实验2 类和对象——基础编程1

一、实验目的

 加深对类，对象的理解，能够解释类的封装，类的接口

会使用C++语法规则正确定义，实现，测试类，会使用类创建对象，并基于对象编程

针对具体问题场景，练习运用面向对象思维进行设计，合理利用C++语言特性（访问权限控制，static,friend,const)，在数据共享和保护之间达到平衡

会用多文件方式组织代码

加深对C++内存资源管理技术的理解，能够解释构造函数，析构函数的用途，分析它们何时会被调用

二、实验准备

 类的抽象，设计

使用C++定义类，使用类创建对象的语法；构造/析构陈洁灵语法，用途及调用时机

类的共享与保护机制：访问权限控制，静态成员（static），友元（friend),const

多文件组织代码

 

三、实验内容

 

1. 实验任务1

代码：

 t.h

#pragma once
#include <string>

class T{
    public:
        T(int x = 0, int y = 0);
        T(const T &t);
        T(T &&t);
        ~T();
        void adjust ( int ratio );
        void display ( )const ;
    private:
        int m1,m2;
    public:
        static int get_cnt();
        
    public:
        static const std::string doc;
        static const int max_cnt;
    private:
        static int cnt ;
        
        friend void func();
        
};
    void func();

t.cpp

#include"t.h"
#include<iostream>
#include<string>

using std::cout;
using std::endl;
using std::string;

const std::string  T::doc{"a simple class sample"};
const int T :: max_cnt= 999;
int T::cnt = 0;
T ::T (int x,int y) :m1{x},m2{y}
{
    ++cnt;
    cout << "T constructor called.\n";
}

T ::T (const T &t) :m1{t.m1},m2{t.m2}
{
    ++cnt;
    cout << "T copy constructor called.\n";
}


T ::T(T &&t):m1{t.m1},m2{t.m2}
{
    ++cnt;
    cout << "T move constructor called.\n";
 } 
 
 T::~T(){
     --cnt;
     cout << "T destructor called.\n";
     
 } 
 void T::adjust(int ratio){
     m1*=ratio;
     m2*=ratio;
     
 }
 void T::display ()const
 {
     cout<<"("<<m1<<","<<"m2"<<")";
 }
 
 int T::get_cnt()
{
    return cnt;
}

void func()
{
    T t5(42);
    t5.m2=2049;
    cout << "t5=";t5.display();cout<<endl;
}

task1.cpp

#include"t.h"
#include<iostream>

using std::cout;
using std::endl;

void test ( );

int main()
{
    test();
    cout<<"\nmain:\n";
    cout<<"T objects'current count:"<<T::get_cnt()<<endl;
    
}

void test()
{
    cout<<"test class T:\n";
    cout<<"T info:"<<T::doc<<endl;
    cout<<"T objects'max count: "<<T::max_cnt<<endl;
    cout<<"T objects'current count: "<<T::get_cnt()<<endl<<endl;
    
    T t1;
    cout<<"t1 = ";t1.display();cout<<endl;
    
    T t2(3,4);
    cout <<"t2 = ";t2.display();cout<<endl;
    
    T t3(t2);
    t3.adjust(2);
    cout<<"t3 = ";t3.display();cout<<endl;
    
    T t4(std::move(t2));
    cout<<"t3 = ";t4.display();cout<<endl;
    
    cout<<"T objects'current count: "<<T::get_cnt()<<endl;
    func();
}

 

 

运行截图：

 

 

 

问题回答：

 

问题一：不可以去掉t.h中最后的void func();

friend void func()不可以作为一个完整的函数声明。没有给出函数的参数列表。故还是需要在在t.h最后加上void func();

问题二：构造函数是在对象被创建时利用特定的值构造对象，将对象初始化为一个特定的状态。

普通构造函数是创建一个对象假如有两个参数，就可以接受两个参数，如果没有参数就是使用自定义的默认值，可以是0或者其它。

复制构造函数是一个已经存在的对象创建新的对象的时候调用它，新对象与存在的对象状态相同。

移动构造函数它通过右值引用来实现资源的转移。

调用时机：调用构造函数结束后调用析构函数，析构的顺序与构造的顺序相反。

 

 问题三：

不能正确编译运行

 

2. 实验任务2

代码:

Complex.h

#pragma once
#include<string>

class Complex{
    //类属性 
    public:
        static const std::string doc;
        Complex(double a=0,double b=0);
        Complex(const Complex &c);
        
    
    //对象属性
    private:
        double real;
        double imag;
    //对象方法
    public:
         //接口：
           const double get_real();
           const double get_imag();
           Complex add(const Complex& c);
    //友元函数
    public:
        friend Complex add(const Complex &c1,const Complex &c2);
        friend bool is_equal(const Complex &c1,const Complex &c2);
        friend bool is_not_equal(const Complex &c1,const Complex &c2);
        friend void output(const Complex &c);
        friend double abs(const Complex &c);
         ~Complex();
};

 Complex add(const Complex &c1,const Complex &c2);
 bool is_equal(const Complex &c1,const Complex &c2);
 bool is_not_equal(const Complex &c1,const Complex &c2);
 void output(const Complex &c);
 double abs(const Complex &c);

Complex.cpp

#include"Complex.h"
#include<iostream>
#include<string>
#include<cmath>


using std::cout;
using std::endl;
using std::string;



//类属性 
const std::string Complex::doc={"a simplified complex class"};
Complex::Complex(double a,double b):real(a),imag{b} {};
Complex::Complex(const Complex &c){
    real=c.real;
    imag=c.imag;
}
//接口 
const double Complex::get_real(){
    return real;
    
}
const double Complex::get_imag(){
    return imag;
}
Complex Complex::add(const Complex& c) {
   return Complex(real + c.real, imag + c.imag);
}


Complex add(const Complex &c1,const Complex &c2){
    Complex c;
    c.real=c1.real+c2.real;
    c.imag=c1.imag+c2.imag;
    return c;
    
} 
 bool is_equal(const Complex &c1,const Complex &c2){
     if(c1.real==c2.real&&c1.imag==c2.imag)
         return 1;
     else
         return 0;
 }
 bool is_not_equal(const Complex &c1,const Complex &c2){
     if(c1.real!=c2.real||c1.imag!=c2.imag)
         return 1;
     else 
         return 0;
 }
 void output(const Complex &c){
     if(c.imag<0)
     cout<<c.real<<c.imag<<"i";
     else
     cout<<c.real<<"+"<<c.imag<<"i";
 }
 double abs(const Complex &c){
     return sqrt(c.real*c.real+c.imag*c.imag);
 }
Complex::~Complex()=default;

 

 

运行截图：

 

 

 

 

 

 

 

3. 实验任务3

代码：

 

#include <iostream>
#include <complex>

using std::cout;
using std::endl;
using std::boolalpha;
using std::complex;

void test() {
    cout << "标准库模板类comple测试: " << endl;
    complex<double> c1;
    complex<double> c2(3, -4);
    const complex<double> c3(3.5);
    complex<double> c4(c3);

    cout << "c1 = " << c1 << endl;
    cout << "c2 = " << c2 << endl;
    cout << "c3 = " << c3 << endl;
    cout << "c4 = " << c4 << endl;
    cout << "c4.real = " << c4.real() << ", c4.imag = " << c4.imag() << endl;
    cout << endl;

    cout << "复数运算测试: " << endl;
    cout << "abs(c2) = " << abs(c2) << endl;
    c1 += c2;
    cout << "c1 += c2, c1 = " << c1 << endl;
    cout << boolalpha;
    cout << "c1 == c2 : " << (c1 == c2) << endl;
    cout << "c1 != c3 : " << (c1 != c3) << endl;
    c4 = c2 + c3;
    cout << "c4 = c2 + c3, c4 = " << c4 << endl;
}

int main() {
    test();
}

 

