A random variate generator is used to join a random number generator together with a random number distribution. Boost.Random provides a vast choice of generators as well as distributions .
variate_generator
#include <boost/random/variate_generator.hpp>
template<class Engine, class Distribution>
class variate_generator
{
public:
typedef Engine engine_type;
typedef Distribution distribution_type;
typedef typename Distribution::result_type result_type;
variate_generator(Engine e, Distribution d);
result_type operator()();
template<class T>
result_type operator()(T value);
engine_value_type& engine();
const engine_value_type& engine() const;
result_type min() const;
result_type max() const;
};
Instantations of class template variate_generator model a
number generator.
The argument for the template parameter Engine shall be of
the form U, U&, or U*, where U models a uniform random number
generator. Then, the member engine_value_type names U (not the
pointer or reference to U).
Specializations of variate_generator satisfy the
requirements of CopyConstructible. They also satisfy the requirements of
Assignable unless the template parameter Engine is of the form U&.
The complexity of all functions specified in this section is constant. No function described in this section except the constructor throws an exception.
variate_generator(engine_type eng, distribution_type d)
Effects: Constructs a variate_generator
object with the associated uniform random number generator eng
and the associated random distribution d.
Throws: If and what the copy constructor of Engine or
Distribution throws.
result_type operator()()
Returns: distribution()(e)
Notes: The sequence of numbers produced by the uniform
random number generator e, se, is obtained from the
sequence of numbers produced by the associated uniform random number
generator eng, seng, as follows: Consider the
values of numeric_limits<T>::is_integer for
T both Distribution::input_type and
engine_value_type::result_type. If the values for both types
are true, then se is identical to seng.
Otherwise, if the values for both types are false, then the
numbers in seng are divided by
engine().max()-engine().min() to obtain the numbers in
se. Otherwise, if the value for
engine_value_type::result_type is true and the
value for Distribution::input_type is false, then
the numbers in seng are divided by
engine().max()-engine().min()+1 to obtain the numbers in
se. Otherwise, the mapping from seng to se
is implementation-defined. In all cases, an implicit conversion from
engine_value_type::result_type to
Distribution::input_type is performed. If such a conversion
does not exist, the program is ill-formed.
template<class T> result_type operator()(T value)
Returns: distribution()(e, value). For the
semantics of e, see the description of
operator()().
engine_value_type& engine()
Returns: A reference to the associated uniform random number generator.
const engine_value_type& engine() const
Returns: A reference to the associated uniform random number generator.
distribution_type& distribution()
Returns: A reference to the associated random distribution.
const distribution_type& distribution() const
Returns: A reference to the associated random distribution.
result_type min() const
Precondition: distribution().min() is
well-formed
Returns: distribution().min()
result_type max() const
Precondition: distribution().max() is
well-formed
Returns: distribution().max()
Revised 05 December, 2006
Copyright © 2003-2004 Jens Maurer
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)