实验二

task1

（1）

#pragma once

#include<string>

//类T:声明
class T{
//对象属性、方法
    public:
     T(int x=0,int y=0);// 普通构造函数
     T(const T &t);// 复制构造函数
     T(T &&t); // 移动构造函数
     ~T();// 析构函数
     
     void adjust(int ratio);// 按系数成倍调整数据
     void display() const;// 以(m1, m2)形式显示T类对象信息
     
private:
    int m1,m2;
// 类属性、方法
public:
    static int get_cnt();// 显示当前T类对象总数
    
public:
    static const std::string doc;    // 类T的描述信息
    static const int max_cnt;
    
private:
    static int cnt;// 当前T类对象数目
    
    // 类T友元函数声明
    friend void func();
}; 

 // 普通函数声明
 void func();

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

//类T实现

// static成员数据类外初始化
const std::string T::doc{"a simple class sample"};
const int T::max_cnt=999;
int T::cnt=0;

//类方法
int T::get_cnt(){
    return cnt;
}

// 对象方法
T::T(int x,int y):m1{x},m2{y}{
    ++cnt;
    std::cout<<"T constructor called.\n";
} 

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

T::T(T &&t):m1{t.m1},m2{t.m2}{
    ++cnt;
    std::cout<<"T move constructor called.\n";
}
T::~T(){
    --cnt;
    std::cout<<"T destructor called.\n";    
}

void T::adjust(int ratio){
    m1*=ratio;
    m2*=ratio;
}
void T::display() const{
    std::cout<<"("<<m1<<","<<m2<<")";
}

// 普通函数实现
void func(){
    T t5(42);
    t5.m2=2049;
    std::cout<<"t5=";
    t5.display();
    std::cout<<'\n';
}

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

void test_T();

int main(){
    std::cout<<"test Class T:\n";
    test_T();
    
    std::cout<<"\ntest friend func:\n";
    func();
}

void test_T(){
    using std::cout;
    using std::endl;
    
    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<<"t4=";t4.display();cout<<endl;
    
    cout<<"test:T objects'current count:"<<T::get_cnt()<<endl;
}

(2)运行结果截图

 （3）问题一：

原因：func（）函数未声明。

 问题二：T(int x=0,int y=0)是普通构造函数且带默认参数，它的功能是如果调用时没有参数，则用默认值。调用机制：当以非拷贝和非移动的方式创建对象时。

　　　　T(const T &t)是复制构造函数，功能是使用一个已存在的对象来初始化同类的一个新对象。调用时机：①当用类的一个对象去初始化该类的另一个对象时。②如果函数的形参是类的对象，调用函数时，进行形参和实参结合时。③如果函数的返回值是类的对象，函数执行完成返回调用者时。

　　　　T(T &&t);是移动构造函数。功能是使用一个右值引用来初始化新对象，将资源从源对象移动到新对象，源对象不再拥有资源。调用时机：从函数返回一个临时对象时。

　　　　~T();是析构函数，功能是用来完成对象被删除前的一些清理工作。调用世纪：在对象的生存期即将结束的时刻被自动调用的。

问题三：可以正确编译。

task2

（1）

#pragma once
#include<string>

class Complex{
    public:        
        static const std::string doc;
        
        Complex(double xx=0,double yy=0);
        Complex(const Complex &t);
        Complex(Complex &&t);
        ~Complex()=default;
         
         Complex &operator=(const Complex &m1);
         void add(const Complex &m1);                                        
        double get_real() const;
        double get_imag() const;
    private:
        double x,y;
};

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

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

const std::string Complex::doc="a simplified complex class";

Complex::Complex(double xx,double yy):x(xx),y(yy){}

Complex::Complex(const Complex &t):x(t.x),y(t.y){}

Complex::Complex(Complex &&t):x(t.x),y(t.y){}

Complex& Complex::operator=(const Complex &m1){
    if(this!=&m1)
    {
        x=m1.x;
        y=m1.y;
    }
    return *this;
}

double Complex::get_real() const{return x;}

double Complex::get_imag() const{return y;}

void Complex::add(const Complex &m1){
    x+=m1.x;
    y+=m1.y;
}

void output(const Complex &c){
    double x=c.get_real();
    double y=c.get_imag();
    
    std::cout<<x;
    if(y>=0){
        std::cout<<"+"<<y<<"i";
    }
    else{
        std::cout<<"-"<<-y<<"i";
    }
}

double abs(const Complex &c){
    return std::sqrt(c.get_real()*c.get_real()+c.get_imag()*c.get_imag());
}

Complex add(const Complex &c1,const Complex &c2){
    return  Complex(c1.get_real()+c2.get_real(),c1.get_imag()+c2.get_imag());
}
bool is_equal(const Complex &a,const Complex &b){
    return a.get_real()==b.get_real()&&a.get_imag()==b.get_imag();
}
bool is_not_equal(const Complex &a,const Complex &b){
    return !is_equal(a,b);
}

