Boost Random Number Library Variate Generator

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 .

Class template variate_generator

Synopsis

#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;
};

Description

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, s_e, is obtained from the sequence of numbers produced by the associated uniform random number generator eng, s_eng, 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 s_e is identical to s_eng. Otherwise, if the values for both types are false, then the numbers in s_eng are divided by engine().max()-engine().min() to obtain the numbers in s_e. 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 s_eng are divided by engine().max()-engine().min()+1 to obtain the numbers in s_e. Otherwise, the mapping from s_eng to s_e 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)