[C++ Primer Plus] 第11章、使用类（一）程序清单——重载 P408

程序清单11.4~11.6（运算符重载——添加加法运算符）

//1.h
class Time {
private:
    int hours;
    int minutes;
public:
    Time();
    Time(int h, int m = );
    void AddMin(int m);
    void AddHr(int h);
    void Reset(int h=,int m=);
    Time operator+(const Time & t) const;//重载之前为：Time Sum(const Time & t) const;
    //只要把运算符（这里为“+”）放到operator后面，并将结果用做方法名即可
    void show() const;
};
 
//1.cpp
#include <iostream>
#include "1.h"
using namespace std;
 
Time::Time() {
    hours = minutes = ;
}
 
Time::Time(int h, int m) {
    hours = h;
    minutes = m;
}
void Time::AddMin(int m) {
    minutes += m;
    hours += minutes / ;
    minutes %= ;
 
}
void Time::AddHr(int h) {
    hours += h;
}
void Time::Reset(int h , int m ) {
    hours = h;
    minutes = m;
}
Time Time::operator+(const Time & t) const {
    Time sum;
    sum.minutes = minutes + t.minutes;
    sum.hours = hours + t.hours + sum.minutes / ;
    sum.minutes %= ;
    return sum;
}
void Time::show() const {
    cout <<" "<< hours << " hours, " << minutes << " minutes"<<endl;
}
 
//main.cpp
#include<iostream>
#include "1.h"
using namespace std;
 
void main() {
    Time plan,total;
    Time coding(, );
    Time fixing(, );
 
    cout << "planning time =";
    plan.show();
    cout << "coding time =";
    coding.show();
    cout << "fixing time =";
    fixing.show();
 
    int a = , b = ;
    cout << "a+b="<<a + b << endl;//int型加法
    total = coding + fixing;//Time型加法（即“+”号重载）
    cout << "coding + fixing =";
    total.show();
 
    Time morefixing(, );
    cout << "more fixing time =";
    morefixing.show();
 
    total = morefixing.operator+(total);
    cout << "morefixing.operator+(total) =";
    total.show();
 
    system("pause");
}

程序清单11.7~11.9

只贴出与上面代码不同的地方

//1.h
Time operator-(const Time & t) const;
Time operator*(double n) const;
 
//1.cpp
Time Time::operator-(const Time & t) const{
    Time diff;
    int tot1,tot2;
    tot1=t.minutes+*t.hours;
    tot2=minutes+*hours;
    diff.minutes=(tot2-tot1)%;
    diff.hours=(tot2-tot1)/;
    return diff;
}
Time Time::operator*(double n) const{
    Time result;
    long totalMinutes=hours*n*+minutes*n;
    result.hours=totalMinutes/;
    result.minutes=totalMinutes%;
    return result;
}
 
//main.cpp
#include<iostream>
#include "1.h"
using namespace std;
 
void main() {
    Time total,diff,adjust;
    Time weeding(, );
    Time waxing(, );
 
    cout << "weeding time =";
    weeding.show();
    cout << "waxing time =";
    waxing.show();
 
    total = weeding + waxing;
    cout << "weeding + waxing =";
    total.show();
 
    diff = weeding - waxing;
    cout << "weeding - waxing =";
    diff.show();
 
    adjust = total * 1.5;
    cout << "adjust work time =";
    adjust.show();
 
    system("pause");
}

程序清单11.10~11.12（友元）

只贴出与上面代码不同的地方

//1.h
friend Time operator*(double m,const Time &t) {    return t*m;    }//只有在类声明的原型中才能使用friend关键字
friend std::ostream & operator<<(std::ostream &os,const Time &t);
 
//1.cpp
std::ostream & operator<<(std::ostream &os,const Time &t){
    os << t.hours << " hours, " << t.minutes << " minutes";
    return os;
}
 
//main.cpp
#include<iostream>
#include "1.h"
using namespace std;
 
void main() {
    Time temp;
    Time aida(, );
    Time tosca(, );
 
    cout << "Aida and Tosca:\n";
    cout <<aida<<"; "<<tosca<<endl;
    temp=aida+tosca;
    cout << "Aida and Tosca:"<<temp<<endl;
    temp=aida*1.17;
    cout << "Aida * 1.17:"<<temp<<endl;
    cout << "10.0 * Tosca:"<<10.0*tosca<<endl;
 
    system("pause");
}

程序清单11.13~11.15（Vector实现矢量操作:模拟随机漫步）

 //1.h
 #ifndef VECTOR_H_
 #define VECTOR_H_
 #include<iostream>
 
 namespace VECTOR{
     class Vector    //类声明
     {
     public:
         enum Mode{RECT,POL};
     private:
         double x;
         double y;
         double mag;//长度
         double ang;//角度
         Mode mode;
         void set_mag();
         void set_ang();
         void set_x();
         void set_y();
     public:
         Vector();//默认构造函数
         Vector(double n1,double n2,Mode form=RECT);
         void reset(double n1,double n2,Mode form=RECT);
         ~Vector();//析构函数
         //以下四个函数在类声明中定义，因此自动成为内联函数；不改变对象数据，所以声明时使用const
         double xval() const {return x;}
         double yval() const {return y;}
         double magval() const {return mag;}
         double angval() const {return ang;}
         void polar_mode();
         void rect_mode();
         //重载
         Vector operator+(const Vector &b) const;
         Vector operator-(const Vector &b) const;
         Vector operator-() const;
         Vector operator*(double n) const;
         //友元
         friend Vector operator*(double n,const Vector &a);
         friend std::ostream &operator<<(std::ostream &os,const Vector &V);
     };
 }
 #endif
 
 //1.cpp
 #include <cmath>
 #include "1.h" //include <iostream>
 using namespace std;
 
 namespace VECTOR{
     const double Rad_to_deg=45.0/atan(1.0);
 
     void Vector::set_mag(){
         mag=sqrt(x*x+y*y);
     }
     void Vector::set_ang(){
         if(x==0.0&&y==0.0)
             ang=0.0;
         else
             ang=atan2(y,x);
     }
     void Vector::set_x(){
         x=mag*cos(ang);
     }
     void Vector::set_y(){
         y=mag*sin(ang);
     }
 
     Vector::Vector(){//默认构造函数
         x=y=mag=ang=0.0;
         mode=RECT;
     }
     Vector::Vector(double n1,double n2,Mode form){
         mode=form;
         if(form==RECT){
             x=n1;
             y=n2;
             set_mag();
             set_ang();
         }else if(form==POL){
             mag=n1;
             ang=n2/Rad_to_deg;
             set_x();
             set_y();
         }else{
             cout<<"Incorrect 3rd argument to Vector() -- vector set to 0"<<endl;
             x=y=mag=ang=0.0;
             mode=RECT;
         }
     }
 
     void Vector::reset(double n1,double n2,Mode form){
         mode=form;
         if(form==RECT){
             x=n1;
             y=n2;
             set_mag();
             set_ang();
         }else if(form==POL){
             mag=n1;
             ang=n2/Rad_to_deg;
             set_x();
             set_y();
         }else{
             cout<<"Incorrect 3rd argument to Vector() -- vector set to 0"<<endl;
             x=y=mag=ang=0.0;
             mode=RECT;
         }
     }
     Vector::~Vector(){}//析构函数
 
     void Vector::polar_mode(){
         mode=POL;
     }
     void Vector::rect_mode(){
         mode=RECT;
     }
 
     Vector Vector::operator+(const Vector &b) const{
         return Vector(x+b.x,y+b.y);
     }
     Vector Vector::operator-(const Vector &b) const{
         return Vector(x-b.x,y-b.y);
     }
     Vector Vector::operator-() const{
         return Vector(-x,-y);
     }
     Vector Vector::operator*(double n) const{
         return Vector(n*x,n*y);
     }
 
     Vector operator*(double n,const Vector &a){
         return a*n;
     }
     ostream &operator<<(ostream &os,const Vector &v){
         if(v.mode==Vector::RECT)
             os<<"(x,y)=("<<v.x<<", "<<v.y<<")";
         else if(v.mode==Vector::POL)
             os<<"(m,a)=("<<v.mag<<", "<<v.ang*Rad_to_deg<<")";
         else
             os<<"Vector object mode is invalid";
         return os;
     }
 }
 
 //main.cpp
 #include<iostream>
 #include<cstdlib>    //rand(),srand()
 #include<ctime>    //time()
 #include "1.h"
 using namespace std;
 using VECTOR::Vector;
 
 void main() {
     srand(time());    //随机数种子生成器
     double direction;
     Vector step;
     Vector result(0.0,0.0);
     unsigned long steps=;
     double target;
     double dstep;
     cout << "Enter target distance (q to quit):";
     while (cin>>target)
     {
         cout<<"Enter step length:";
         if(!(cin>>dstep))//输入错误就退出
             break;
         while (result.magval()<target)
         {
             direction=rand()%;
             step.reset(dstep,direction,Vector::POL);
             result=result+step;
             steps++;
         }
         cout<<"After "<<steps<<" steps,the subject has the following lacation:"<<endl;
         cout<<result<<endl;
         result.polar_mode();
         cout<<" or\n"<<result<<endl;
         cout<<"Average outward distance per step= "<<result.magval()/steps<<endl;
         steps=;
         result.reset(0.0,0.0);
         cout << "Enter target distance (q to quit):";
     }
     cout<<"Bye!\n";
     cin.clear();
     while (cin.get()!='\n')//直到换行才退出
         continue;
 
     system("pause");
 }

未完……