Boost C++ Libraries

...one 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 a snapshot of the master branch, built from commit dd85cafccc.
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Class template exponential_distribution

boost::random::exponential_distribution

Synopsis

// In header: <boost/random/exponential_distribution.hpp>

template<typename RealType = double> 
class exponential_distribution {
public:
  // types
  typedef RealType input_type; 
  typedef RealType result_type;

  // member classes/structs/unions

  class param_type {
  public:
    // types
    typedef exponential_distribution distribution_type;

    // construct/copy/destruct
    param_type(RealType = 1.0);

    // public member functions
    RealType lambda() const;

    // friend functions
    template<typename CharT, typename Traits> 
      friend std::basic_ostream< CharT, Traits > & 
      operator<<(std::basic_ostream< CharT, Traits > &, const param_type &);
    template<typename CharT, typename Traits> 
      friend std::basic_istream< CharT, Traits > & 
      operator>>(std::basic_istream< CharT, Traits > &, const param_type &);
    friend bool operator==(const param_type &, const param_type &);
    friend bool operator!=(const param_type &, const param_type &);
  };

  // construct/copy/destruct
  explicit exponential_distribution(RealType = 1.0);
  explicit exponential_distribution(const param_type &);

  // public member functions
  RealType lambda() const;
  RealType min() const;
  RealType max() const;
  param_type param() const;
  void param(const param_type &);
  void reset();
  template<typename Engine> result_type operator()(Engine &) const;
  template<typename Engine> 
    result_type operator()(Engine &, const param_type &) const;

  // friend functions
  template<typename CharT, typename Traits> 
    friend std::basic_ostream< CharT, Traits > & 
    operator<<(std::basic_ostream< CharT, Traits > &, 
               const exponential_distribution &);
  template<typename CharT, typename Traits> 
    friend std::basic_istream< CharT, Traits > & 
    operator>>(std::basic_istream< CharT, Traits > &, 
               const exponential_distribution &);
  friend bool operator==(const exponential_distribution &, 
                         const exponential_distribution &);
  friend bool operator!=(const exponential_distribution &, 
                         const exponential_distribution &);
};

Description

The exponential distribution is a model of random distribution with a single parameter lambda.

It has

The implementation uses the "ziggurat" algorithm, as described in

"The Ziggurat Method for Generating Random Variables", George Marsaglia and Wai Wan Tsang, Journal of Statistical Software Volume 5, Number 8 (2000), 1-7.

exponential_distribution public construct/copy/destruct

  1. explicit exponential_distribution(RealType lambda = 1.0);

    Constructs an exponential_distribution with a given lambda.

    Requires: lambda > 0

  2. explicit exponential_distribution(const param_type & param);

    Constructs an exponential_distribution from its parameters

exponential_distribution public member functions

  1. RealType lambda() const;

    Returns the lambda parameter of the distribution.

  2. RealType min() const;

    Returns the smallest value that the distribution can produce.

  3. RealType max() const;

    Returns the largest value that the distribution can produce.

  4. param_type param() const;

    Returns the parameters of the distribution.

  5. void param(const param_type & param);

    Sets the parameters of the distribution.

  6. void reset();

    Effects: Subsequent uses of the distribution do not depend on values produced by any engine prior to invoking reset.

  7. template<typename Engine> result_type operator()(Engine & eng) const;

    Returns a random variate distributed according to the exponential distribution.

  8. template<typename Engine> 
      result_type operator()(Engine & eng, const param_type & param) const;

    Returns a random variate distributed according to the exponential distribution with parameters specified by param.

exponential_distribution friend functions

  1. template<typename CharT, typename Traits> 
      friend std::basic_ostream< CharT, Traits > & 
      operator<<(std::basic_ostream< CharT, Traits > & os, 
                 const exponential_distribution & ed);

    Writes the distribution to a std::ostream.

  2. template<typename CharT, typename Traits> 
      friend std::basic_istream< CharT, Traits > & 
      operator>>(std::basic_istream< CharT, Traits > & is, 
                 const exponential_distribution & ed);

    Reads the distribution from a std::istream.

  3. friend bool operator==(const exponential_distribution & lhs, 
                           const exponential_distribution & rhs);

    Returns true iff the two distributions will produce identical sequences of values given equal generators.

  4. friend bool operator!=(const exponential_distribution & lhs, 
                           const exponential_distribution & rhs);

    Returns true iff the two distributions will produce different sequences of values given equal generators.


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