/* boost random/cauchy_distribution.hpp header file

 *

 * Copyright Jens Maurer 2000-2001

 * Distributed under the Boost Software License, Version 1.0. (See

 * accompanying file LICENSE_1_0.txt or copy at

 * http://www.boost.org/LICENSE_1_0.txt)

 *

 * See http://www.boost.org for most recent version including documentation.

 *

 * $Id: cauchy_distribution.hpp,v 1.15 2004/07/27 03:43:32 dgregor 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 <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;

#endif

// Cauchy distribution: p(x) = sigma/(pi*(sigma**2 + (x-median)**2))

template<class RealType = double>

class cauchy_distribution

{

public:

  typedef RealType input_type;

  typedef RealType result_type;

#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS

  BOOST_STATIC_ASSERT(!std::numeric_limits<RealType>::is_integer);

#endif

  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);

#ifndef BOOST_NO_STDC_NAMESPACE

    using std::tan;

#endif

    return _median + _sigma * tan(pi*(eng()-result_type(0.5)));

  }

#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)

  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;

  }

#endif

private:

  result_type _median, _sigma;

};

} // namespace boost

#endif // BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP