为什么std :: allocator在C ++ 17中丢失成员类型/函数？

问题描述：

在查看 std :: allocator 时，我看到了以下成员：
value_type ，
指针，
const_pointer ，
引用，
const_reference ，
size_type ，
difference_type 和
rebind 已全部弃用。

While looking at std::allocator, I see that members:
value_type, pointer, const_pointer, reference, const_reference, size_type, difference_type, and rebind have all been deprecated.

分配者也将不再具有成员：

地址， max_size ，构造或破坏。

Allocators will also no longer have the members:
address, max_size, construct, or destroy.

为什么会这样？

答

如果您查看相关的isocpp论文，您会发现现在想到的是您提到的第一个论文集最好放在 std :: allocator_traits 。自从STL（甚至不是标准库）问世以来，使用特征的转移就更多了。

If you look at the relevant isocpp paper you can see that the first set you mention is now thought to be better placed in std::allocator_traits. Since the STL (not even standard library) came out, there's been more of a shift to use traits.

重新绑定也是遗物。首次发布STL时，不支持别名和模板模板参数。有了这些语言功能， rebind 似乎相当复杂。例如，如您在中看到的那样，在《 The C ++ Programming Language》，第4版，第34.4.1节，p 998，注释默认分配程序类中的经典重新绑定成员：

rebind is also a relic. When the STL first came out, aliases and template-template parameters were not supported. With these language features in existence, rebind seems fairly convoluted. E.g., as you can see in an answer to this question, in The C++ Programming Language, 4th edition, section 34.4.1, p. 998, commenting the 'classical' rebind member in default allocator class :

template<typename U>
     struct rebind { using other = allocator<U>;};

Bjarne Stroustupr写道：好奇的重新绑定模板是一个古老的别名。应该是：

Bjarne Stroustupr writes this : "The curious rebind template is an archaic alias. It should have been:

template<typename U>
using other = allocator<U>;

但是，分配器是在C ++支持此类别名之前定义的。

However, allocator was defined before such aliases were supported by C++."

总的来说，这是赶上语言和范式转变的标准库。

So, altogether, it's the standard library catching up with the language and paradigm shifts.

为什么std :: allocator在C ++ 17中丢失成员类型/函数？

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