boost/random/random_number_generator.hpp

0001 /* boost random/random_number_generator.hpp header file
0002  *
0003  * Copyright Jens Maurer 2000-2001
0004  * Distributed under the Boost Software License, Version 1.0. (See
0005  * accompanying file LICENSE_1_0.txt or copy at
0006  * http://www.boost.org/LICENSE_1_0.txt)
0007  *
0008  * See http://www.boost.org for most recent version including documentation.
0009  *
0010  * $Id$
0011  *
0012  * Revision history
0013  *  2001-02-18  moved to individual header files
0014  */
0015
0016 #ifndef BOOST_RANDOM_RANDOM_NUMBER_GENERATOR_HPP
0017 #define BOOST_RANDOM_RANDOM_NUMBER_GENERATOR_HPP
0018
0019 #include <boost/assert.hpp>
0020 #include <boost/random/uniform_int_distribution.hpp>
0021
0022 #include <boost/random/detail/disable_warnings.hpp>
0023
0024 namespace boost {
0025 namespace random {
0026
0027 /**
0028  * Instantiations of class template random_number_generator model a
0029  * RandomNumberGenerator (std:25.2.11 [lib.alg.random.shuffle]). On
0030  * each invocation, it returns a uniformly distributed integer in
0031  * the range [0..n).
0032  *
0033  * The template parameter IntType shall denote some integer-like value type.
0034  */
0035 template<class URNG, class IntType = long>
0036 class random_number_generator
0037 {
0038 public:
0039     typedef URNG base_type;
0040     typedef IntType argument_type;
0041     typedef IntType result_type;
0042     /**
0043      * Constructs a random_number_generator functor with the given
0044      * \uniform_random_number_generator as the underlying source of
0045      * random numbers.
0046      */
0047     random_number_generator(base_type& rng) : _rng(rng) {}
0048
0049     // compiler-generated copy ctor is fine
0050     // assignment is disallowed because there is a reference member
0051
0052     /**
0053      * Returns a value in the range [0, n)
0054      */
0055     result_type operator()(argument_type n)
0056     {
0057         BOOST_ASSERT(n > 0);
0058         return uniform_int_distribution<IntType>(0, n-1)(_rng);
0059     }
0060
0061 private:
0062     base_type& _rng;
0063 };
0064
0065 } // namespace random
0066
0067 using random::random_number_generator;
0068
0069 } // namespace boost
0070
0071 #include <boost/random/detail/enable_warnings.hpp>
0072
0073 #endif // BOOST_RANDOM_RANDOM_NUMBER_GENERATOR_HPP