Chris@16: /* boost random/geometric_distribution.hpp header file
Chris@16:  *
Chris@16:  * Copyright Jens Maurer 2000-2001
Chris@16:  * Copyright Steven Watanabe 2011
Chris@16:  * Distributed under the Boost Software License, Version 1.0. (See
Chris@16:  * accompanying file LICENSE_1_0.txt or copy at
Chris@16:  * http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  *
Chris@16:  * See http://www.boost.org for most recent version including documentation.
Chris@16:  *
Chris@101:  * $Id$
Chris@16:  *
Chris@16:  * Revision history
Chris@16:  *  2001-02-18  moved to individual header files
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP
Chris@16: #define BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP
Chris@16: 
Chris@16: #include <boost/config/no_tr1/cmath.hpp>          // std::log
Chris@16: #include <iosfwd>
Chris@16: #include <ios>
Chris@16: #include <boost/assert.hpp>
Chris@16: #include <boost/random/detail/config.hpp>
Chris@16: #include <boost/random/detail/operators.hpp>
Chris@16: #include <boost/random/uniform_01.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: 
Chris@16: /**
Chris@16:  * An instantiation of the class template @c geometric_distribution models
Chris@16:  * a \random_distribution.  The distribution produces positive
Chris@16:  * integers which are the number of bernoulli trials
Chris@16:  * with probability @c p required to get one that fails.
Chris@16:  *
Chris@16:  * For the geometric distribution, \f$p(i) = p(1-p)^{i}\f$.
Chris@16:  *
Chris@16:  * @xmlwarning
Chris@16:  * This distribution has been updated to match the C++ standard.
Chris@16:  * Its behavior has changed from the original
Chris@16:  * boost::geometric_distribution.  A backwards compatible
Chris@16:  * wrapper is provided in namespace boost.
Chris@16:  * @endxmlwarning
Chris@16:  */
Chris@16: template<class IntType = int, class RealType = double>
Chris@16: class geometric_distribution
Chris@16: {
Chris@16: public:
Chris@16:     typedef RealType input_type;
Chris@16:     typedef IntType result_type;
Chris@16: 
Chris@16:     class param_type
Chris@16:     {
Chris@16:     public:
Chris@16: 
Chris@16:         typedef geometric_distribution distribution_type;
Chris@16: 
Chris@16:         /** Constructs the parameters with p. */
Chris@16:         explicit param_type(RealType p_arg = RealType(0.5))
Chris@16:           : _p(p_arg)
Chris@16:         {
Chris@16:             BOOST_ASSERT(RealType(0) < _p && _p < RealType(1));
Chris@16:         }
Chris@16: 
Chris@16:         /** Returns the p parameter of the distribution. */
Chris@16:         RealType p() const { return _p; }
Chris@16: 
Chris@16:         /** Writes the parameters to a std::ostream. */
Chris@16:         BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
Chris@16:         {
Chris@16:             os << parm._p;
Chris@16:             return os;
Chris@16:         }
Chris@16: 
Chris@16:         /** Reads the parameters from a std::istream. */
Chris@16:         BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
Chris@16:         {
Chris@16:             double p_in;
Chris@16:             if(is >> p_in) {
Chris@16:                 if(p_in > RealType(0) && p_in < RealType(1)) {
Chris@16:                     parm._p = p_in;
Chris@16:                 } else {
Chris@16:                     is.setstate(std::ios_base::failbit);
Chris@16:                 }
Chris@16:             }
Chris@16:             return is;
Chris@16:         }
Chris@16: 
Chris@16:         /** Returns true if the two sets of parameters are equal. */
Chris@16:         BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
Chris@16:         { return lhs._p == rhs._p; }
Chris@16: 
Chris@16:         /** Returns true if the two sets of parameters are different. */
Chris@16:         BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
Chris@16: 
Chris@16: 
Chris@16:     private:
Chris@16:         RealType _p;
Chris@16:     };
Chris@16: 
Chris@16:     /**
Chris@16:      * Contructs a new geometric_distribution with the paramter @c p.
Chris@16:      *
Chris@16:      * Requires: 0 < p < 1
Chris@16:      */
Chris@101:     explicit geometric_distribution(const RealType& p_arg = RealType(0.5))
Chris@101:       : _p(p_arg)
Chris@16:     {
Chris@16:         BOOST_ASSERT(RealType(0) < _p && _p < RealType(1));
Chris@16:         init();
Chris@16:     }
Chris@16: 
Chris@16:     /** Constructs a new geometric_distribution from its parameters. */
Chris@16:     explicit geometric_distribution(const param_type& parm)
Chris@16:       : _p(parm.p())
Chris@16:     {
Chris@16:         init();
Chris@16:     }
Chris@16: 
Chris@16:     // compiler-generated copy ctor and assignment operator are fine
Chris@16: 
Chris@16:     /** Returns: the distribution parameter @c p  */
Chris@16:     RealType p() const { return _p; }
Chris@16: 
Chris@16:     /** Returns the smallest value that the distribution can produce. */
Chris@16:     IntType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return IntType(0); }
Chris@16: 
Chris@16:     /** Returns the largest value that the distribution can produce. */
Chris@16:     IntType max BOOST_PREVENT_MACRO_SUBSTITUTION () const
Chris@16:     { return (std::numeric_limits<IntType>::max)(); }
Chris@16: 
Chris@16:     /** Returns the parameters of the distribution. */
Chris@16:     param_type param() const { return param_type(_p); }
Chris@16: 
Chris@16:     /** Sets the parameters of the distribution. */
Chris@16:     void param(const param_type& parm)
Chris@16:     {
Chris@16:         _p = parm.p();
Chris@16:         init();
Chris@16:     }
Chris@16:   
Chris@16:     /**
Chris@16:      * Effects: Subsequent uses of the distribution do not depend
Chris@16:      * on values produced by any engine prior to invoking reset.