 

运行截图：

 

 

 

 问题回答：

 

 

 

4. 实验任务4

代码：

Fraction.h

#pragma once
#include<string>

class Fraction{
    public:
        static const std::string doc;
        Fraction(int up=1,int down=1);
        Fraction(const Fraction &c);
        
    int get_up()const;
    int get_down() const ;
    Fraction negative() const;
    static int gcd(int a,int b);
    Fraction simplify()const;
        
    public:    
    //友元函数
        friend void output(const Fraction &c);
        friend Fraction add(const Fraction &c1,const Fraction &c2);
        friend Fraction sub(const Fraction &c1,const Fraction &c2);
        friend Fraction mul(const Fraction &c1,const Fraction &c2);
        friend Fraction div(const Fraction &c1,const Fraction &c2);
        ~Fraction();
    private:
        int up;
        int down;
        
         
};

Fraction.cpp

#include"Fraction.h"
#include<iostream>
#include<string>
#include<cmath>
#include <iomanip> 

using std::cout;
using std::endl;
using std::string;




const std::string Fraction::doc={"Fraction类v 0.01版.\n目前仅支持分数对象的构造、输出、加/减/乘/除运算.\n"};
Fraction::Fraction(int a,int b):up(a),down{b} {}


Fraction::Fraction(const Fraction &c):up(c.up),down(c.down){
}

//简化分数 
Fraction Fraction::simplify()const{
    
int divisor=gcd(up,down);

 return Fraction(up/divisor,down/divisor);}

 
int Fraction::get_up()const{
    Fraction c1=this->simplify();
    

    return c1.up;
}
    

 int Fraction::get_down()const{
     Fraction c2=this->simplify();
    return c2.down;
    
}
Fraction Fraction::negative()const {
    
    return Fraction(-up,down);
}

int Fraction::gcd(int a,int b){

    while(b!=0){
        int temp=b;
        b=a%b;
        a=temp;
    }return a;
    
    
}


void output(const Fraction &c){
    
        
        if(c.down==0){cout<<"分母不能为0"; return;
        }
        if(c.up==0){cout<<0;return;}
    
            Fraction c1=c.simplify();
            if(c1.down==1){cout<<c.up;
                
            }
            else{cout<<c1.get_up()<<"/"<<c1.get_down() ;
            }

    }

    

    


Fraction add(const Fraction &c1,const Fraction &c2){
    
    Fraction c3;
    c3.up=c1.up*c2.down+c2.up*c1.down;
    c3.down=c1.down*c2.down;
    
     return c3.simplify();

    
}

Fraction sub(const Fraction &c1,const Fraction &c2){
    Fraction c3;
    c3.up=c1.up*c2.down-c2.up*c1.down;
    c3.down=c1.down*c2.down;
    
    return c3.simplify();
}
    
Fraction mul(const Fraction &c1,const Fraction &c2){
    Fraction c3;
    c3.up=c1.up*c2.up;
    c3.down=c1.down*c2.down;
    
    return c3.simplify();
}


Fraction div(const Fraction &c1,const Fraction &c2){
    Fraction c3;
    c3.up=c1.up*c2.down;
    c3.down=c1.down*c2.up;
    
    return c3.simplify();
}

Fraction::~Fraction()=default;

 

 Fraction_test.cpp

#include "Fraction.h"
#include <iostream>

using std::cout;
using std::endl;


void test1() {
    cout << "Fraction类测试: " << endl;
    cout << Fraction::doc << endl << endl;

    Fraction f1(5);
    Fraction f2(3, -4), f3(-18, 12);
    Fraction f4(f3);
    cout << "f1 = "; output(f1); cout << endl;
    cout << "f2 = "; output(f2); cout << endl;
    cout << "f3 = "; output(f3); cout << endl;
    cout << "f4 = "; output(f4); cout << endl;

    Fraction f5(f4.negative());
    cout << "f5 = "; output(f5); cout << endl;
    cout << "f5.get_up() = " << f5.get_up() << ", f5.get_down() = " << f5.get_down() << endl;

    cout << "f1 + f2 = "; output(add(f1, f2)); cout << endl;
    cout << "f1 - f2 = "; output(sub(f1, f2)); cout << endl;
    cout << "f1 * f2 = "; output(mul(f1, f2)); cout << endl;
    cout << "f1 / f2 = "; output(div(f1, f2)); cout << endl;
    cout << "f4 + f5 = "; output(add(f4, f5)); cout << endl;
}

void test2() {
    Fraction f6(42, 55), f7(0, 3);
    cout << "f6 = "; output(f6); cout << endl;
    cout << "f7 = "; output(f7); cout << endl;
    cout << "f6 / f7 = "; output(div(f6, f7)); cout << endl;
}

int main() {
    cout << "测试1: Fraction类基础功能测试\n";
    test1();

    cout << "\n测试2: 分母为0测试: \n";
    test2();
}

 

 

运行截图：

 

 

 

 

 

 

 

5. 实验任务5

代码：

Bank.h

#ifndef ACCOUNT_H
#define ACCOUNT_H

class SavingsAccount{
    private://用户的Id ，平均数，利率，上次存款时间，计算，总和这些数是私有的。 
        int id;
        double balance;
        double rate;
        int lastDate;
        double accumulation;
        static double total;
        void record(int data,double amount);//一个成员函数：用于输出 
        double accumulate(int date)const{return accumulation+balance*(date-lastDate);}
    public:
    SavingsAccount(int date,int id,double rate);
    int getId()const{return id;    }
    double getBalance ()const {return balance;}
    double getRate()const{return rate;}
    static double getTotal(){return total;
    }
    void deposit(int date,double amount);//存 
    void withdraw(int date,double amount);//取 
    void settle(int date);//结算 
    void show()const;
};
#endif 

Bank.cpp

#include <iostream>
#include "bank.h"
#include <cmath>

using namespace std;
 
double SavingsAccount::total = 0;

SavingsAccount::SavingsAccount(int date, int id, double rate): id(id), balance(0), rate(rate), lastDate(date), accumulation(0) {
     std::cout << date << "\t#" << id << " is created" << std::endl;
 }
void SavingsAccount::record(int date, double amount) {
accumulation = accumulate(date);
lastDate = date;
amount = floor(amount * 100 + 0.5) / 100;     //保留小数点后两位
balance += amount;
total += amount;
std::cout << date << "\t#" << id << "\t" << amount << "\t"<< balance << std::endl;
}
 void SavingsAccount::deposit(int date, double amount) {
record(date, amount);
}
void SavingsAccount::withdraw(int date, double amount) {
if (amount > getBalance()) {
std::cout << "Error: not enough money" << std::endl;
}
else {
record(date, -amount);
}
}
void SavingsAccount::settle(int date) {
double interest = accumulate(date) * rate / 365;        //计算年息
if (interest != 0) 
record(date, interest);
accumulation = 0;
}
void SavingsAccount::show() const {
std::cout << "#" << id << "\tBalance: " << balance;
}

Bank_test.cpp

#include "bank.h"
#include <iostream>
using namespace std;
int main() {

SavingsAccount sa0(1, 21325302, 0.015);
SavingsAccount sal(1, 58320212, 0.015);

sa0.deposit(5, 5000);
sal.deposit(25, 10000);
sa0.deposit(45, 5500);
sal.withdraw(60, 4000);

sa0.settle(90);
sal.settle(90);

sa0.show();
cout << endl;
sal.show();
cout << endl;
 cout << "Total: " << SavingsAccount::getTotal() << endl;
 return 0;
}

 

 

 

运行截图：

 

 

 个人银行账户管理系统使用了SavingsAccout()类封装了相关类的属性以及方法。也有不到位的地方，比如输入日期，钱数，取款数这些数据，要设置确保数据的输入是合理的，部分不能为负数。