关键字之操作符（运算符）

C++新增操作符（运算符）：
new：分配内存空间
delete：释放内存空间
const_cast：
static_cast：
dynamic_cast：
reinterpret_cast：
this：
operator：
and, and_eq, bitand, bitor, compl, not, not_eq, or, or_eq, xor, xor_eq：各种运算符替代名

1.new和delete

int *ptr = new int;
*ptr = 10;

delete ptr;
ptr = NULL;
delete ptr;//if set ptr equalto NULL after delete ptr, delete ptr again will cause no problem, if not, that will cause double delete.

int *ptr2 = new int[10];
delete []ptr2;//[]-->表示批量删除，与new []保持一致
ptr2 = NULL;

2.const_cast、static_cast

const int i=10;
//int *p=&i; //error

//const-->const
//非const-->const
//const 不能-->非const 

const int* ptr=&i;//1
int *p2=(int*)&i;//2
*p2=20;
cout<<"i:"<<i<<endl;
cout<<"*p2:"<<*p2<<endl;

//const_cast
int *p3=const_cast<int*>(&i);//3,解除const限定,只能对指针和引用
*p3=30;
cout<<"i:"<<i<<endl;
cout<<"*p3:"<<*p3<<endl;

//static_cast
int num1=5, num2=2;
//double ret=double(num1)/num2;
double ret=static_cast<double>(num1)/num2;//强制类型转换
cout<<"ret:"<<ret<<endl;