Chris@16:      */
Chris@16:     void reset() { }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns a random variate distributed according to the
Chris@16:      * geometric_distribution.
Chris@16:      */
Chris@16:     template<class Engine>
Chris@16:     result_type operator()(Engine& eng) const
Chris@16:     {
Chris@16:         using std::log;
Chris@16:         using std::floor;
Chris@16:         RealType x = RealType(1) - boost::uniform_01<RealType>()(eng);
Chris@16:         return IntType(floor(log(x) / _log_1mp));
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns a random variate distributed according to the
Chris@16:      * geometric distribution with parameters specified by param.
Chris@16:      */
Chris@16:     template<class Engine>
Chris@16:     result_type operator()(Engine& eng, const param_type& parm) const
Chris@16:     { return geometric_distribution(parm)(eng); }
Chris@16: 
Chris@16:     /** Writes the distribution to a @c std::ostream. */
Chris@16:     BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, geometric_distribution, gd)
Chris@16:     {
Chris@16:         os << gd._p;
Chris@16:         return os;
Chris@16:     }
Chris@16: 
Chris@16:     /** Reads the distribution from a @c std::istream. */
Chris@16:     BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, geometric_distribution, gd)
Chris@16:     {
Chris@16:         param_type parm;
Chris@16:         if(is >> parm) {
Chris@16:             gd.param(parm);
Chris@16:         }
Chris@16:         return is;
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns true if the two distributions will produce identical
Chris@16:      * sequences of values given equal generators.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(geometric_distribution, lhs, rhs)
Chris@16:     { return lhs._p == rhs._p; }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns true if the two distributions may produce different
Chris@16:      * sequences of values given equal generators.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(geometric_distribution)
Chris@16: 
Chris@16: private:
Chris@16: 
Chris@16:     /// \cond show_private
Chris@16: 
Chris@16:     void init()
Chris@16:     {
Chris@16:         using std::log;
Chris@16:         _log_1mp = log(1 - _p);
Chris@16:     }
Chris@16: 
Chris@16:     RealType _p;
Chris@16:     RealType _log_1mp;
Chris@16: 
Chris@16:     /// \endcond
Chris@16: };
Chris@16: 
Chris@16: } // namespace random
Chris@16: 
Chris@16: /// \cond show_deprecated
Chris@16: 
Chris@16: /**
Chris@16:  * Provided for backwards compatibility.  This class is
Chris@16:  * deprecated.  It provides the old behavior of geometric_distribution
Chris@16:  * with \f$p(i) = (1-p) p^{i-1}\f$.
Chris@16:  */
Chris@16: template<class IntType = int, class RealType = double>
Chris@16: class geometric_distribution
Chris@16: {
Chris@16: public:
Chris@16:     typedef RealType input_type;
Chris@16:     typedef IntType result_type;
Chris@16: 
Chris@16:     explicit geometric_distribution(RealType p_arg = RealType(0.5))
Chris@16:       : _impl(1 - p_arg) {}
Chris@16: 
Chris@16:     RealType p() const { return 1 - _impl.p(); }
Chris@16: 
Chris@16:     void reset() {}
Chris@16: 
Chris@16:     template<class Engine>
Chris@16:     IntType operator()(Engine& eng) const { return _impl(eng) + IntType(1); }
Chris@16: 
Chris@16:     BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, geometric_distribution, gd)
Chris@16:     {
Chris@16:         os << gd.p();
Chris@16:         return os;
Chris@16:     }
Chris@16: 
Chris@16:     BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, geometric_distribution, gd)
Chris@16:     {
Chris@16:         RealType val;
Chris@16:         if(is >> val) {
Chris@16:             typename impl_type::param_type impl_param(1 - val);
Chris@16:             gd._impl.param(impl_param);
Chris@16:         }
Chris@16:         return is;
Chris@16:     }
Chris@16: 
Chris@16: private:
Chris@16:     typedef random::geometric_distribution<IntType, RealType> impl_type;
Chris@16:     impl_type _impl;
Chris@16: };
Chris@16: 
Chris@16: /// \endcond
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP