Single and Double colons in C ++

Single and Double colons in C ++

1. colon (:) usage
 
(1) represents the definition of the intra-organization bit domain (that is, the variable occupies several bit spaces)
 
Typedef struct _ XXX {
 
Unsigned char A: 4;
 
Unsigned char C;
 
}; XXX
 
(2) The colon following the constructor acts as a segmentation function. It is a class-based method for assigning values to member variables. The initialization list is more suitable for the constant const type of member variables.
 
Struct _ XXX {
 
_ XXX (): Y (0xc0 ){}
 
};
 
(3) The colons after public: and private: indicate that all the Members defined later are public or private until the next "public:" or "Private:" appears. "Private:" is the default processing.
 
(4) the class name is followed by the colon to define the inheritance of the class.
 
Class derived class name: Inheritance Method Base Class Name
 
{
 
Member of the derived class
 
};
 
Inheritance Method: public, private, and protected. The default process is public.
 
2. Double colon (: :) usage
 
(1) "domain operator"
 
For example, a Class A is declared, and Class A declares a member function void F (), but the definition of F is not given in the class declaration, when F is defined outside the class,

Void A: F () indicates that the F () function is a member function of Class.
 
(2) It is used directly before the global function to indicate that it is a global function.

For example, in VC, you can add ::
 
(3) Reference member functions and variables, and scope member operators
 
For example, system: Math: SQRT () is equivalent to system. Math. SQRT ()