C++ 引用 （by-reference variable）

 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 int main(){
 5     int a = 10;
 6     int b = 20;
 7     int &rn = a;
 8     int equal;
 9     
10     rn = b;
11     cout<<"a="<<a<<endl;  //20
12     cout<<"b="<<b<<endl;  //20
13     
14     rn = 100;
15     cout<<"a="<<a<<endl;  //100
16     cout<<"b="<<b<<endl;  //20
17     
18     equal = (&a==&rn)?1:0; //1
19     cout<<"equal="<<equal<<endl;
20     return 0;
21 }

a = 20
b = 20
a = 100
b = 20
equal = 1

 1 #include <iostream>
 2 using namespace std;
 3 int main(){
 4     int a = 1;
 5     int b = 10;
 6     int* p = &a;
 7     int* &pa = p;
 8     
 9     (*pa)++;
10     cout<<"a="<<a<<endl;   //2
11     cout<<"b="<<b<<endl;   //10
12     cout<<"*p="<<*p<<endl; //2
13     
14     pa = &b;
15     (*pa)++;
16     cout<<"a="<<a<<endl;   //2
17     cout<<"b="<<b<<endl;   //11
18     cout<<"*p="<<*p<<endl; //11
19     return 0;
20 }

 1 #include <iostream>
 2 using namespace std;
 3 int main(){
 4     int a = 1,b = 2;
 5     int &c;      // 引用在声明时要初始化
 6     int &d = a;
 7     &d = b;      // 引用只能在声明的时候被赋值，以后都不能再把该应用作为其他变量名的别名
 8     int *p;
 9     *p = 5;      //p没有被初始化，为野指针，对野指针赋值会导致程序运行时崩溃
10     return 0;
11 }

 1 #include <iostream>
 2 using namespace std;
 3 void swap(char* &x, char* &y){
 4     char *temp;
 5     temp = x;
 6     x = y;
 7     y = temp;
 8 }
 9 int main(){
10     char *ap = "hello";
11     char *bp = "how are you?";
12     
13     cout<<"*ap":<<ap<<endl;
14     cout<<"*bp:"<<bp<<endl;
15     swap(ap,bp);
16     cout<<"*ap:"<<ap<<endl;
17     cout<<"*bp:">>bp<<endl;
18     return 0;
19 }

*ap: hello 
*bp: how are you?
*ap: how are you?
*bp: hello

 1 #include <iostream>
 2 using namespace std;
 3 
 4 const float pi = 3.14f;
 5 float f;
 6 
 7 float f1(float r){
 8     f = r * r * pi;
 9     return f;
10 }
11 
12 float& f2(float r){
13     f = r * r * pi;
14     return f;
15 }
16 
17 int main(){
18     float f1(float=5);  // 声明 f1() 函数默认参数为5
19     float& f2(float=5); // 声明 f2() 函数默认参数为5
20     float a = f1();     // 78.5
21     float& b = f1();    // wrong
22     float c= f2();      // 78.5
23     float& d = f2();    // 78.5
24     d += 1.0f;          // 79.5
25     cout<<"a="<<a<<endl;  // 78.5
26     cout<<"b="<<b<<endl;  // 注释掉
27     cout<<"c="<<c<<endl;  // 78.5
28     cout<<"d="<<d<<endl;  // 79.5
29     cout<<"f="<<f<<endl;  // 79.5
30     return 0;
31 }

Non-const lvalue reference to type ‘float‘ cannot bind to a temporary of type ‘float‘