Double colon action in C + +

1.

Scope symbol:: The front of the general is the class name, followed by the class is generally the member name, C + + as an example to avoid different classes have the same name of the member and the scope of the way to differentiate
For example: A, B represents two classes, and a member is member in a A, B. So
A::member represents a member of Class A member
B::member represents a member in Class B member

2.

Global scope Symbol:

For example:

#include <stdio.h>int count = 0; Global variable 0void main () {  int count = 10;//local variable  of printf ("Count =%d\n", count);//local variable masks global variable so the output is ten {  int Count =;    printf ("Count =%d\n",:: Count); Scope symbol indicates reference global variable 0  //::sort}}

As a global scope symbol, double colons are placed at the beginning. This is similar to the file path under Linux, where "/" is placed at the beginning to represent an absolute path, and is placed in the middle to represent a subdirectory.

:: A symbol can specify either a class or a variable and a namespace:

If a function is placed globally, the global function is the global namespace if the variable is defined globally, if a namespace is placed globally.

3.

另外，双冒号也常常用于在类变量内部作为当前类实例的元素进行表示：

Class CA {public:  int ca_var;  int add (int a, int b);  int add (int a);}; scope int Ca::add (int a, int b) {  return a + B;}//In addition, a double colon is represented inside a class variable as an element of the current class instance int ca::add (int a) {  return a +:: Ca_var ;} Represents a variable in the current class instance Ca_var

Double colon action in C + +