c++ const_cast操作符、指针常量和常量指针的解释

#include <iostream>
using namespace std;
int main()
{
//const_cast的用法
{
int a = 2;
const int b = 3;
//int *f = &b;
int *c = const_cast<int*>(&b);//建立了b的临时变量
*c = 6;//不能改变b的值
int &d = a;
d = 23;
cout << &b << endl << c <<endl;
cout << b << " " << *c << "*****" << a << " " << d <<endl;
cout << &b << endl << c <<endl;

int p = 20;

const int *pp = &p;

int *ppp = const_cast<int *>(pp);

*ppp = 30;

//*pp = 40;错误，但是可以通过PPP来改变pp的值
cout << pp << endl << ppp << endl << &p;
cout << *pp << p <<endl; //3030
}
//指针常量和常量指针
{
int a = 2;
int b = 3;
const int * c = &a;//常量指针，可改变指向地址的指针
c = &b;//正确
//*c = 5;不正确
int * const d = &a;//指针常量，可改变指向变量值的指针
*d = 5;//正确
//d = &b;//不正确
}
}