类型运算符

#include<iostream>
#include<memory>//new include to use unique_ptr
using namespace std;

class Date
{
private:
        int day, month, year;
        string dateInString;
        
public:
     Date(int inMonth,int inDay,int inYear)
        : month(inMonth), day(inDay), year(inYear){};
        
    void DisplayDate()
    {
        cout<< month << " / " << day << " / " << year <<endl;
    }        
};

int main()
{
    unique_ptr<int>smartIntPtr(new int);
    *smartIntPtr = 42;
   
    //Use smart pointer type like an int*
    cout<< "Integer value is: " << *smartIntPtr << endl;
   
    unique_ptr<Date>smartHoliday(new Date(12,25,2016));
    cout<<"The new instance of date contains: ";
   
    //use smartHoliday just as you would a Date*
    smartHoliday->DaisplayDate();
   
    return 0;
}
上面是编译器出的报错，代码明明和书上是一样的，出现报错一头雾水，有大神能给解惑一下吗？