“使用命名空间标准"有什么用? [英] What is the use of "using namespace std"?

问题描述

using namespace std有什么用?

我希望看到通俗易懂的解释.

I'd like to see explanation in Layman terms.

推荐答案

• 使用:您将使用它.
• 命名空间:使用什么?命名空间.
• std:std 命名空间(C++ 标准库的特性，例如 string 或 vector, 被声明).
• using: You are going to use it.
• namespace: To use what? A namespace.
• std: The std namespace (where features of the C++ Standard Library, such as string or vector, are declared).

写完这条指令后，如果编译器看到string，它就会知道你可能指的是std::string，如果它看到vector，它会知道你可能指的是std::vector.(当然，前提是您在编译单元中包含了定义它们的头文件.)

After you write this instruction, if the compiler sees string it will know that you may be referring to std::string, and if it sees vector, it will know that you may be referring to std::vector. (Provided that you have included in your compilation unit the header files where they are defined, of course.)

如果你不写它，当编译器看到string或vector时它不会知道你指的是什么.你需要明确告诉它 std::string 或 std::vector，如果你不这样做，你会得到一个编译错误.

If you don't write it, when the compiler sees string or vector it will not know what you are refering to. You will need to explicitly tell it std::string or std::vector, and if you don't, you will get a compile error.

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