C++深度解析教程笔记6-const常量&引用数组

C++深度解析教程笔记6

• [第12课 - const常量&引用数组](#第12课 - const常量&引用数组)
• • 实验-const常量的判别
  • 实验-引用作为数组元素
  • 小结

本文学习自狄泰软件学院 唐佐林老师的 C++深度解析教程，图片全部来源于课程PPT，仅用于个人学习记录

第12课 - const常量&引用数组

实验-const常量的判别

#include <stdio.h>

int main()
{
    const int x = 1;//在符号表，是常量
    const int& rx = x;//rx是x的别名，对应为x分配的内存空间，rx是只读变量
    
    int& nrx = const_cast<int&>(rx);//去除只读属性，目标类型只能是指针或者引用
    
    nrx = 5;
    
    printf("x = %d\n", x);
    printf("rx = %d\n", rx);
    printf("nrx = %d\n", nrx);
    //三个变量地址是一样的
    printf("&x = %p\n", &x);
    printf("&rx = %p\n", &rx);
    printf("&nrx = %p\n", &nrx);
    //可变的
    volatile const int y = 2;//2没放符号表，放在内存里
    int* p = const_cast<int*>(&y);//目标类型指针
    
    *p = 6;//修改指针指向的值
    
    printf("y = %d\n", y);//y改变了，证明了volatile修饰的变量放到了内存里
    printf("p = %p\n", p);//y的地址
    
    const int z = y;//z是只读变量
    
    p = const_cast<int*>(&z);
    
    *p = 7;
    
    printf("z = %d\n", z);//变化了，说明了使用变量初始化的const常量是只读变量
    printf("p = %p\n", p);
    
    char c = 'c';
    char& rc = c;
    const int& trc = c;//const int &  <---  char  类型不同的引用会生成新的只读变量，跟c毫无关系
    
    rc = 'a';//更改引用 的值
    
    printf("c = %c\n", c);
    printf("rc = %c\n", rc);
    printf("trc = %c\n", trc);
        
    printf("&c = %p\n", &c);
    printf("&rc = %p\n", &rc);
    printf("&trc = %p\n", &trc);
    
    return 0;
}
/*
x = 1
rx = 5
nrx = 5
&x = 0060FEE4
&rx = 0060FEE4
&nrx = 0060FEE4
y = 6
p = 0060FEE0
z = 7
p = 0060FEDC
c = a
rc = a
trc = c
&c = 0060FEDB
&rc = 0060FEDB
&trc = 0060FEE8

*/

实验-引用作为数组元素

#include <stdio.h>

int a = 1;

struct SV
{
    int& x;
    int& y;
    int& z;
};

int main()
{
    int b = 2;
    int* pc = new int(3);
    SV sv = {a, b, *pc};

int &array[]={a,b}; error: declaration of 'array' as array of references
    //int& array[] = {a, b, *pc}; // &array[1] - &array[0] = ?  Expected ==> 4
// error: declaration of 'array' as array of references
    
    printf("&sv.x = %p\n", &sv.x);
    printf("&sv.y = %p\n", &sv.y);
    printf("&sv.z = %p\n", &sv.z);
//&sv.x = 0000000000403010
//&sv.y = 000000000061FE14
//&sv.z = 0000000000DA6E90
    
    delete pc;
    
    return 0;
}

小结