公有成員函式 (public member function)
<random>
| (1) | template<class URNG>result_type operator()(URNG& g); |
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| (2) | template<class URNG>result_type operator()(URNG& g, const param_type& parm); |
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生成隨機數
返回一個遵循物件關聯的分佈引數（版本1）或由parm指定的引數（版本2）的新的隨機數。
生成器物件（g）透過其operator()成員函式。離散分佈物件會轉換由此獲取的值，以便在呼叫此成員函式時，使用相同的引數會產生遵循離散分佈的值，並具有其可能值的適當權重。
引數
- g
- 一個均勻隨機數生成器物件，用作隨機性源。
URNG應為均勻隨機數生成器型別，例如標準生成器類之一。
- parm
- 代表分佈引數（權重）的物件，透過呼叫成員函式 param 獲取。
param_type是一個成員型別。
返回值
A new random number. （一個新的隨機數。）
result_type是一個成員型別，定義為第一個類模板引數的別名 (IntType).
示例
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// discrete_distribution example
#include <iostream>
#include <chrono>
#include <random>
int main()
{
// construct a trivial random generator engine from a time-based seed:
unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
std::default_random_engine generator (seed);
// in a regular die, every number is equally likely:
std::uniform_int_distribution<int> regular_die (1,6);
// in this loaded die, the 6 is three times more likely:
std::discrete_distribution<int> loaded_die {0,1,1,1,1,1,3};
int regular_score = 0;
int loaded_score = 0;
for (int i=0; i<1000; ++i) {
int regular_roll = regular_die(generator);
int loaded_roll = loaded_die(generator);
if (regular_roll<loaded_roll) ++loaded_score;
else if (regular_roll>loaded_roll) ++regular_score;
}
std::cout << "after 1000 experiments:" << std::endl;
std::cout << "regular die won: " << regular_score << " times." << std::endl;
std::cout << "loaded die won: " << loaded_score << " times." << std::endl;
std::cout << "ties: " << (1000-regular_score-loaded_score) << std::endl;
return 0;
}
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可能的輸出
after 1000 experiments:
regular die won: 299 times.
loaded die won: 540 times.
ties: 161
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