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/* boost random/uniform_real_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.
*
* $Id$
*
*/
#ifndef BOOST_RANDOM_UNIFORM_REAL_DISTRIBUTION_HPP
#define BOOST_RANDOM_UNIFORM_REAL_DISTRIBUTION_HPP
#include <iosfwd>
#include <ios>
#include <istream>
#include <boost/assert.hpp>
#include <boost/config.hpp>
#include <boost/random/detail/config.hpp>
#include <boost/random/detail/operators.hpp>
#include <boost/random/detail/signed_unsigned_tools.hpp>
#include <boost/type_traits/is_integral.hpp>
#include <boost/mpl/bool.hpp>
namespace boost {
namespace random {
namespace detail {
template<class Engine, class T>
T generate_uniform_real(
Engine& eng, T min_value, T max_value,
boost::mpl::false_ /** is_integral<Engine::result_type> */)
{
for(;;) {
typedef T result_type;
result_type numerator = static_cast<T>(eng() - (eng.min)());
result_type divisor = static_cast<T>((eng.max)() - (eng.min)());
BOOST_ASSERT(divisor > 0);
BOOST_ASSERT(numerator >= 0 && numerator <= divisor);
T result = numerator / divisor * (max_value - min_value) + min_value;
if(result < max_value) return result;
}
}
template<class Engine, class T>
T generate_uniform_real(
Engine& eng, T min_value, T max_value,
boost::mpl::true_ /** is_integral<Engine::result_type> */)
{
for(;;) {
typedef T result_type;
typedef typename Engine::result_type base_result;
result_type numerator = static_cast<T>(subtract<base_result>()(eng(), (eng.min)()));
result_type divisor = static_cast<T>(subtract<base_result>()((eng.max)(), (eng.min)())) + 1;
BOOST_ASSERT(divisor > 0);
BOOST_ASSERT(numerator >= 0 && numerator <= divisor);
T result = numerator / divisor * (max_value - min_value) + min_value;
if(result < max_value) return result;
}
}
template<class Engine, class T>
inline T generate_uniform_real(Engine& eng, T min_value, T max_value)
{
if(max_value / 2 - min_value / 2 > (std::numeric_limits<T>::max)() / 2)
return 2 * generate_uniform_real(eng, min_value / 2, max_value / 2);
typedef typename Engine::result_type base_result;
return generate_uniform_real(eng, min_value, max_value,
boost::is_integral<base_result>());
}
}
/**
* The class template uniform_real_distribution models a \random_distribution.
* On each invocation, it returns a random floating-point value uniformly
* distributed in the range [min..max).
*/
template<class RealType = double>
class uniform_real_distribution
{
public:
typedef RealType input_type;
typedef RealType result_type;
class param_type
{
public:
typedef uniform_real_distribution distribution_type;
/**
* Constructs the parameters of a uniform_real_distribution.
*
* Requires min <= max
*/
explicit param_type(RealType min_arg = RealType(0.0),
RealType max_arg = RealType(1.0))
: _min(min_arg), _max(max_arg)
{
BOOST_ASSERT(_min < _max);
}
/** Returns the minimum value of the distribution. */
RealType a() const { return _min; }
/** Returns the maximum value of the distribution. */
RealType b() const { return _max; }
/** Writes the parameters to a @c std::ostream. */
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
{
os << parm._min << " " << parm._max;
return os;
}
/** Reads the parameters from a @c std::istream. */
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
{
RealType min_in, max_in;
if(is >> min_in >> std::ws >> max_in) {
if(min_in <= max_in) {
parm._min = min_in;
parm._max = max_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._min == rhs._min && lhs._max == rhs._max; }
/** Returns true if the two sets of parameters are different. */
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
private:
RealType _min;
RealType _max;
};
/**
* Constructs a uniform_real_distribution. @c min and @c max are
* the parameters of the distribution.
*
* Requires: min <= max
*/
explicit uniform_real_distribution(
RealType min_arg = RealType(0.0),
RealType max_arg = RealType(1.0))
: _min(min_arg), _max(max_arg)
{
BOOST_ASSERT(min_arg < max_arg);
}
/** Constructs a uniform_real_distribution from its parameters. */
explicit uniform_real_distribution(const param_type& parm)
: _min(parm.a()), _max(parm.b()) {}
/** Returns the minimum value of the distribution */
RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
/** Returns the maximum value of the distribution */
RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
/** Returns the minimum value of the distribution */
RealType a() const { return _min; }
/** Returns the maximum value of the distribution */
RealType b() const { return _max; }
/** Returns the parameters of the distribution. */
param_type param() const { return param_type(_min, _max); }
/** Sets the parameters of the distribution. */
void param(const param_type& parm)
{
_min = parm.a();
_max = parm.b();
}
/**
* Effects: Subsequent uses of the distribution do not depend
* on values produced by any engine prior to invoking reset.
*/
void reset() { }
/** Returns a value uniformly distributed in the range [min, max). */
template<class Engine>
result_type operator()(Engine& eng) const
{ return detail::generate_uniform_real(eng, _min, _max); }
/**
* Returns a value uniformly distributed in the range
* [param.a(), param.b()).
*/
template<class Engine>
result_type operator()(Engine& eng, const param_type& parm) const
{ return detail::generate_uniform_real(eng, parm.a(), parm.b()); }
/** Writes the distribution to a @c std::ostream. */
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, uniform_real_distribution, ud)
{
os << ud.param();
return os;
}
/** Reads the distribution from a @c std::istream. */
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, uniform_real_distribution, ud)
{
param_type parm;
if(is >> parm) {
ud.param(parm);
}
return is;
}
/**
* Returns true if the two distributions will produce identical sequences
* of values given equal generators.
*/
BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(uniform_real_distribution, lhs, rhs)
{ return lhs._min == rhs._min && lhs._max == rhs._max; }
/**
* Returns true if the two distributions may produce different sequences
* of values given equal generators.
*/
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(uniform_real_distribution)
private:
RealType _min;
RealType _max;
};
} // namespace random
} // namespace boost
#endif // BOOST_RANDOM_UNIFORM_INT_HPP
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