// 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