1 /* boost random/uniform_on_sphere.hpp header file
3 * Copyright Jens Maurer 2000-2001
4 * Distributed under the Boost Software License, Version 1.0. (See
5 * accompanying file LICENSE_1_0.txt or copy at
6 * http://www.boost.org/LICENSE_1_0.txt)
8 * See http://www.boost.org for most recent version including documentation.
10 * $Id: uniform_on_sphere.hpp 60755 2010-03-22 00:45:06Z steven_watanabe $
13 * 2001-02-18 moved to individual header files
16 #ifndef BOOST_RANDOM_UNIFORM_ON_SPHERE_HPP
17 #define BOOST_RANDOM_UNIFORM_ON_SPHERE_HPP
20 #include <algorithm> // std::transform
21 #include <functional> // std::bind2nd, std::divides
22 #include <boost/random/detail/config.hpp>
23 #include <boost/random/normal_distribution.hpp>
28 * Instantiations of class template uniform_on_sphere model a
29 * \random_distribution. Such a distribution produces random
30 * numbers uniformly distributed on the unit sphere of arbitrary
31 * dimension @c dim. The @c Cont template parameter must be a STL-like
32 * container type with begin and end operations returning non-const
33 * ForwardIterators of type @c Cont::iterator. Each invocation of the
34 * @c UniformRandomNumberGenerator shall result in a floating-point
35 * value in the range [0,1).
37 template<class RealType = double, class Cont = std::vector<RealType> >
38 class uniform_on_sphere
41 typedef RealType input_type;
42 typedef Cont result_type;
45 * Constructs a @c uniform_on_sphere distribution.
46 * @c dim is the dimension of the sphere.
48 explicit uniform_on_sphere(int dim = 2) : _container(dim), _dim(dim) { }
50 // compiler-generated copy ctor and assignment operator are fine
52 void reset() { _normal.reset(); }
54 template<class Engine>
55 const result_type & operator()(Engine& eng)
58 for(typename Cont::iterator it = _container.begin();
59 it != _container.end();
61 RealType val = _normal(eng);
65 #ifndef BOOST_NO_STDC_NAMESPACE
68 // for all i: result[i] /= sqrt(sqsum)
69 std::transform(_container.begin(), _container.end(), _container.begin(),
70 std::bind2nd(std::divides<RealType>(), sqrt(sqsum)));
74 #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
75 template<class CharT, class Traits>
76 friend std::basic_ostream<CharT,Traits>&
77 operator<<(std::basic_ostream<CharT,Traits>& os, const uniform_on_sphere& sd)
83 template<class CharT, class Traits>
84 friend std::basic_istream<CharT,Traits>&
85 operator>>(std::basic_istream<CharT,Traits>& is, uniform_on_sphere& sd)
87 is >> std::ws >> sd._dim;
88 sd._container.resize(sd._dim);
94 normal_distribution<RealType> _normal;
95 result_type _container;
101 #endif // BOOST_RANDOM_UNIFORM_ON_SPHERE_HPP