#include"Complex.h"
#include <iostream>
#include <iomanip>
#include <complex>
 void test_Complex();
 void test_std_complex();
 int main() {
 std::cout << "*******测试1: 自定义类Complex*******\n";
 test_Complex();
 std::cout << "\n*******测试2: 标准库模板类complex*******\n";
 test_std_complex();
 }
 void test_Complex() {
 using std::cout;
 using std::endl;
 using std::boolalpha;
 cout << "类成员测试: " << endl;
 cout << Complex::doc << endl << endl;
 cout << "Complex对象测试: " << endl;
 Complex c1;
 Complex c2(3, -4);
 Complex c3(c2);
 Complex c4 = c2;
 const Complex c5(3.5);
  cout << "c1 = "; output(c1); cout << endl;
 cout << "c2 = "; output(c2); cout << endl;
 cout << "c3 = "; output(c3); cout << endl;
 cout << "c4 = "; output(c4); cout << endl;
 cout << "c5.real = " << c5.get_real() 
<< ", c5.imag = " << c5.get_imag() << endl << endl;
 cout << "复数运算测试: " << endl;
 cout << "abs(c2) = " << abs(c2) << endl;
 c1.add(c2);
 cout << "c1 += c2, c1 = "; output(c1); cout << endl;
 cout << boolalpha;
 cout << "c1 == c2 : " << is_equal(c1, c2) << endl;
 cout << "c1 != c2 : " << is_not_equal(c1, c2) << endl;
 c4 = add(c2, c3);
 cout << "c4 = c2 + c3, c4 = "; output(c4); cout << endl;
 }
 void test_std_complex() {
 using std::cout;
 using std::endl;
 using std::boolalpha;
 cout << "std::complex<double>对象测试: " << endl;
 std::complex<double> c1;
 std::complex<double> c2(3, -4);
 std::complex<double> c3(c2);
 std::complex<double> c4 = c2;
 const std::complex<double> c5(3.5);
 cout << "c1 = " << c1 << endl;
 cout << "c2 = " << c2 << endl;
 cout << "c3 = " << c3 << endl;
 cout << "c4 = " << c4 << endl;
 cout << "c5.real = " << c5.real() 
<< ", c5.imag = " << c5.imag() << endl << 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 != c2 : " << (c1 != c2) << endl;
 c4 = c2 + c3;
 cout << "c4 = c2 + c3, c4 = " << c4 << endl;
 }

(2)运行测试截图

 （3）回答问题

问题1：标准库模板类complex的使用形式更简洁；函数和运算内在有关联。

问题2：2-1.否。因为output/abs/add等函数都可以通过公有接口get_real()和get_imag()来访问数据。

　　　　2-2.否。std::abs(std::complex)是一个独立的模板函数，不是友元函数。

　　　　2-3.当需要访问类的私有成员且无法通过公有接口实现时。

问题3：将拷贝构造函数声明为 explicit Complex(const  Complex &t);

 

task3

（1）

#pragma once
#include <string>
 
enum class ControlType {Play, Pause, Next, Prev, Stop, Unknown};
 
class PlayerControl {
public:
    PlayerControl();
 
    static int get_cnt();
    ControlType parse(const std::string& control_str);   // 实现std::string --> ControlType转换
    void execute(ControlType cmd) const;   // 执行控制操作（以打印输出模拟）       
private:
    static int total_cnt;  
};

 #include "PlayerControl.h"
 #include <iostream>
 #include <algorithm>   
 
int PlayerControl::total_cnt = 0;
 PlayerControl::PlayerControl() {}
 // 待补足
// 1. 将输入字符串转为小写，实现大小写不敏感
// 2. 匹配"play"/"pause"/"next"/"prev"/"stop"并返回对应枚举
// 3. 未匹配的字符串返回ControlType::Unknown
 // 4. 每次成功调用parse时递增total_cnt
 ControlType PlayerControl::parse(const std::string& control_str) {
    std::string lower_str;
    for(auto c:control_str)
        lower_str+=std::tolower(c);
    
    ControlType result=ControlType::Unknown;
    
    if(lower_str=="play")
    {
        result=ControlType::Play;
    }
    else if(lower_str=="pause")
    {
        result=ControlType::Pause;
    }
    else if(lower_str=="next")
    {
        result=ControlType::Next;
    }
    else if(lower_str=="prev")
    {
        result=ControlType::Prev;
    }
    else if(lower_str=="stop")
    {
        result=ControlType::Stop;
    }
    
    if(result!=ControlType::Unknown){
        total_cnt++;
    }
    return result;
 }
 void PlayerControl::execute(ControlType cmd) const {
    switch (cmd) {
    case ControlType::Play:  std::cout << "[play] Playing music...\n"; break;
    case ControlType::Pause: std::cout << "[Pause] Music paused\n";    break;
    case ControlType::Next:  std::cout << "[Next] Skipping to next track\n"; break;
    case ControlType::Prev:  std::cout << "[Prev] Back to previous track\n"; break;
    case ControlType::Stop:  std::cout << "[Stop] Music stopped\n"; break;
    default:                 std::cout << "[Error] unknown control\n"; break;
    }
 }
 int PlayerControl::get_cnt() {
    return total_cnt;
 }

#include "PlayerControl.h"
#include <iostream>
void test()
{
    PlayerControl controller;
    std::string control_str;
    std::cout << "Enter Control: (play/pause/next/prev/stop/quit):\n";
    while(std::cin >> control_str) {
        if(control_str == "quit")
            break;
        
        ControlType cmd = controller.parse(control_str);
        controller.execute(cmd);
        std::cout << "Current Player control: " << PlayerControl::get_cnt() << "\n\n";
    }
}
int main() {
    test();
 }

(2)运行测试截图

 task4

（1）

#pragma once
#include<string>

class Fraction{
    public:
        static const std::string doc;
    
    private:
        int up_;
        int down_;
        
        void simplify();
        static int gcd(int a,int b);
    
    public:    
        Fraction(int up=0,int down=1);
        Fraction(const Fraction &t);
        Fraction(Fraction &&t)=default;
        ~Fraction()=default;
        
        Fraction& operator=(const Fraction &c);
        int get_up()const;
        int get_down()const;
        Fraction negative()const;    
    
};

void output(const Fraction &c);
Fraction add(const Fraction &c1,const Fraction &c2);
Fraction sub(const Fraction &c1,const Fraction &c2);
Fraction mul(const Fraction &c1,const Fraction &c2);
Fraction div(const Fraction &c1,const Fraction &c2);

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

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。";

int Fraction::gcd(int a, int b) {
    a = std::abs(a);
    b = std::abs(b);
    while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }
    return a;
}


void Fraction::simplify() {
    if (down_ == 0) {
        return; 
    }
    
    
    if (down_ < 0) {
        up_ = -up_;
        down_ = -down_;
    }
    
  
    int common_divisor = gcd(up_, down_);
    if (common_divisor != 0) {
        up_ /= common_divisor;
        down_ /= common_divisor;
    }
    
    
    if (up_ == 0) {
        down_ = 1;
    }
}


Fraction::Fraction(int up, int down) : up_(up), down_(down) {
    if (down_ == 0) {
        
        return;
    }
    simplify();
}

Fraction::Fraction(const Fraction &t) : up_(t.up_), down_(t.down_) {}


Fraction& Fraction::operator=(const Fraction &c) {
    if (this != &c) {
        up_ = c.up_;
        down_ =c.down_;
    }
    return *this;
}


int Fraction::get_up() const {
    return up_;
}

int Fraction::get_down() const {
    return down_;
}

Fraction Fraction::negative() const {
    return Fraction(-up_, down_);
}


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

Fraction add(const Fraction &c1, const Fraction &c2) {
    int new_up = c1.get_up() * c2.get_down() + c2.get_up() * c1.get_down();
    int new_down = c1.get_down() * c2.get_down();
    return Fraction(new_up, new_down);
}

Fraction sub(const Fraction &c1, const Fraction &c2) {
    int new_up = c1.get_up() * c2.get_down() - c2.get_up() * c1.get_down();
    int new_down = c1.get_down() * c2.get_down();
    return Fraction(new_up, new_down);
}

Fraction mul(const Fraction &c1, const Fraction &c2) {
    int new_up = c1.get_up() * c2.get_up();
    int new_down = c1.get_down() * c2.get_down();
    return Fraction(new_up, new_down);
}

Fraction div(const Fraction &c1, const Fraction &c2) {
    if (c2.get_up() == 0) {
        return Fraction(1, 0);
    }
    int new_up = c1.get_up() * c2.get_down();
    int new_down = c1.get_down() * c2.get_up();
    return Fraction(new_up, new_down);
}

#include "Fraction.h"
 #include <iostream>
 void test1();
 void test2();
 int main() {
 std::cout << "测试1: Fraction类基础功能测试\n";
 test1();
 std::cout << "\n测试2: 分母为0测试: \n";
 test2();
 }
 void test1() {
 using std::cout;
 using std::endl;   
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;

 const 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() {
 using std::cout;
 using std::endl;
 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;
 }

（2）运行测试截图

 （3）回答问题：

问题：自由函数。原因：具有更好的封装性和清晰的接口分离。友元破坏了封装性。静态成员函数不适合这种纯计算。