vertex_iterator, vertex_iterator> v = vertices(g); 

         v.first != v.second; ++v.first, ++i) {

       position[*v.first].x = radius * cos(i * 2 * pi / n);

       position[*v.first].y = radius * sin(i * 2 * pi / n);

     }

   }

 } // end namespace boost

 #endif // BOOST_GRAPH_CIRCLE_LAYOUT_HPP