Chris@16: /* boost random/bernoulli_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_BERNOULLI_DISTRIBUTION_HPP
Chris@16: #define BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
Chris@16: 
Chris@16: #include <iosfwd>
Chris@16: #include <boost/assert.hpp>
Chris@16: #include <boost/random/detail/config.hpp>
Chris@16: #include <boost/random/detail/operators.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: 
Chris@16: /**
Chris@16:  * Instantiations of class template \bernoulli_distribution model a
Chris@16:  * \random_distribution. Such a random distribution produces bool values
Chris@16:  * distributed with probabilities P(true) = p and P(false) = 1-p. p is
Chris@16:  * the parameter of the distribution.
Chris@16:  */
Chris@16: template<class RealType = double>
Chris@16: class bernoulli_distribution
Chris@16: {
Chris@16: public:
Chris@16:     // In principle, this could work with both integer and floating-point
Chris@16:     // types.  Generating floating-point random numbers in the first
Chris@16:     // place is probably more expensive, so use integer as input.
Chris@16:     typedef int input_type;
Chris@16:     typedef bool result_type;
Chris@16: 
Chris@16:     class param_type
Chris@16:     {
Chris@16:     public:
Chris@16: 
Chris@16:         typedef bernoulli_distribution distribution_type;
Chris@16: 
Chris@16:         /** 
Chris@16:          * Constructs the parameters of the distribution.
Chris@16:          *
Chris@16:          * Requires: 0 <= p <= 1
Chris@16:          */
Chris@16:         explicit param_type(RealType p_arg = RealType(0.5))
Chris@16:           : _p(p_arg)
Chris@16:         {
Chris@16:             BOOST_ASSERT(_p >= 0);
Chris@16:             BOOST_ASSERT(_p <= 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:             is >> parm._p;
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:     private:
Chris@16:         RealType _p;
Chris@16:     };
Chris@16: 
Chris@16:     /** 
Chris@16:      * Constructs a \bernoulli_distribution object.
Chris@16:      * p is the parameter of the distribution.
Chris@16:      *
Chris@16:      * Requires: 0 <= p <= 1
Chris@16:      */
Chris@16:     explicit bernoulli_distribution(const RealType& p_arg = RealType(0.5)) 
Chris@16:       : _p(p_arg)
Chris@16:     {
Chris@16:         BOOST_ASSERT(_p >= 0);
Chris@16:         BOOST_ASSERT(_p <= 1);
Chris@16:     }
Chris@16:     /**
Chris@16:      * Constructs \bernoulli_distribution from its parameters
Chris@16:      */
Chris@16:     explicit bernoulli_distribution(const param_type& parm)
Chris@16:       : _p(parm.p()) {}
Chris@16: 
Chris@16:     // compiler-generated copy ctor and assignment operator are fine
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns: The "p" parameter of the distribution.
Chris@16:      */
Chris@16:     RealType p() const { return _p; }
Chris@16: 
Chris@16:     /** Returns the smallest value that the distribution can produce. */
Chris@16:     bool min BOOST_PREVENT_MACRO_SUBSTITUTION () const
Chris@16:     { return false; }
Chris@16:     /** Returns the largest value that the distribution can produce. */
Chris@16:     bool max BOOST_PREVENT_MACRO_SUBSTITUTION () const
Chris@16:     { return true; }
Chris@16: 
Chris@16:     /** Returns the parameters of the distribution. */
Chris@16:     param_type param() const { return param_type(_p); }
Chris@16:     /** Sets the parameters of the distribution. */
Chris@16:     void param(const param_type& parm) { _p = parm.p(); }
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:      * \bernoulli_distribution.
Chris@16:      */
Chris@16:     template<class Engine>
Chris@16:     bool operator()(Engine& eng) const
Chris@16:     {
Chris@16:         if(_p == RealType(0))
Chris@16:             return false;
Chris@16:         else
Chris@16:             return RealType(eng() - (eng.min)()) <= _p * RealType((eng.max)()-(eng.min)());
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns: a random variate distributed according to the
Chris@16:      * \bernoulli_distribution with parameters specified by param.
Chris@16:      */
Chris@16:     template<class Engine>
Chris@16:     bool operator()(Engine& eng, const param_type& parm) const
Chris@16:     {
Chris@16:         return bernoulli_distribution(parm)(eng);
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Writes the parameters of the distribution to a @c std::ostream.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, bernoulli_distribution, bd)
Chris@16:     {
Chris@16:         os << bd._p;
Chris@16:         return os;
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Reads the parameters of the distribution from a @c std::istream.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, bernoulli_distribution, bd)
Chris@16:     {
Chris@16:         is >> bd._p;
Chris@16:         return is;
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns true iff the two distributions will produce identical
Chris@16:      * sequences of values given equal generators.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(bernoulli_distribution, lhs, rhs)
Chris@16:     { return lhs._p == rhs._p; }
Chris@16:     
Chris@16:     /**
Chris@16:      * Returns true iff the two distributions will produce different
Chris@16:      * sequences of values given equal generators.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(bernoulli_distribution)
Chris@16: 
Chris@16: private:
Chris@16:     RealType _p;
Chris@16: };
Chris@16: 
Chris@16: } // namespace random
Chris@16: 
Chris@16: using random::bernoulli_distribution;
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP