What does :: mean in c++

Scope resolution operator:: is used to specify the scope of the identifier and access members in the scope, including: accessing global variables and functions, accessing class members, and accessing static members. Avoid excessive use of::, to keep the code readable and maintainable.

The meaning of :: in C

In C, :: is called Scope resolution operator. It is used to specify the scope of an identifier and access members in that scope.

Function:

• Access global variables and functions:Required when referencing global variables or functions outside a function or class Use :: to declare its global scope. For example:

<code class="cpp">int global_variable = 0;

void function() {
  ::global_variable++;  // 访问全局变量
}</code>

• Accessing class members: You can use :: outside the class to access the member variables or member functions of the class. For example:

<code class="cpp">class MyClass {
public:
  int member_variable;
};

int main() {
  MyClass::member_variable = 10;  // 访问类成员变量
}</code>

• Accessing static members: You can also use :: to access static members of a class, even if no object of the class is created. For example:

<code class="cpp">class MyClass {
public:
  static int static_variable;
};

int MyClass::static_variable = 10;  // 声明静态成员变量

int main() {
  ::MyClass::static_variable++;  // 访问静态成员变量
}</code>

Notes:

• The compiler will interpret:: as global scope: If in scope If the identifier is not declared in the scope, the compiler will interpret :: as global scope. For example:

<code class="cpp">int x = 10;

void function() {
  ::x++;  // 访问全局变量 x
}</code>

• Don’t overuse :::Overuse of :: should be avoided as it can make the code difficult to read and maintain. Typically, use :: only when you explicitly need to access global or static members.

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