解析C++引用

#include <iostream.h>  
int main()  
{  
    int i = 10;   // A simple integer variable  
    int &j = i;   // A Reference to the variable i  
    j++;   // Incrementing j will increment both i and j.  
    // check by printing values of i and j  
    cout<<  i  <<  j  <<endl; // should print 11 11  
    // Now try to print the address of both variables i and j  
    cout<<  &i  <<  &j  <<endl;  
    // surprisingly both print the same address and make us feel that they are  
    // alias to the same memory location.  
    // In example below we will see what is the reality  
    return 0;  
}   

#include <iostream.h>  
int main()  
{  
    int i = 10;            // A simple integer variable  
    int *const j = &i;     // A Reference to the variable i  
    (*j)++;                // Incrementing j. Since reference variables are   
                          // automatically dereferenced by compiler  
    // check by printing values of i and j  
    cout<<  i  <<  *j  <<endl; // should print 11 11  
    // A * is appended before j because it used to be reference variable  
    // and it should get automatically dereferenced.  
    return 0;  
}  

#include <iostream.h>  
int main()  
{  
    int i = 10; // A Simple Integer variable  
    int &j = i; // A Reference to the variable  
    // Now we can also create a reference to reference variable.   
    int &k = j; // A reference to a reference variable  
    // Similarly we can also create another reference to the reference variable k  
    int &l = k; // A reference to a reference to a reference variable.  
    // Now if we increment any one of them the effect will be visible on all the  
    // variables.  
    // First print original values  
    // The print should be 10,10,10,10  
    cout<<  i  <<  ","  <<  j  <<  ","  <<  k  <<  ","  <<  l  <<endl;  
    // increment variable j  
    j++;   
    // The print should be 11,11,11,11  
    cout<<  i  <<  ","  <<  j  <<  ","  <<  k  <<  ","  <<  l  <<endl;  
    // increment variable k  
    k++;  
    // The print should be 12,12,12,12  
    cout<<  i  <<  ","  <<  j  <<  ","  <<  k  <<  ","  <<  l  <<endl;  
    // increment variable l  
    l++;  
    // The print should be 13,13,13,13  
    cout<<  i  <<  ","  <<  j  <<  ","  <<  k  <<  ","  <<  l  <<endl;  
    return 0;  
}  

#include <iostream.h>  
int main()  
{  
    int i = 10;         // A Simple Integer variable  
    int *const j = &i;     // A Reference to the variable  
    // The variable j will hold the address of i  
    // Now we can also create a reference to reference variable.   
    int *const k = &*j;     // A reference to a reference variable  
    // The variable k will also hold the address of i because j   
    // is a reference variable and   
    // it gets auto dereferenced. After & and * cancels each other   
    // k will hold the value of  
    // j which it nothing but address of i  
    // Similarly we can also create another reference to the reference variable k  
    int *const l = &*k;     // A reference to a reference to a reference variable.  
    // The variable l will also hold address of i because k holds address of i after  
    // & and * cancels each other.  
    // so we have seen that all the reference variable will actually holds the same  
    // variable address.  
    // Now if we increment any one of them the effect will be visible on all the  
    // variables.  
    // First print original values. The reference variables will have * prefixed because   
    // these variables gets automatically dereferenced.  
    // The print should be 10,10,10,10  
    cout<<  i  <<  ","  <<  *j  <<  ","  <<  *k  <<  ","  <<  *l  <<endl;  
    // increment variable j  
    (*j)++;   
    // The print should be 11,11,11,11  
    cout<<  i  <<  ","  <<  *j  <<  ","  <<  *k  <<  ","  <<  *l  <<endl;  
    // increment variable k  
    (*k)++;  
    // The print should be 12,12,12,12  
    cout<<  i  <<  ","  <<  *j  <<  ","  <<  *k  <<  ","  <<  *l  <<endl;  
    // increment variable l  
    (*l)++;  
    // The print should be 13,13,13,13  
    cout  <<  i  <<  ","  <<  *j  <<  ","  <<  *k  <<  ","  <<  *l  <<endl;  
    return 0;  
}  

#include <iostream.h>  
class Test  
{  
    int &i;   // int *const i;  
    int &j;   // int *const j;  
    int &k;   // int *const k;   
};  
int main()  
{      
    // This will print 12 i.e. size of 3 pointers  
    cout<<  "size of class Test = "  <<   sizeof(class Test)  <<endl;  
    return 0;  
}  

#include <iostream.h>  
class A  
{  
public:  
         virtual void print() { cout<<"A.."<<endl; }  
};  
class B : public A  
{  
public:  
         virtual void print() { cout<<"B.."<<endl; }  
};  
   
class C : public B  
{  
public:  
         virtual void print() { cout<<"C.."<<endl; }  
};  
int main()  
{  
         C c1;  
         A &a1 = c1;  
         a1.print(); // prints C  
         A a2 = c1;  
         a2.print(); // prints A  
         return 0;  
}