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+/* 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 <boost/config/no_tr1/cmath.hpp> // std::log
+#include <iosfwd>
+#include <ios>
+#include <boost/assert.hpp>
+#include <boost/random/detail/config.hpp>
+#include <boost/random/detail/operators.hpp>
+#include <boost/random/uniform_01.hpp>
+
+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 IntType = int, class RealType = double>
+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<IntType>::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<class Engine>
+ result_type operator()(Engine& eng) const
+ {
+ using std::log;
+ using std::floor;
+ RealType x = RealType(1) - boost::uniform_01<RealType>()(eng);
+ return IntType(floor(log(x) / _log_1mp));
+ }
+
+ /**
+ * Returns a random variate distributed according to the
+ * geometric distribution with parameters specified by param.
+ */
+ template<class Engine>
+ 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 IntType = int, class RealType = double>
+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<class Engine>
+ 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<IntType, RealType> impl_type;
+ impl_type _impl;
+};
+
+/// \endcond
+
+} // namespace boost
+
+#endif // BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP