Introduction to namespace Basics

In cooperative programming with others , Naming conflicts may occur . And the bigger the project , The more trouble the naming conflict causes .

So is there any way that we can use the same name without using conflict , Here is to introduce C++ In grammar namespace Namespace .

Catalog

One . Basic usage

​ Two . Standard library

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One . Basic usage

namespace Namespaces can store variables , Structure , Function, etc. . When using, we need to define namespace To declare .

For example, we want to define two functions car, It also needs to be called in the same main function , Then you can define two namespace To store these two functions separately . Directly call... In the main function namespace that will do

call namespace We need to use the scope symbol (::). For example, in the following program , When we want to use BYD Of car when , Just call in the main function BYD::car() that will do . This is equivalent to telling the computer , When it sees :: The symbol , It needs to be in BYD This namespace Find car function . Don't look for other places , Not if you find it .

Functions can be defined directly in the namespace namespace Directly in , Of course , It can also be defined outside the domain like the following program . At this time , When defining functions , Call the namespace first , Let the computer know that I want to define something namespace The function in .

  Two . Standard library

Using the standard library std When , We have three calling methods .

One , Is used every time a standard library function is called std::.

Two , Is to define the standard library for global use , That is to say in the header using namespace std; .

 

  The first method is too cumbersome , The second definition is global and may cause conflict , Then we can use the third definition method .

3、 ... and , Define high-frequency objects as global use . namely using std:: object .

 

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