Shulou(Shulou.com)06/03 Report--

This article mainly introduces what is the use of the namespace namespace in CCompact +. It is very detailed and has a certain reference value. Friends who are interested must read it!

Overview

Namespaces (namespace) can help us distinguish functions, classes, variables with the same name in different libraries. The context is defined by using a namespace. A namespace defines a scope.

Namespace

In order to solve the naming conflicts between identifiers in C++ standard library and global identifiers in programs, as well as between all identifiers in different libraries. All identifiers of the standard C++ library are defined in a namespace named std. When the C++ standard library is used in the program, std is used as the limit.

We used the namespace (namespace) when we wrote "Hello World":

The role of namespaces

Namespaces are scopes introduced by ANSI C++ that can be named by users to deal with common conflicts of the same name in programs. In C++ programs, there are a large number of variables, functions and class names. If they all exist in the same global namespace, it will cause a lot of conflicts.

Custom function has the same name as standard library function.

The name used in the program is the same as the name in the third-party library

Name conflicts in different modules of the same project

Namespace mechanism that localizes the names declared in it:

The same name can be used in different contexts without causing name conflicts

The standard libraries in C++ are defined in the std namespace, reducing conflicts with user-defined names

Create your own namespace in your own program to avoid conflicts between localized names and the outside world

Custom namespace

We can define our own namespaces. We separate some global entities from other global entities by placing them in separate namespaces.

Format:

Namespace Namespace name {declare;}

Variables (can be initialized) and constants

Function (which can be defined or declared)

Structural body

Class

Template

Namespace (define another namespace in one namespace, that is, a nested namespace)

The role of namespaces is to establish separate scopes. Separate some global entities to avoid name conflicts.

Methods for namespace members

General method: when referencing a namespace member, qualify the namespace member with a namespace name to distinguish the identifier of the same name. (namespace:: namespace member name)

A mechanism to simplify the use of namespace members:

Use the namespace alias: namespace TV = Television; / / TV is equivalent to Television

Use format: using namespace member name using ns1::Student; / / Student is equivalent to ns1::Student

Use: using namespace Namespace name

Case

H2.h:

# ifndef PROJECT8_H1_H#define PROJECT8_H1_Hnamespace kitchen {class Table {private: int legs; int price; public: Table (int l, int p) {legs = l; price = p;}};} # endif / / PROJECT8_H1_H

H3.h:

# ifndef PROJECT8_H2_H#define PROJECT8_H2_Hnamespace office {class Table {private: int rows; int cols; public: Table (int r, int c) {rows = r; cols = c;}};} # endif / / PROJECT8_H2_H

Mian.cpp:

# include # include "h2.h" # include "h3.h" using namespace std;int main () {kitchen::Table T1 (6,300); office::Table T2 (6,2); return 0;} above is all the content of the article "what's the use of namespace namespace in Cannabash +". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.