这个程序错在哪？不解

[MichaelBomb]

#include <iostream>
//#include <string.h> //C header
#include <string>
//#include <stdio.h>
using namespace std;
class dayType
{
public:
enum dayTypeWeek{Mon,Tue,Wed,Thu,Fri,Sat,Sun,unKnown};
dayType();
~dayType();

void SetWeek(dayTypeWeek d);
void Print();
dayTypeWeek GetWeek(unsigned int iAdd = 0);
dayTypeWeek GetFront();
dayTypeWeek GetAfter();
private:
dayTypeWeek dayWeek;
};

// daytype.cpp文件
//#include "daytype.h"

dayType::dayType()
{
SetWeek(unKnown);
} ;
dayType::~dayType()
{
}
void dayType::SetWeek(dayTypeWeek d)
{
dayWeek = d;
}

void dayType::Print()
{
string out;
switch (dayWeek)
{
case unKnown:
out = "unKnown";
break;
case Mon:
out = "Mon";
break;
case Tue:
out = "Tue";
break;
case Wed:
out = "Wed";
break;
case Thu:
out = "Thu";
break;
case Fri:
out = "Fri";
break;
case Sat:
out = "Sat";
break;
case Sun:
out = "Sun";
break;
} //end switch
cout <<out<<endl;
}

dayTypeWeek dayType::GetWeek(unsigned int iAdd = 0)
{
return (iAdd + dayWeek) % 7;
}
dayTypeWeek dayType::GetFront()
{
return (dayWeek - 1) % 7;
}
dayTypeWeek dayType::GetAfter()
{
return GetWeek(1);
}

void main()
{
dayType dT;
dt.SetWeek(Mon);
dt.Print();
dt.GetWeek(2);
dt.Print();
}

[toxise]

dayweek应该是一个枚举类型吧？

怎么就和其他类型 相加减了？