What is the meaning of prepended double colon “::” in C++?
The prepended double colon is also known as the scope resolution operator. Some of the uses of this operator are given as follows.
Define a function outside a class
The scope resolution operator can be used to define a function outside a class. A program that demonstrates this is given as follows.
Example
Live Demo
#include<iostream>
using namespace std;
class Example {
int num;
public:
Example() {
num = 10;
}
void display();
};
void Example::display() {
cout << "The value of num is: "<<num;;
}
int main() {
Example obj;
obj.display();
return 0;
}Output
The output of the above program is as follows.
The value of num is: 10
Access a global variable when there is also a local variable with the same name
The scope resolution operator can be used to access a global variable when there is also a local variable with the same name. A program that demonstrates this is given as follows.
Example
Live Demo
#include<iostream>
using namespace std;
int num = 7;
int main() {
int num = 3;
cout << "Value of local variable num is: " << num;
cout << "\nValue of global variable num is: " << ::num;
return 0;
}Output
The output of the above program is as follows.
Value of local variable num is: 3
Value of global variable num is: 7
Published on 21-Nov-2018 16:47:56
