source: NonGTP/Boost/boost/random/triangle_distribution.hpp @ 857

Revision 857, 2.6 KB checked in by igarcia, 19 years ago (diff)
Line 
1/* boost random/triangle_distribution.hpp header file
2 *
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)
7 *
8 * See http://www.boost.org for most recent version including documentation.
9 *
10 * $Id: triangle_distribution.hpp,v 1.11 2004/07/27 03:43:32 dgregor Exp $
11 *
12 * Revision history
13 *  2001-02-18  moved to individual header files
14 */
15
16#ifndef BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
17#define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
18
19#include <cmath>
20#include <cassert>
21#include <boost/random/uniform_01.hpp>
22
23namespace boost {
24
25// triangle distribution, with a smallest, b most probable, and c largest
26// value.
27template<class RealType = double>
28class triangle_distribution
29{
30public:
31  typedef RealType input_type;
32  typedef RealType result_type;
33
34  explicit triangle_distribution(result_type a = result_type(0),
35                                 result_type b = result_type(0.5),
36                                 result_type c = result_type(1))
37    : _a(a), _b(b), _c(c)
38  {
39    assert(_a <= _b && _b <= _c);
40    init();
41  }
42
43  // compiler-generated copy ctor and assignment operator are fine
44  result_type a() const { return _a; }
45  result_type b() const { return _b; }
46  result_type c() const { return _c; }
47
48  void reset() { }
49
50  template<class Engine>
51  result_type operator()(Engine& eng)
52  {
53#ifndef BOOST_NO_STDC_NAMESPACE
54    using std::sqrt;
55#endif
56    result_type u = eng();
57    if( u <= q1 )
58      return _a + p1*sqrt(u);
59    else
60      return _c - d3*sqrt(d2*u-d1);
61  }
62
63#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
64  template<class CharT, class Traits>
65  friend std::basic_ostream<CharT,Traits>&
66  operator<<(std::basic_ostream<CharT,Traits>& os, const triangle_distribution& td)
67  {
68    os << td._a << " " << td._b << " " << td._c;
69    return os;
70  }
71
72  template<class CharT, class Traits>
73  friend std::basic_istream<CharT,Traits>&
74  operator>>(std::basic_istream<CharT,Traits>& is, triangle_distribution& td)
75  {
76    is >> std::ws >> td._a >> std::ws >> td._b >> std::ws >> td._c;
77    td.init();
78    return is;
79  }
80#endif
81
82private:
83  void init()
84  {
85#ifndef BOOST_NO_STDC_NAMESPACE
86    using std::sqrt;
87#endif
88    d1 = _b - _a;
89    d2 = _c - _a;
90    d3 = sqrt(_c - _b);
91    q1 = d1 / d2;
92    p1 = sqrt(d1 * d2);
93  }
94
95  result_type _a, _b, _c;
96  result_type d1, d2, d3, q1, p1;
97};
98
99} // namespace boost
100
101#endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
Note: See TracBrowser for help on using the repository browser.