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/* boost random/cauchy_distribution.hpp header file
 * Copyright Jens Maurer 2000-2001
 * Permission to use, copy, modify, sell, and distribute this software
 * is hereby granted without fee provided that the above copyright notice
 * appears in all copies and that both that copyright notice and this
 * permission notice appear in supporting documentation,
 * Jens Maurer makes no representations about the suitability of this
 * software for any purpose. It is provided "as is" without express or
 * implied warranty.
 * See for most recent version including documentation.
 * $Id: cauchy_distribution.hpp,v 2004/01/25 21:26:45 jmaurer Exp $
 * Revision history
 *  2001-02-18  moved to individual header files


#include <cmath>
#include <iostream>
#include <boost/limits.hpp>
#include <boost/static_assert.hpp>

namespace boost {

#if defined(__GNUC__) && (__GNUC__ < 3)
// Special gcc workaround: gcc 2.95.x ignores using-declarations
// in template classes (confirmed by gcc author Martin v. Loewis)
  using std::tan;

// Cauchy distribution: p(x) = sigma/(pi*(sigma**2 + (x-median)**2))
template<class RealType = double>
class cauchy_distribution
  typedef RealType input_type;
  typedef RealType result_type;


  explicit cauchy_distribution(result_type median = result_type(0), 
                               result_type sigma = result_type(1))
    : _median(median), _sigma(sigma) { }

  // compiler-generated copy ctor and assignment operator are fine

  result_type median() const { return _median; }
  result_type sigma() const { return _sigma; }
  void reset() { }

  template<class Engine>
  result_type operator()(Engine& eng)
    // Can we have a boost::mathconst please?
    const result_type pi = result_type(3.14159265358979323846);
    using std::tan;
    return _median + _sigma * tan(pi*(eng()-result_type(0.5)));

  template<class CharT, class Traits>
  friend std::basic_ostream<CharT,Traits>&
  operator<<(std::basic_ostream<CharT,Traits>& os, const cauchy_distribution& cd)
    os << cd._median << " " << cd._sigma;
    return os;

  template<class CharT, class Traits>
  friend std::basic_istream<CharT,Traits>&
  operator>>(std::basic_istream<CharT,Traits>& is, cauchy_distribution& cd)
    is >> std::ws >> cd._median >> std::ws >> cd._sigma;
    return is;

  result_type _median, _sigma;

} // namespace boost