What is a namespace?

What is a namespace?

Namespace is also called namespace, namespace, etc. It represents the visible range of an identifier (identifier). An identifier can be defined in multiple namespaces, and its meaning in different namespaces is irrelevant.

In this way, any identifier can be defined in a new namespace, and they will not conflict with any existing identifiers, because the existing definitions are in other namespaces.

For example, suppose Bill is an employee of Company X and his job number is 123, and John is an employee of Company Y and his job number is also 123. Since two people work in different companies, they can use the same job number to identify them without causing confusion. Here, each company represents an independent name space. If two people work for the same company, their job numbers cannot be the same, otherwise there will be confusion when paying wages.

This feature is the main reason for using namespaces. In large computer programs or documents, there are often hundreds or thousands of identifiers. Namespaces provide a mechanism for hiding locale identifiers. By organizing logically related identifiers into corresponding namespaces, the entire system can be made more modular.

In programming languages, namespace is a special abstraction of scope. It contains identifiers within the scope and is itself represented by an identifier, thus converting a series of Logically related identifiers are grouped together using an identifier.

Many modern programming languages ​​support namespaces. In some programming languages ​​(such as C and Python), the identifier of the namespace itself also belongs to an outer namespace, that is, the namespace can be nested to form a namespace tree, and the root of the tree is the unnamed global namespace. .

The scope of functions and classes can be regarded as implicit namespaces, which are inextricably linked to visibility, accessibility, and object lifecycle.

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