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/* boost random/bernoulli_distribution.hpp header file
*
* Copyright Jens Maurer 2000-2001
* Copyright Steven Watanabe 2011
* 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.
*
* $Id$
*
* Revision history
* 2001-02-18 moved to individual header files
*/
#ifndef BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
#define BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
#include <iosfwd>
#include <boost/assert.hpp>
#include <boost/random/detail/config.hpp>
#include <boost/random/detail/operators.hpp>
namespace boost {
namespace random {
/**
* Instantiations of class template \bernoulli_distribution model a
* \random_distribution. Such a random distribution produces bool values
* distributed with probabilities P(true) = p and P(false) = 1-p. p is
* the parameter of the distribution.
*/
template<class RealType = double>
class bernoulli_distribution
{
public:
// In principle, this could work with both integer and floating-point
// types. Generating floating-point random numbers in the first
// place is probably more expensive, so use integer as input.
typedef int input_type;
typedef bool result_type;
class param_type
{
public:
typedef bernoulli_distribution distribution_type;
/**
* Constructs the parameters of the distribution.
*
* Requires: 0 <= p <= 1
*/
explicit param_type(RealType p_arg = RealType(0.5))
: _p(p_arg)
{
BOOST_ASSERT(_p >= 0);
BOOST_ASSERT(_p <= 1);
}
/** Returns the p parameter of the distribution. */
RealType p() const { return _p; }
/** Writes the parameters to a std::ostream. */
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
{
os << parm._p;
return os;
}
/** Reads the parameters from a std::istream. */
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
{
is >> parm._p;
return is;
}
/** Returns true if the two sets of parameters are equal. */
BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
{ return lhs._p == rhs._p; }
/** Returns true if the two sets of parameters are different. */
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
private:
RealType _p;
};
/**
* Constructs a \bernoulli_distribution object.
* p is the parameter of the distribution.
*
* Requires: 0 <= p <= 1
*/
explicit bernoulli_distribution(const RealType& p_arg = RealType(0.5))
: _p(p_arg)
{
BOOST_ASSERT(_p >= 0);
BOOST_ASSERT(_p <= 1);
}
/**
* Constructs \bernoulli_distribution from its parameters
*/
explicit bernoulli_distribution(const param_type& parm)
: _p(parm.p()) {}
// compiler-generated copy ctor and assignment operator are fine
/**
* Returns: The "p" parameter of the distribution.
*/
RealType p() const { return _p; }
/** Returns the smallest value that the distribution can produce. */
bool min BOOST_PREVENT_MACRO_SUBSTITUTION () const
{ return false; }
/** Returns the largest value that the distribution can produce. */
bool max BOOST_PREVENT_MACRO_SUBSTITUTION () const
{ return true; }
/** Returns the parameters of the distribution. */
param_type param() const { return param_type(_p); }
/** Sets the parameters of the distribution. */
void param(const param_type& parm) { _p = parm.p(); }
/**
* Effects: Subsequent uses of the distribution do not depend
* on values produced by any engine prior to invoking reset.
*/
void reset() { }
/**
* Returns: a random variate distributed according to the
* \bernoulli_distribution.
*/
template<class Engine>
bool operator()(Engine& eng) const
{
if(_p == RealType(0))
return false;
else
return RealType(eng() - (eng.min)()) <= _p * RealType((eng.max)()-(eng.min)());
}
/**
* Returns: a random variate distributed according to the
* \bernoulli_distribution with parameters specified by param.
*/
template<class Engine>
bool operator()(Engine& eng, const param_type& parm) const
{
return bernoulli_distribution(parm)(eng);
}
/**
* Writes the parameters of the distribution to a @c std::ostream.
*/
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, bernoulli_distribution, bd)
{
os << bd._p;
return os;
}
/**
* Reads the parameters of the distribution from a @c std::istream.
*/
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, bernoulli_distribution, bd)
{
is >> bd._p;
return is;
}
/**
* Returns true iff the two distributions will produce identical
* sequences of values given equal generators.
*/
BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(bernoulli_distribution, lhs, rhs)
{ return lhs._p == rhs._p; }
/**
* Returns true iff the two distributions will produce different
* sequences of values given equal generators.
*/
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(bernoulli_distribution)
private:
RealType _p;
};
} // namespace random
using random::bernoulli_distribution;
} // namespace boost
#endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
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