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1 /* boost random/cauchy_distribution.hpp header file |
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2 * |
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3 * Copyright Jens Maurer 2000-2001 |
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4 * Distributed under the Boost Software License, Version 1.0. (See |
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5 * accompanying file LICENSE_1_0.txt or copy at |
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6 * http://www.boost.org/LICENSE_1_0.txt) |
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7 * |
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8 * See http://www.boost.org for most recent version including documentation. |
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9 * |
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10 * $Id: cauchy_distribution.hpp,v 1.15 2004/07/27 03:43:32 dgregor Exp $ |
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11 * |
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12 * Revision history |
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13 * 2001-02-18 moved to individual header files |
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14 */ |
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15 |
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16 #ifndef BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP |
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17 #define BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP |
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18 |
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19 #include <cmath> |
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20 #include <iostream> |
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21 #include <boost/limits.hpp> |
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22 #include <boost/static_assert.hpp> |
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23 |
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24 namespace boost { |
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25 |
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26 #if defined(__GNUC__) && (__GNUC__ < 3) |
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27 // Special gcc workaround: gcc 2.95.x ignores using-declarations |
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28 // in template classes (confirmed by gcc author Martin v. Loewis) |
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29 using std::tan; |
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30 #endif |
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31 |
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32 // Cauchy distribution: p(x) = sigma/(pi*(sigma**2 + (x-median)**2)) |
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33 template<class RealType = double> |
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34 class cauchy_distribution |
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35 { |
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36 public: |
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37 typedef RealType input_type; |
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38 typedef RealType result_type; |
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39 |
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40 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS |
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41 BOOST_STATIC_ASSERT(!std::numeric_limits<RealType>::is_integer); |
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42 #endif |
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43 |
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44 explicit cauchy_distribution(result_type median = result_type(0), |
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45 result_type sigma = result_type(1)) |
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46 : _median(median), _sigma(sigma) { } |
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47 |
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48 // compiler-generated copy ctor and assignment operator are fine |
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49 |
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50 result_type median() const { return _median; } |
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51 result_type sigma() const { return _sigma; } |
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52 void reset() { } |
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53 |
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54 template<class Engine> |
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55 result_type operator()(Engine& eng) |
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56 { |
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57 // Can we have a boost::mathconst please? |
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58 const result_type pi = result_type(3.14159265358979323846); |
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59 #ifndef BOOST_NO_STDC_NAMESPACE |
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60 using std::tan; |
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61 #endif |
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62 return _median + _sigma * tan(pi*(eng()-result_type(0.5))); |
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63 } |
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64 |
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65 #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) |
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66 template<class CharT, class Traits> |
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67 friend std::basic_ostream<CharT,Traits>& |
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68 operator<<(std::basic_ostream<CharT,Traits>& os, const cauchy_distribution& cd) |
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69 { |
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70 os << cd._median << " " << cd._sigma; |
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71 return os; |
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72 } |
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73 |
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74 template<class CharT, class Traits> |
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75 friend std::basic_istream<CharT,Traits>& |
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76 operator>>(std::basic_istream<CharT,Traits>& is, cauchy_distribution& cd) |
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77 { |
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78 is >> std::ws >> cd._median >> std::ws >> cd._sigma; |
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79 return is; |
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80 } |
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81 #endif |
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82 |
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83 private: |
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84 result_type _median, _sigma; |
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85 }; |
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86 |
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87 } // namespace boost |
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88 |
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89 #endif // BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP |