散列指针作为C ++ STL中unordered_map的键 [英] Hashing pointers as Keys for unordered_map in C++ STL

问题描述

我发布了一个类似的关于使用指针作为Keys on C ++ STL中的地图。用作Keys时，指针在unordered_maps中的散列方式如何。更具体地说，如果我定义：

  std :: unordered_map< CustomClass *，int> FOO; 
  

默认的C ++ std :: hash实现是否可以处理这些指针？使用安全吗？这是一个很好的做法吗？

std :: hash< T *> 被定义，但它如何操作的细节取决于实现。它肯定是安全的使用，我认为这是一个好习惯 - 只要它是你需要的指针作为关键，而不是对象内容本身。

I posted a similar quetion regarding using pointers as Keys on maps in C++ STL. How are pointers hashed in unordered_maps when used as Keys. More specifically if I define:

std::unordered_map< CustomClass*, int > foo;

Would the default C++ std::hash implementation work to handle these pointers? Is it safe to use? Is this good practice?

解决方案

std::hash<T*> is defined but the details of how it operates are implementation dependent. It will certainly be safe to use, and I'd consider it good practice - as long as it's the pointer you need as the key, and not the object contents itself.

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