26 Numerics library [numerics]

26.5 Random number generation [rand]

26.5.8 Random number distribution class templates [rand.dist] Poisson distributions [rand.dist.pois] Class template exponential_distribution [rand.dist.pois.exp]

An exponential_distribution random number distribution produces random numbers x > 0 distributed according to the probability density function p(x | λ) = λ ex .

template<class RealType = double>
 class exponential_distribution{
 // types
 typedef RealType result_type;
 typedef unspecified param_type;

 // constructors and reset functions
 explicit exponential_distribution(RealType lambda = 1.0);
 explicit exponential_distribution(const param_type& parm);
 void reset();

 // generating functions
 template<class URNG>
   result_type operator()(URNG& g);
 template<class URNG>
   result_type operator()(URNG& g, const param_type& parm);

 // property functions
 RealType lambda() const;
 param_type param() const;
 void param(const param_type& parm);
 result_type min() const;
 result_type max() const;

explicit exponential_distribution(RealType lambda = 1.0);

Requires: 0 < lambda .

Effects: Constructs a exponential_distribution object; lambda corresponds to the parameter of the distribution.

RealType lambda() const;

Returns: The value of the lambda parameter with which the object was constructed.