“CopyConstructible”需要C ++ stl容器元素 [英] "CopyConstructible" requirement for C++ stl container element

问题描述

关于对C ++ stl容器元素的要求，标准说：元素类型应该是CopyConstructible，并且有一个表用于CopyConstructible需求。还有各种书（Josuttis等），生成的副本应该是等同于源。

Regarding to the requirement for C++ stl container element, the standard says: the element type should be CopyConstructible, and there is a table for CopyConstructible requirements. Also by various books (Josuttis, etc.), the generated copy should be "equivalent to" the source.

我想我需要一些清楚。什么是等同于？另外，我有点困惑的CopyConstructible和深/浅拷贝之间的关系。通常，复制构造函数是浅复制或深复制。那么哪一个适用于CopyConstructible，哪一个不适用？

I think I need some clarity here. What is exactly "equivalent to"? Also I am a bit confused with the relation between the "CopyConstructible" and the "deep/shallow copy". In general, a copy constructor is either shallow copy or deep copy. So which one applies to the "CopyConstructible", and which does not?

感谢任何意见！

推荐答案

深或浅拷贝都工作。例如， shared_ptr 总是做一个浅拷贝（有一些额外的引用计数的东西），你可以在容器中使用它们很好。这取决于复制操作的语义。

Deep or shallow copy both work. For instance, shared_ptr always does a shallow copy (with some extra reference counting stuff), and you can use them in containers just fine. It depends on the semantics of copy-operation.

等效意味着您的程序不应该依赖于它是与原件还是与副本一起工作。

Equivalent means your program should not depend on whether it works with the original or with the copy.

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