discrete_distribution 类

生成包含以等概率分布在每个区间中的等宽区间的离散型整数分布。

template<class IntType = int> class discrete_distribution { public:     // types     typedef IntType result_type;     struct param_type;     // constructor and reset functions     discrete_distribution();     template<class InputIterator>     discrete_distribution(InputIterator firstW, InputIterator lastW);     discrete_distribution(initializer_list<double> weightlist);     template<class UnaryOperation>     discrete_distribution(size_t count, double xmin, double xmax, UnaryOperation funcweight);     explicit discrete_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     vector<double> probabilities() const;     param_type param() const;     void param(const param_type& parm);     result_type min() const;     result_type max() const; };

参数

• IntType
  整数结果类型，默认为 int。 有关可能的类型，请参阅 <random>。

备注

此示例分布包含以等概率分布在每个区间中的等宽区间。 有关其他示例分布的信息，请参阅 piecewise_linear_distribution 类 和 piecewise_constant_distribution 类。

下表链接到有关各个成员的文章：

discrete_distribution::discrete_distribution	discrete_distribution::param
discrete_distribution::operator()	discrete_distribution::param_type

属性函数 vector<double> probabilities() 将返回每个生成的整数的各自概率。

有关分布类及其成员的详细信息，请参阅 <random>。

示例

 

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

using namespace std;

void test(const int s) {

    // uncomment to use a non-deterministic generator
    // random_device rd;
    // mt19937 gen(rd());
    mt19937 gen(1701);

    discrete_distribution<> distr({ 1, 2, 3, 4, 5 });

    cout << endl;
    cout << "min() == " << distr.min() << endl;
    cout << "max() == " << distr.max() << endl;
    cout << "probabilities (value: probability):" << endl;
    vector<double> p = distr.probabilities();
    int counter = 0;
    for (const auto& n : p) {
        cout << fixed << setw(11) << counter << ": " << setw(14) << setprecision(10) << n << endl;
        ++counter;
    }
    cout << endl;

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

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

int main()
{
    int samples = 100;

    cout << "Use CTRL-Z to bypass data entry and run using default values." << endl;
    cout << "Enter an integer value for the sample count: ";
    cin >> samples;

    test(samples);
}

输出

要求

标头：<random>

命名空间: std

请参见

参考

<random>