/* 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 http://www.boost.org for most recent version including documentation.
 *
 * $Id: cauchy_distribution.hpp,v 1.4 2001/11/14 21:53:38 jmaurer Exp $
 *
 * Revision history
 *  2001-02-18  moved to individual header files
 */

#ifndef BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
#define BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP

#include <cmath>
#include <boost/random/uniform_01.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;
#endif

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

  cauchy_distribution(base_type & rng, result_type median = 0, 
                      result_type sigma = 1)
    : _rng(rng), _median(median), _sigma(sigma) { }
  // compiler-generated copy constructor is fine
  // uniform_01 cannot be assigned, neither can this class
  result_type operator()()
  {
    const double pi = 3.14159265358979323846;
#ifndef BOOST_NO_STDC_NAMESPACE
    using std::tan;
#endif
    return _median + _sigma * tan(pi*(_rng()-0.5));
  }
#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
  friend bool operator==(const cauchy_distribution& x, 
                         const cauchy_distribution& y)
  {
    return x._median == y._median && x._sigma == y._sigma && x._rng == y._rng; 
  }
#else
  // Use a member function
  bool operator==(const cauchy_distribution& rhs) const
  {
    return _median == rhs._median && _sigma == rhs._sigma && _rng == rhs._rng;
  }
#endif
private:
  uniform_01<base_type, result_type> _rng;
  result_type _median, _sigma;
};

} // namespace boost

#endif // BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
