171014 C++学习笔记-4

例 4-1 时钟类的完整程序

// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include<iostream>  using namespace std;//Part One：定义类class Clock {public:    void setTime(int newH = 0, int newM = 0, int newS = 0);    void showTime();private:    int hour, minute, second;};//Part Two：成员函数的实现void Clock::setTime(int newH, int newM, int newS) {    hour = newH;    minute = newM;    second = newS;}inline void Clock::showTime() {    cout << hour << ":" << minute << ":" << second << endl;}//Part Three：主函数int main() {    Clock myClock;    cout << "First time set and output:" << endl;    myClock.setTime();    myClock.showTime();    cout << "Second time set and output:" << endl;    myClock.setTime(8, 30, 30);    myClock.showTime();    return 0;}

例 4-2 Point类的完整程序

// ConsoleApplication2.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include <iostream>using namespace std;class Point {public:    Point(int xx = 0, int yy = 0) { //内联函数        x = xx;        y = yy;    }    Point(Point &p);               // 复制构造函数    int getX() {        return x;    }    int getY() {        return y;        }private:    int x, y;};//成员函数的实现，复制构造函数Point::Point(Point &p) {    x = p.x;    y = p.y;    cout << "Calling the copy constructor" << endl;}// 形参为Poin类对象的函数void fun1(Point p) {    cout << p.getX() << endl;}// 返回值为Point类对象的函数Point fun2() {    Point a(1, 2);    return a;}int main(){    Point a(4, 5);              //第一个对象a    Point b = a;                //情况一，用a初始化b。第一次调用复制构造函数    cout << b.getX() << endl;       fun1(b);                    //情况二，对象b作为fun1的实参。第二次调用复制函数    b = fun2();                 //情况三，函数的返回值是类对象，函数返回时，调用复制构造函数    cout << b.getX() << endl;    return 0;}

例 4-3 游泳池改造预算，Circle类

// ConsoleApplication2.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include <iostream>using namespace std;const float PI = 3.141593;          //给出PI的值const float FENCE_PRICE = 35;       //栅栏的单价const float CONCRETE_PRICE = 20;    //过道水泥单价class Circle {                      //声明定义类Circle及其数据和方法public:                             //外部接口    Circle(float r);                //构造函数    float circumference();          //计算圆的周长    float area();                   //计算圆的面积private:                            //私有数据成员    float radius;                   //圆半径    };Circle::Circle(float r) {    radius = r;}// 等价于：Circle::Circle(float r):radius(r){} --->列表表达式，效率更高//计算圆的周长float Circle::circumference() {    return 2 * PI*radius;}//计算圆环的面积float Circle::area() {    return PI*radius*radius;}int main(){    float radius;    cout << "Enter the radius of the pool:";//提示用户输入半径    cin >> radius;    Circle pool(radius);                    //游泳池边界对象    Circle poolRim(radius + 3);             //栅栏对象    //计算栅栏造价并输出    float fenseCost = poolRim.circumference()*FENCE_PRICE;    cout << "Fencing Cost is $ " << fenseCost << endl;    //计算过道造价并输出    float concreCost = (poolRim.area() - pool.area())*CONCRETE_PRICE;    cout << "Concrete Cost is $ " << concreCost << endl;    return 0;}

例 4-4 类的组合，线段(Line)类

// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include<iostream>  #include<cmath>using namespace std;class Point {   //Point类的定义public:    //构造函数，隐式申明    Point(int xx = 0, int yy = 0) {        x = xx;        y = yy;    }    //复制构造函数    Point(Point &p);    //内联成员函数，隐式声明；    int getX() { return x; }    int getY() { return y; }private:    int x, y;};//复制构造函数的实现Point::Point(Point &p) {    x = p.x;    y = p.y;    cout << "Calling the copy constructor of Point" << endl;}//类的组合class Line { //Line类的定义public:      //外部接口    Line(Point xp1, Point xp2); //构造函数，形参为Point类    Line(Line &l);              //复制构造函数，内联成员函数    double getLen() { return len; }private:    Point p1, p2;               //Point类的对象p1,p2    double len;};//组合类的构造函数Line::Line(Point xp1, Point xp2) : p1(xp1), p2(xp2) //初始化列表，奖形参xp1,xp2赋予p1,p2{     cout << "Calling constructor of Line" << endl;    double x = static_cast<double>(p1.getX() - p2.getX());    double y = static_cast<double>(p1.getY() - p2.getY());    len = sqrt(x*x + y*y);                          //计算得到len，len仅能被Line类中的共有函数getLen()访问}//组合类的复制构造函数Line::Line(Line &l) :p1(l.p1), p2(l.p2)             //l为对象名{    cout << "Calling the copy constructor of Line" << endl;    len = l.len;}int main() {    Point myp1(1, 1), myp2(4, 5);               //建立Point类的对象    Line line(myp1, myp2);                      //建立Line类的对象    Line line2(line);                           //利用复制构造函数建立一个新对象    cout << "The length of the line is: ";    cout << line.getLen() << endl;    cout << "The length of the line2 is: ";    cout << line2.getLen() << endl;    return 0;}

例 4-7 用结构体表示学生的基本信息

有时程序中需要定义一些数据类型，它们并没有什么操作，定义它们的目的只是将一些不同类型的数据组合成一个整体，从而方便地保存数据，这样的类型不妨定义为结构体。

// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include<iostream>  //#include<iomanip> 流控制符：1.设置显示宽度 2.设置左右对齐 3.设置浮点数精度#include<string>using namespace std;struct Student {    int num;    string name;    char sex;    int age;};int main() {    Student stu = { 97001,"Lin Lin",'F',19 };    cout << "Num: " << stu.num << endl;    cout << "Name: " << stu.name << endl;    cout << "Sex: " << stu.sex << endl;    cout << "Age: " << stu.age << endl;    return 0;}

例 4-8 使用联合体保存成绩信息，并且输出

// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include<iostream>  #include<string>using namespace std;class ExamInfo {public:    //3种构造函数，分别用登记、是否通过和百分制来初始化    ExamInfo(string name, char grade)        :name(name), mode(GRADE), grade(grade) {}    ExamInfo(string name, bool pass)        :name(name), mode(PASS), pass(pass) {}    ExamInfo(string name, int percent)        :name(name), mode(PERCENTAGE), percent(percent) {}    void show();private:    string name;        //课程名称    enum {        GRADE,        PASS,        PERCENTAGE    }mode;              //采用何种计分方式,此处为何是这样的写法？？？    union {        char grade;     //等级制的成绩        bool pass;      //是否通过        int percent;    //百分制的成绩    };};void ExamInfo::show() //成员函数{    cout << name<<": ";    switch (mode) {    case GRADE: cout << grade;        break;    case PASS:        cout << (pass ? "PASS" : "FAIL");        break;    case PERCENTAGE:        cout << percent;        break;    }    cout << endl;}int main() {    ExamInfo course1("English", 'B');    ExamInfo course2("Calculus", true);    ExamInfo course3("C++Programming", 85);    course1.show();    course2.show();    course3.show();    return 0;}

例 4-9 个人银行账户管理程序

// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include<iostream>  #include<string>#include <cmath>using namespace std;class SavingsAccount {      //存储账户类private:    int id;                 //账号ID    double balance;         //余额    double rate;            //存款的年利率    int lastDate;           //上次变更余额的时间    double accumulation;        //余额按日累加之和    //记录一笔账，date为日期，amount为金额，desc为说明    void record(int date, double amount);    //获得指定日期为止的存款金额按日累加值    double accumulate(int date) const{        return accumulation + balance*(date - lastDate);    }public:    //构造函数    SavingsAccount(int date, int id, double rate);    int getId() { return id; }    double getBalance() { return balance; }    double getRate() { return rate; }    void deposit(int date, double amount);      //存入现金    void withdraw(int date, double amount);     //取出现金    //结算利息，每年1月1日调用一次该函数    void settle(int date);    //显示账户信息    void show();};//SavingsAccount 类相关成员函数的实现//-1 构造函数，初始化对象SavingsAccount::SavingsAccount(int date, int id, double rate)    :id(id), balance(0), rate(rate), lastDate(date), accumulation(0) {    cout << date << "\t#" << id << " is created" << endl;}//-2 void SavingsAccount::record(int date, double amount) {    accumulation = accumulate(date);    lastDate = date;    amount = floor(amount * 100 + 0.5) / 100;    balance += amount;    cout << date << "\t#" << id << "\t" << amount << "\t" << balance << endl;}//-3 void SavingsAccount::deposit(int date, double amount) {     record(date, amount); }//-4 void SavingsAccount::withdraw(int date, double amount) {    if (amount > getBalance())        cout << "Error: not enough money" << endl;    else        record(date, -amount);}//-5void SavingsAccount::settle(int date) {    double interest = accumulate(date)*rate / 365;    if (interest != 0)        record(date, interest);    accumulation = 0;}//-6void SavingsAccount::show() {    cout << "#" << id << "\tBalance: " << balance;}int main() {    //建立几个账号    SavingsAccount sa0(1, 21325302, 0.015);    SavingsAccount sa1(1, 58320212, 0.015);    //几笔账目    sa0.deposit(5, 5000);    sa1.deposit(25, 10000);    sa0.deposit(45, 5500);    sa1.withdraw(60, 4000);    //开户后第90天到了银行的计息日，结算所有账户的年息    sa0.settle(90);    sa1.settle(90);    //输出各个账户的信息    sa0.show(); cout << endl;    sa1.show(); cout << endl;    return 0;}