C++语言基础 例程 重载单目运算符

贺老师的教学链接  本课讲解

示例1：分数类对象的相反数

class CFraction
{
private:
    int nume;  // 分子
    int deno;  // 分母
public:
    CFraction(int nu=0,int de=1):nume(nu),deno(de) {}
    CFraction operator-(const CFraction &c);  //两个分数相减，结果要化简
    CFraction operator-();  //取反一目运算
};

// 分数相减
CFraction CFraction:: operator-(const CFraction &c)
{
    CFraction t;
    t.nume=nume*c.deno-c.nume*deno;
    t.deno=deno*c.deno;
    t.simplify();
    return t;
}

// 分数取负号
CFraction CFraction:: operator-()
{
    CFraction x;
    x.nume=-nume;
    x.deno=deno;
    return x;
}

案例：Time类的++

#include <iostream>
using namespace std;
class Time
{
public:
    Time( )
    {
        minute=0;
        sec=0;
    }
    Time(int m,int s):minute(m),sec(s) { }
    Time operator++( );
    Time operator++(int);
    void display( )
    {
        cout<<minute<<":"<<sec<<endl;
    }
private:
    int minute;
    int sec;
};
Time Time::operator++( )
{
    if(++sec>=60)
    {
        sec-=60;
        ++minute;
    }
    return *this;
}

Time Time::operator++(int)
{
    Time temp(*this);
    sec++;
    if(sec>=60)
    {
        sec-=60;
        ++minute;
    }
    return temp;
}

int main( )
{
    Time time1(34,59),time2;
    cout<<" time1 : ";
    time1.display( );
    ++time1;
    cout<<"++time1: ";
    time1.display( );
    time2=time1++;          //将自加前的对象的值赋给time2
    cout<<"time1++: ";
    time1.display( );
    cout<<" time2 :";
    time2.display( );          //输出time2对象的值
    return 0;
}