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 1.1.1.1 2006/03/20 20:15:10 ewalkup 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 24 namespace 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)) 33 template<class RealType = double> 34 class cauchy_distribution 35 { 36 public: 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 cauchy_distribution(result_type median=result_type (0),result_type sigma=result_type (1))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 median() const50 result_type median() const { return _median; } sigma() const51 result_type sigma() const { return _sigma; } reset()52 void reset() { } 53 54 template<class Engine> operator ()(Engine & eng)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>& operator <<(std::basic_ostream<CharT,Traits> & os,const cauchy_distribution & cd)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>& operator >>(std::basic_istream<CharT,Traits> & is,cauchy_distribution & cd)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 83 private: 84 result_type _median, _sigma; 85 }; 86 87 } // namespace boost 88 89 #endif // BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP 90