/usr/include/boost/random
Edit: /usr/include/boost/random/geometric_distribution.hpp (7339B)
/* boost random/geometric_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_GEOMETRIC_DISTRIBUTION_HPP
#define BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP
#include
// std::log
#include
#include
#include
#include
#include
#include
namespace boost {
namespace random {
/**
* An instantiation of the class template @c geometric_distribution models
* a \random_distribution. The distribution produces positive
* integers which are the number of bernoulli trials
* with probability @c p required to get one that fails.
*
* For the geometric distribution, \f$p(i) = p(1-p)^{i}\f$.
*
* @xmlwarning
* This distribution has been updated to match the C++ standard.
* Its behavior has changed from the original
* boost::geometric_distribution. A backwards compatible
* wrapper is provided in namespace boost.
* @endxmlwarning
*/
template
class geometric_distribution
{
public:
typedef RealType input_type;
typedef IntType result_type;
class param_type
{
public:
typedef geometric_distribution distribution_type;
/** Constructs the parameters with p. */
explicit param_type(RealType p_arg = RealType(0.5))
: _p(p_arg)
{
BOOST_ASSERT(RealType(0) < _p && _p < RealType(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)
{
double p_in;
if(is >> p_in) {
if(p_in > RealType(0) && p_in < RealType(1)) {
parm._p = p_in;
} else {
is.setstate(std::ios_base::failbit);
}
}
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;
};
/**
* Contructs a new geometric_distribution with the paramter @c p.
*
* Requires: 0 < p < 1
*/
explicit geometric_distribution(const RealType& p_arg = RealType(0.5))
: _p(p_arg)
{
BOOST_ASSERT(RealType(0) < _p && _p < RealType(1));
init();
}
/** Constructs a new geometric_distribution from its parameters. */
explicit geometric_distribution(const param_type& parm)
: _p(parm.p())
{
init();
}
// compiler-generated copy ctor and assignment operator are fine
/** Returns: the distribution parameter @c p */
RealType p() const { return _p; }
/** Returns the smallest value that the distribution can produce. */
IntType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return IntType(0); }
/** Returns the largest value that the distribution can produce. */
IntType max BOOST_PREVENT_MACRO_SUBSTITUTION () const
{ return (std::numeric_limits::max)(); }
/** 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();
init();
}
/**
* 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
* geometric_distribution.
*/
template
result_type operator()(Engine& eng) const
{
using std::log;
using std::floor;
RealType x = RealType(1) - boost::uniform_01()(eng);
return IntType(floor(log(x) / _log_1mp));
}
/**
* Returns a random variate distributed according to the
* geometric distribution with parameters specified by param.
*/
template
result_type operator()(Engine& eng, const param_type& parm) const
{ return geometric_distribution(parm)(eng); }
/** Writes the distribution to a @c std::ostream. */
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, geometric_distribution, gd)
{
os << gd._p;
return os;
}
/** Reads the distribution from a @c std::istream. */
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, geometric_distribution, gd)
{
param_type parm;
if(is >> parm) {
gd.param(parm);
}
return is;
}
/**
* Returns true if the two distributions will produce identical
* sequences of values given equal generators.
*/
BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(geometric_distribution, lhs, rhs)
{ return lhs._p == rhs._p; }
/**
* Returns true if the two distributions may produce different
* sequences of values given equal generators.
*/
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(geometric_distribution)
private:
/// \cond show_private
void init()
{
using std::log;
_log_1mp = log(1 - _p);
}
RealType _p;
RealType _log_1mp;
/// \endcond
};
} // namespace random
/// \cond show_deprecated
/**
* Provided for backwards compatibility. This class is
* deprecated. It provides the old behavior of geometric_distribution
* with \f$p(i) = (1-p) p^{i-1}\f$.
*/
template
class geometric_distribution
{
public:
typedef RealType input_type;
typedef IntType result_type;
explicit geometric_distribution(RealType p_arg = RealType(0.5))
: _impl(1 - p_arg) {}
RealType p() const { return 1 - _impl.p(); }
void reset() {}
template
IntType operator()(Engine& eng) const { return _impl(eng) + IntType(1); }
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, geometric_distribution, gd)
{
os << gd.p();
return os;
}
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, geometric_distribution, gd)
{
RealType val;
if(is >> val) {
typename impl_type::param_type impl_param(1 - val);
gd._impl.param(impl_param);
}
return is;
}
private:
typedef random::geometric_distribution impl_type;
impl_type _impl;
};
/// \endcond
} // namespace boost
#endif // BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP