/* boost random/lognormal_distribution.hpp header file
 *
 * Copyright Jens Maurer 2000-2001
 * Permission to use, copy, modify, sell, and distribute this software
 * is hereby granted without free 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: lognormal_distribution.hpp,v 1.1 2001/04/14 13:28:42 jmaurer Exp $
 *
 * Revision history
 *  2001-02-18  moved to individual header files
 */

#ifndef BOOST_RANDOM_LOGNORMAL_DISTRIBUTION_HPP
#define BOOST_RANDOM_LOGNORMAL_DISTRIBUTION_HPP

#include <cmath>      // std::exp, std::sqrt
#include <cassert>
#include <boost/random/normal_distribution.hpp>

#ifdef BOOST_NO_STDC_NAMESPACE
namespace std {
  using ::log;
  using ::sqrt;
}
#endif

namespace boost {

#ifdef __GNUC__
// Special gcc workaround: gcc does not yet support using-declarations
// in template classes (confirmed by gcc author Martin v. Loewis)
  using std::sqrt;
  using std::exp;
#endif

template<class UniformRandomNumberGenerator, class RealType = double>
class lognormal_distribution
  : public generator_iterator_mixin_adapter<
      lognormal_distribution<UniformRandomNumberGenerator, RealType>, RealType>
{
public:
  typedef UniformRandomNumberGenerator base_type;
  typedef RealType result_type;
  lognormal_distribution(base_type & rng, result_type mean, 
                         result_type sigma)
    : _rng(rng, std::log(mean*mean/std::sqrt(sigma*sigma + mean*mean)),
           std::sqrt(std::log(sigma*sigma/mean/mean+1)))
  { 
    assert(mean > 0);
    this->iterator_init();
  }
  // compiler-generated copy constructor is fine
  // normal_distribution cannot be assigned, neither can this class
  result_type operator()()
  {
#ifndef BOOST_NO_STDC_NAMESPACE
    // allow for Koenig lookup
    using std::exp;
#endif
    return exp(_rng());
  }

#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
  friend bool operator==(const lognormal_distribution& x, 
                         const lognormal_distribution& y)
  { return x._rng == y._rng; }
#else
  // Use a member function
  bool operator==(const lognormal_distribution& rhs) const
  { return _rng == rhs._rng;  }
#endif
private:
  normal_distribution<base_type, result_type> _rng;
};

} // namespace boost

#endif // BOOST_RANDOM_LOGNORMAL_DISTRIBUTION_HPP
