B is inherited from a. pointer A cannot be implicitly converted to pointer B. function parameters only support pointer type and are irrelevant to objects actually pointed.

# Include
<Iostream>

# Include
<String>

 

Using namespace STD;

 

Class

{};

 

Class B:
Public

{};

 

Void F (B & B)

{

Cout <"F (B & B)" <Endl;

}

Void F (A &)

{

Cout <"F (A & A)" <Endl;

}

 

Int _ tmain (INT argc, _ tchar * argv [])

{

A * P1 = new B;

F (* P1); // call f (A &)

 

A;

B * P2 = (B *) &;

F (* P2); // call f (B & B)

 

/* F (* P2) Call analysis: F (B & B) is equivalent to F (B * P), F (A & A) is equivalent to F (A * P ),

F (* P2) is equivalent to F (P2), while P2 is B * type. Of course, F (B * P) is called, that is, F (B & B) is called ).

The same applies to F (* P1.

It can be seen that the parameter type should be matched, regardless of the object actually pointed to (function parameters only support the pointer type ). */

 

System ("pause ");

Return 0;

}

 

However, if there is no void F (A & A) function, that is:

Class

{};

 

Class B:
Public

{};

 

Void F (B & B)

{

Cout <"F (B & B)" <Endl;

}

Int _ tmain (INT argc, _ tchar * argv [])

{

A * P1 = new B;

F (* P1); // compilation error. A * cannot be implicitly converted to B *. F (A * P) is supposed to be called, but only F (B * P) is required, and a * cannot be implicitly converted to B *. Therefore, F (B * P) is not called ), error.

 

System ("pause ");

Return 0;

}