/* boost random/uniform_on_sphere.hpp header file

  *

  * Copyright Jens Maurer 2000-2001

  * 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)

  *

  * See http://www.boost.org for most recent version including documentation.

  *

  * $Id: uniform_on_sphere.hpp,v 1.11 2004/07/27 03:43:32 dgregor Exp $

  *

  * Revision history

  *  2001-02-18  moved to individual header files

  */

 #ifndef BOOST_RANDOM_UNIFORM_ON_SPHERE_HPP

 #define BOOST_RANDOM_UNIFORM_ON_SPHERE_HPP

 #include <vector>

 #include <algorithm>     // std::transform

 #include <functional>    // std::bind2nd, std::divides

 #include <boost/random/normal_distribution.hpp>

 namespace boost {

 template<class RealType = double, class Cont = std::vector<RealType> >

 class uniform_on_sphere

 {

 public:

   typedef RealType input_type;

   typedef Cont result_type;

   explicit uniform_on_sphere(int dim = 2) : _container(dim), _dim(dim) { }

   // compiler-generated copy ctor and assignment operator are fine

   void reset() { _normal.reset(); }

   template<class Engine>

   const result_type & operator()(Engine& eng)

   {

     RealType sqsum = 0;

     for(typename Cont::iterator it = _container.begin();

         it != _container.end();

         ++it) {

       RealType val = _normal(eng);

       *it = val;

       sqsum += val * val;

     }

 #ifndef BOOST_NO_STDC_NAMESPACE

     using std::sqrt;

 #endif

     // for all i: result[i] /= sqrt(sqsum)

     std::transform(_container.begin(), _container.end(), _container.begin(),

                    std::bind2nd(std::divides<RealType>(), sqrt(sqsum)));

     return _container;

   }

 #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)

   template<class CharT, class Traits>

   friend std::basic_ostream<CharT,Traits>&

   operator<<(std::basic_ostream<CharT,Traits>& os, const uniform_on_sphere& sd)

   {

     os << sd._dim;

     return os;

   }

   template<class CharT, class Traits>

   friend std::basic_istream<CharT,Traits>&

   operator>>(std::basic_istream<CharT,Traits>& is, uniform_on_sphere& sd)

   {

     is >> std::ws >> sd._dim;

     sd._container.resize(sd._dim);

     return is;

   }

 #endif

 private:

   normal_distribution<RealType> _normal;

   result_type _container;

   int _dim;

 };

 } // namespace boost

 #endif // BOOST_RANDOM_UNIFORM_ON_SPHERE_HPP