cppdraft_translate/cppdraft/rand/dist/pois/exp.md

[rand.dist.pois.exp]

29 Numerics library [numerics]

29.5 Random number generation [rand]

29.5.9 Random number distribution class templates [rand.dist]

29.5.9.4 Poisson distributions [rand.dist.pois]

29.5.9.4.2 Class template exponential_distribution [rand.dist.pois.exp]

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An exponential_distribution random number distribution produces random numbers x>0 distributed according to the probability density function in Formula 29.9.

p(x|λ)=λe−λx(29.9)

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namespace std {templateclass exponential_distribution {public:// typesusing result_type = RealType; using param_type = unspecified; // constructors and reset functions exponential_distribution() : exponential_distribution(1.0) {}explicit exponential_distribution(RealType lambda); explicit exponential_distribution(const param_type& parm); void reset(); // equality operatorsfriend bool operator==(const exponential_distribution& x, const exponential_distribution& y); // generating functionstemplate result_type operator()(URBG& g); template result_type operator()(URBG& 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; // inserters and extractorstemplate<class charT, class traits>friend basic_ostream<charT, traits>&operator<<(basic_ostream<charT, traits>& os, const exponential_distribution& x); template<class charT, class traits>friend basic_istream<charT, traits>&operator>>(basic_istream<charT, traits>& is, exponential_distribution& x); };}

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explicit exponential_distribution(RealType lambda);

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Preconditions: 0<lambda.

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Remarks: lambda corresponds to the parameter of the distribution.

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RealType lambda() const;

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