如何将一个C ++ 11随机数生成器传递给一个函数？ [英] How do I pass a C++11 random number generator to a function?

问题描述

它们都继承自一个基类吗？我必须使用模板吗？

Do they all inherit from a base class? Do I have to use templates?

（我指的是这些http://www.codeguru.com/cpp/cpp/cpp_mfc/stl/article.php/c15319/ ）

我现在正在这样做：

typedef std::mt19937 RNG;

，然后

class Chooser {
public:
    Chooser(RNG& rng, uint n, uint min_choices, uint max_choices):

换句话说，我将引用传递给RNG。

In other words, I'm passing references to RNG. How would I pass in an arbitrary generator?

此外，我意识到这可能是一个不同的问题，但是如何将生成器传递给STL？

Also, I realize this is maybe a different question, but how do I pass the generator to STL?

std::random_shuffle(choices_.begin(), choices_.end(), rng);

似乎无效。

对传递生成器的解决方案：

solution to passing generator:

typedef std::ranlux64_base_01 RNG;
typedef std::mt19937 RNGInt;

解决方案传递给STL：

solution to passing to STL:

struct STL_RNG {
    STL_RNG(RNGInt& rng): gen(rng) {}       
    RNGInt& gen;
    int operator()(int n) { return std::uniform_int<int>(0, n)(gen); }
};

推荐答案

是一个有点意外），但它并不重要，因为这不是C ++函数如何工作。

They don't all inherit from a base (which is a little surprising), but it doesn't matter because that's not how C++ functors work.

对于任何一个给定类型的RNG，你得到正确的

For arbitrary RNGs of a single given type, you got it right as (now) posted.

如果您意味着，我如何定义一个接受任何随机数生成器作为参数的函数。

If you mean, how do I define a function which accepts any random number generator as an argument.

template< class RNG > // RNG may be a functor object of any type
int random_even_number( RNG &gen ) {
    return (int) gen() * 2;
}

您不需要使用任何更多的模板，因为类型扣除。

You don't need to use any more templates than this, because of type deduction.

定义一个函数来接受不同的RNG是棘手的，因为语义上需要一个共同的基本类型。您需要定义一个基本类型。

Defining one function to accept different RNG's is trickier because semantically that requires having a common base type. You need to define a base type.

struct RNGbase {
    virtual int operator() = 0;
    virtual ~RGNBase() {};
};

template< class RNG >
struct SmartRNG : RNGBase {
    RNG gen;

    virtual int operator() {
        return gen();
    }
};

int random_even_number( RNGBase &gen ) { // no template
    return (int) gen() * 2; // virtual dispatch
}

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