实现一个std ::阵列像一个C ++ 11 initializer_list容器 [英] Implementing a std::array-like container with a C++11 initializer_list

问题描述

的std ::阵列的唯一和国际海事组织非常不方便需要注意的是，它不能从初始化列表推断其大小如内置的C数组，它的大小必须为模板进行传递。

是否有可能实现一个std ::阵列状的容器（大约瘦包装一个内建C数组）以 C ++ 11 initializer_list <？ / p>

我问，因为，不同的std ::阵列，它会自动推断从初始化列表的数组这是很多更方便的大小。例如：

  // il_array是假想的容器
//自动从initalizer名单推断其大小
il_array＆LT; INT＆GT; myArr，该= {2，4，6，7，8};
 

我们也想提供一个构造函数，如果没有提供一个初始化列表来指定大小。例如：

  //构造大小为10的一个固定大小的数组
il_array＆LT; INT＆GT; myarr2（10）;
 

这也会使容器如其他标准集装箱更加一致向量，双端队列和列表。

据我所知这是不可能的包裹C-阵列例如ŧelems [尺寸]，必须有固定的大小和initializer_list的大小（）成员函数不是恒定的。

另外，我想知道是否有可能使用的是可变参数模板来实现这样的容器，虽然从我读过，我不认为这是可能的。

解决方案

我觉得你的运气了这里。的std ::阵列的很大的优点是，它是一个POD和可以静态初始化。

如果你有一个构造函数接受一个std :: initializer_list的容器，它必须复制值（除非它仅仅是一个恒定的参考初始化，这是不是非常有用）。

The only and imo very inconvenient caveat of std::array is that it can't deduce its size from the initializer list like built-in C arrays, it's size must be passed as a template.

Is it possible to implement a std::array-like container (a thin wrapper around a built-in C array) with a C++11 initializer_list?

I ask because, unlike std::array, it would automatically deduce the size of the array from the initializer list which is a lot more convenient. For example:

// il_array is the hypothetical container
// automatically deduces its size from the initalizer list 
il_array <int> myarr = {2, 4, 6, 7, 8}; 

We would also want to provide a constructor to specify the size if an initializer list was not provided. For example:

// construct a fixed size array of size 10
il_array <int> myarr2 (10); 

This would also make the container more consistent with the other standard containers e.g. vector, deque and list.

To the best of my knowledge it isn't possible as the wrapped C-array e.g. T elems [size], must have constant size and initializer_list's size() member function isn't constant.

Also, I was wondering if was possible to implement such a container using a variadic template although from what I've read I don't think it's possible.

解决方案

I think you are out of luck here. The great advantage of std::array is that it is a POD and can be statically initialized.

If you have a container with a constructor taking a std::initializer_list, it would have to copy the values (unless it is just a constant reference to the initializer, which isn't very useful).

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