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

Revision 857, 2.6 KB checked in by igarcia, 19 years ago (diff)
Line 
1/* boost random/cauchy_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: cauchy_distribution.hpp,v 1.15 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_CAUCHY_DISTRIBUTION_HPP
17#define BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
18
19#include <cmath>
20#include <iostream>
21#include <boost/limits.hpp>
22#include <boost/static_assert.hpp>
23
24namespace boost {
25
26#if defined(__GNUC__) && (__GNUC__ < 3)
27// Special gcc workaround: gcc 2.95.x ignores using-declarations
28// in template classes (confirmed by gcc author Martin v. Loewis)
29  using std::tan;
30#endif
31
32// Cauchy distribution: p(x) = sigma/(pi*(sigma**2 + (x-median)**2))
33template<class RealType = double>
34class cauchy_distribution
35{
36public:
37  typedef RealType input_type;
38  typedef RealType result_type;
39
40#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
41  BOOST_STATIC_ASSERT(!std::numeric_limits<RealType>::is_integer);
42#endif
43
44  explicit cauchy_distribution(result_type median = result_type(0),
45                               result_type sigma = result_type(1))
46    : _median(median), _sigma(sigma) { }
47
48  // compiler-generated copy ctor and assignment operator are fine
49
50  result_type median() const { return _median; }
51  result_type sigma() const { return _sigma; }
52  void reset() { }
53
54  template<class Engine>
55  result_type operator()(Engine& eng)
56  {
57    // Can we have a boost::mathconst please?
58    const result_type pi = result_type(3.14159265358979323846);
59#ifndef BOOST_NO_STDC_NAMESPACE
60    using std::tan;
61#endif
62    return _median + _sigma * tan(pi*(eng()-result_type(0.5)));
63  }
64
65#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
66  template<class CharT, class Traits>
67  friend std::basic_ostream<CharT,Traits>&
68  operator<<(std::basic_ostream<CharT,Traits>& os, const cauchy_distribution& cd)
69  {
70    os << cd._median << " " << cd._sigma;
71    return os;
72  }
73
74  template<class CharT, class Traits>
75  friend std::basic_istream<CharT,Traits>&
76  operator>>(std::basic_istream<CharT,Traits>& is, cauchy_distribution& cd)
77  {
78    is >> std::ws >> cd._median >> std::ws >> cd._sigma;
79    return is;
80  }
81#endif
82
83private:
84  result_type _median, _sigma;
85};
86
87} // namespace boost
88
89#endif // BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
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