operator引用貌似本对象@_@

    friend ostream& operator<<(ostream& os,const 类名 &类定义的){os<<类定义的.成员<<endl;return os;}
    friend istream& operator>>(istream &is,类名 &类定义的){is>>类定义的.成员;return is;}
    TT &operator++()
    TT operator++(int)//再定义一个类定义的
    TT &operator--()
    TT &operator--(int)//在定义一个类定义的

友出引运<<出引os常类引用

友入引运>>入引is类引用

后置无引用，多int多定义一个

class Time

{

private:

    int h,m,s;

public:

    Time():h(0),m(0),s(0) {}

    friend ostream& operator<<(ostream& os,const Time &a)

    {

        if(a.h>=0&&a.h<24&&a.m>=0&&a.m<60&&a.s>=0&&a.s<60)

            os<<setw(2)<<setfill('0')<<a.h<<":"<<setw(2)<<setfill('0')<<a.m<<":"<<setw(2)<<setfill('0')<<a.s;

        else

            os<<"error!!!";

        return os;

    }

    friend istream& operator>>(istream& is,Time& a)

    {

        is >> a.h>>a.m>>a.s;

        return is;

    }

    Time& operator--()

    {

        if(h>=0&&h<24&&m>=0&&m<60&&s>=0&&s<60)

        {

            --s;

            if(s<0)

            {

                s+=60;

                --m;

            }

            if(m<0)

            {

                m+=60;

                --h;

            }

            if(h<0)

                h+=24;

        }

        return *this;

    }

    Time operator--(int)

    {

        Time q=(*this);

        if(h>=0&&h<24&&m>=0&&m<60&&s>=0&&s<60)

        {

            --s;

            if(s<0)

            {

                s+=60;

                --m;

            }

            if(m<0)

            {

                m+=60;

                --h;

            }

            if(h<0)

                h+=24;

        }

        return q;

    }

    Time& operator++()

    {

        if(h>=0&&h<24&&m>=0&&m<60&&s>=0&&s<60)

        {

            ++s;

            if(s>=60)

            {

                s-=60;

                ++m;

            }

            if(m>=60)

            {

                m-=60;

                ++h;

            }

            if(h>=24)

                h-=24;

        }

        return *this;

    }

 

    Time operator++(int)

    {

        Time q=(*this);

        if(h>=0&&h<24&&m>=0&&m<60&&s>=0&&s<60)

        {

            s++;

            if(s>=60)

            {

                s-=60;

                m++;

            }

            if(m>=60)

            {

                m-=60;

                h++;

            }

            if(h>=24)

                h-=24;

        }

        return q;

    }

};