Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.


/* boost random/uniform_01.hpp header file
 * Copyright Jens Maurer 2000-2001
 * Permission to use, copy, modify, sell, and distribute this software
 * is hereby granted without fee provided that the above copyright notice
 * appears in all copies and that both that copyright notice and this
 * permission notice appear in supporting documentation,
 * Jens Maurer makes no representations about the suitability of this
 * software for any purpose. It is provided "as is" without express or
 * implied warranty.
 * See for most recent version including documentation.
 * $Id: uniform_01.hpp,v 2004/01/25 21:26:45 jmaurer Exp $
 * Revision history
 *  2001-02-18  moved to individual header files


#include <iostream>
#include <boost/config.hpp>
#include <boost/limits.hpp>
#include <boost/static_assert.hpp>

namespace boost {

// Because it is so commonly used: uniform distribution on the real [0..1)
// range.  This allows for specializations to avoid a costly int -> float
// conversion plus float multiplication
template<class UniformRandomNumberGenerator, class RealType = double>
class uniform_01
  typedef UniformRandomNumberGenerator base_type;
  typedef RealType result_type;

  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);


  explicit uniform_01(base_type rng)
    : _rng(rng),
      _factor(result_type(1) /
              (result_type(_rng.max()-_rng.min()) +
               result_type(std::numeric_limits<base_result>::is_integer ? 1 : 0)))
  // compiler-generated copy ctor and copy assignment are fine

  result_type min() const { return result_type(0); }
  result_type max() const { return result_type(1); }
  base_type& base() { return _rng; }
  const base_type& base() const { return _rng; }
  void reset() { }

  result_type operator()() {
    return result_type(_rng() - _rng.min()) * _factor;

  template<class CharT, class Traits>
  friend std::basic_ostream<CharT,Traits>&
  operator<<(std::basic_ostream<CharT,Traits>& os, const uniform_01& u)
    os << u._rng;
    return os;

  template<class CharT, class Traits>
  friend std::basic_istream<CharT,Traits>&
  operator>>(std::basic_istream<CharT,Traits>& is, uniform_01& u)
    is >> u._rng;
    return is;

  typedef typename base_type::result_type base_result;
  base_type _rng;
  result_type _factor;

//  A definition is required even for integral static constants
template<class UniformRandomNumberGenerator, class RealType>
const bool uniform_01<UniformRandomNumberGenerator, RealType>::has_fixed_range;

} // namespace boost