:std::string和std::string有什么区别?

what is the difference between ::std::string and std::string The former is global? But global for what?Is not namespace std global? Thanks for helping me.

::std::string和std::string之间的区别是什么?但全球为了什么?名称空间std不是全局的吗?谢谢你帮助我。

1 个解决方案

#1

::std::string means string in namespace std in the global namespace. The leading :: forces the lookup to start in the global namespace. Therefore ::std::string always means the string type from the C++ standard library.

:::string表示全局名称空间中的名称空间std中的string。引导::强制查找在全局命名空间中启动。因此::std::string总是表示来自c++标准库的string类型。

std::string means string in namespace std, where std will be looked up in the current scope. Therefore, if there is a class, namespace, or enum named std, name lookup might find that std.

string表示命名空间std中的string，其中std将在当前范围中查找。因此，如果有一个类、名称空间或枚举名为std，那么名称查找可能会发现std。

#include <string>
namespace foo {
  namespace std {
    class string { ... };
    namespace bar {
      std::string s;    // means foo::std::string
      ::std::string s;  // means string from standard library
    }
  }
}

It is not necessary to use the leading :: as long as you and your collaborators agree to not name anything std. It's just good style.

只要你和你的合作者同意不要说出任何std的名字，那就不是必要的了。

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