uniform_real_distribution 類別

在內含-專有的輸出範圍中產生統一 (每個值都有同等可能性) 浮點分佈。

template<class RealType = double> class uniform_real_distribution { public:     // types     typedef RealType result_type;     struct param_type;     // constructors and reset functions     explicit uniform_real_distribution(RealType a = 0.0, RealType b = 1.0);     explicit uniform_real_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     result_type a() const;     result_type b() const;     param_type param() const;     void param(const param_type& parm);     result_type min() const;     result_type max() const; };

參數

• RealType
  浮點結果類型，預設值為 double。 關於可能的類型，請參閱 <random>。

備註

此範本類別描述內含-專有分佈，其中透過分佈產生使用者指定的整數浮點類型的值，因此每個值都有同等可能性。 下表提供各個成員的文章連結。

uniform_real_distribution::uniform_real_distribution	uniform_real_distribution::a	uniform_real_distribution::param
uniform_real_distribution::operator()	uniform_real_distribution::b	uniform_real_distribution::param_type

屬性成員 a() 會傳回目前儲存的分佈下限，而 b() 會傳回目前儲存的上限。 對於此分佈類別，這些下限和上限值和一般屬性函式 min() 及 max() (敘述於 <random> 主題中) 所傳回的一樣。

如需分佈類別及其成員的詳細資訊，請參閱 <random>。

範例

 

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

void test(const double a, const double b, const int s) {

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

    std::uniform_real_distribution<> distr(a,b);

    std::cout << "lower bound == " << distr.a() << std::endl;
    std::cout << "upper bound == " << distr.b() << std::endl;

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

    // print results
    std::cout << "Distribution for " << s << " samples:" << std::endl;
    int counter = 0;
    for (const auto& elem : histogram) {
        std::cout << std::fixed << std::setw(11) << ++counter << ": " 
            << std::setprecision(10) << elem.first << std::endl;
    }
    std::cout << std::endl;
}

int main()
{
    double a_dist = 1.0;
    double b_dist = 1.5;

    int samples = 10;

    std::cout << "Use CTRL-Z to bypass data entry and run using default values." << std::endl;
    std::cout << "Enter a floating point value for the lower bound of the distribution: ";
    std::cin >> a_dist;
    std::cout << "Enter a floating point value for the upper bound of the distribution: ";
    std::cin >> b_dist;
    std::cout << "Enter an integer value for the sample count: ";
    std::cin >> samples;

    test(a_dist, b_dist, samples);
}

輸出

需求

標頭：<random>

命名空間: std

請參閱

參考

<random>