bernoulli_distribution 類別

產生白努利 (Bernoulli) 分佈。

class bernoulli_distribution { public:     // types     typedef bool result_type;     struct param_type;     // constructors and reset functions     explicit bernoulli_distribution(double p = 0.5);     explicit bernoulli_distribution(const param_type& parm);     void reset();     // generating functions     template<class URNG>     result_type operator()(URNG& gen);     template<class URNG>     result_type operator()(URNG& gen, const param_type& parm);     // property functions     double p() const;     param_type param() const;     void param(const param_type& parm);     result_type min() const;     result_type max() const; };

備註

此類別描述產生類型 bool 的值的分佈，此分佈是根據白努利分佈離散可能性函式進行分佈。 下表提供各個成員的文章連結。

bernoulli_distribution::bernoulli_distribution	bernoulli_distribution::p	bernoulli_distribution::param
bernoulli_distribution::operator()		bernoulli_distribution::param_type

屬性成員 p() 會傳回目前儲存的分佈參數值 p。

如需分佈類別及其成員的詳細資訊，請參閱 <random>。

如需白努利分佈的詳細資訊，請參閱 Wolfram MathWorld 文章白努利分佈 (英文)。

範例

 

// compile with: /EHsc /W4
#include <random> 
#include <iostream>
#include <iomanip>
#include <string>
#include <map>

void test(const double p, const int s) {

    // uncomment to use a non-deterministic seed
    //    std::random_device rd;
    //    std::mt19937 gen(rd());
    std::mt19937 gen(1729);

    std::bernoulli_distribution distr(p);

    std::cout << "p == " << distr.p() << std::endl;

    // generate the distribution as a histogram
    std::map<bool, int> histogram;
    for (int i = 0; i < s; ++i) {
        ++histogram[distr(gen)];
    }

    // print results
    std::cout << "Histogram for " << s << " samples:" << std::endl;
    for (const auto& elem : histogram) {
        std::cout << std::boolalpha << std::setw(5) << elem.first << ' ' << std::string(elem.second, ':') << std::endl;
    }
    std::cout << std::endl;
}

int main()
{
    double p_dist = 0.5;
    int samples = 100;

    std::cout << "Use CTRL-Z to bypass data entry and run using default values." << std::endl;
    std::cout << "Enter a double value for p distribution (where 0.0 <= p <= 1.0): ";
    std::cin >> p_dist;
    std::cout << "Enter an integer value for a sample count: ";
    std::cin >> samples;

    test(p_dist, samples);
}

輸出

Use CTRL-Z to bypass data entry and run using default values.
Enter a double value for p distribution (where 0.0 <= p <= 1.0): .45
Enter an integer value for a sample count: 100
p == 0.45
Histogram for 100 samples:
false :::::::::::::::::::::::::::::::::::::::::::::::::::::
 true :::::::::::::::::::::::::::::::::::::::::::::::

需求

標頭：<random>

命名空間: std

請參閱

參考

<random>