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boost/random/bernoulli_distribution.hpp
/* boost random/bernoulli_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: bernoulli_distribution.hpp 41369 2007-11-25 18:07:19Z bemandawes $
*
* Revision history
* 2001-02-18 moved to individual header files
*/

#ifndef BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
#define BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP

#include <cassert>
#include <iostream>

namespace boost {

// Bernoulli distribution: p(true) = p, p(false) = 1-p (boolean)
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;

explicit bernoulli_distribution(const RealType& p_arg = RealType(0.5))
: _p(p_arg)
{
assert(_p >= 0);
assert(_p <= 1);
}

// compiler-generated copy ctor and assignment operator are fine

RealType p() const { return _p; }
void reset() { }

template<class Engine>
result_type operator()(Engine& eng)
{
if(_p == RealType(0))
return false;
else
return RealType(eng() - (eng.min)()) <= _p * RealType((eng.max)()-(eng.min)());
}

#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 bernoulli_distribution& bd)
{
os << bd._p;
return os;
}

template<class CharT, class Traits>
friend std::basic_istream<CharT,Traits>&
operator>>(std::basic_istream<CharT,Traits>& is, bernoulli_distribution& bd)
{
is >> std::ws >> bd._p;
return is;
}
#endif

private:
RealType _p;
};

} // namespace boost

#endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP

参考资料：http://www.boost.org/doc/libs/1_35_0/boost/random/bernoulli_distribution.hpp