oop实验二

实验任务一

　　源代码

#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;           // 类T对象上限

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;
}

　　运行结果

　　问题一：不能正常运行。报错结果如下

 

原因：如果删去了viod func（），在task1.cpp文件中要调用fuc函数时会报错，因为没有找到fuc函数的声明。换句话来说就是友元函数不能代替函数的声明。

　　问题二：

普通构造函数，功能：用于创建类T对象时可以对对象的成员变量进行初始化，且如果有默认参数，则在没有传递参数时使用默认参数，在有传递参数时使用传递参数。调用时机：用于创建类T新对象。

复制构造函数，功能：用一个已经存在的T类对象t来创建一个新的T类对象，即新对象是副本，会复制已有对象的成员变量值。const则表示在复制过程中不会修改被复制的原有代码。调用时机：用于一个已有的T类对象创建一个新的T类对象时使用。

移动构造函数，功能：将一个T类对象的变量值移动到新对象中，类似于剪切粘贴。调用时机：当函数返回T类对象并用该返回值初始化新对象时。

析构函数，功能：在T类对象生命周期结束时，执行清理工作。调用时机：用于当T类对象的作用域结束时。

　　问题三：不能运行，结果如下。

错误原因是静态成员变量重复定义。

 

实验任务二

　　源代码

#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) = 5" << 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;
}

#include "Complex.h"
#include <cmath>
const std::string Complex::doc = "a simplified Complex class";

Complex::Complex(double r,double i) : real(r), imag(i) {}

Complex::Complex(const Complex&other) : real(other.real), imag(other.imag) {}

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

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

void Complex::add(const Complex& other) {
    real += other.real;
    imag += other.imag;
}

void output(const Complex& c) {
    std::cout << c.real;
    if (c.imag >= 0) {
        std::cout << " + " << c.imag << "i";
    } else {
        std::cout << " - " << -c.imag << "i";
    }
}

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

Complex add(const Complex&c1, const Complex&c2) {
    return Complex(c1.real + c2.real, c1.imag + c2.imag);
}

bool is_equal(const Complex&c1, const Complex&c2) {
    return c1.real==c2.real && c1.imag==c2.imag;
}

bool is_not_equal(const Complex&c1, const Complex&c2) {
    return !is_equal(c1,c2);
}

#include <string>
#include <iostream>

class Complex {
private:
    double real;
    double imag;

public:
    static const std::string doc;
    Complex(double r = 0.0, double i = 0.0);
    Complex(const Complex& other);
    
    double get_real() const;
    double get_imag() const;

    void add(const Complex& other);
    
    friend void output(const Complex& c);
    friend double abs(const Complex& c);
    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);
};

void output(const Complex& c);
double abs(const Complex& c);
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);

　　运行结果

　

　　问题一：标准库模板complex模板更简洁。函数和运算的内在有关联，和数学表达式具有类似一致性且不用额外记忆函数名。

　　问题二：2.1 是。output函数需要读取c.real,c.imag来格式化输出，abs函数需要同时使用实部和虚部，add和比较函数需要同时读取两个复数的实部和虚部。

　　　　2.2否。因为abs是普通函数。

　　　　2.3格式化输出/输入需要直接读取或设置多个私有成员，且不为了绕过封装而是为了扩展接口，因为友元函数有时可能会破坏封装性。

　　问题三：私有拷贝构造函数，在complex.h中private里面添加这行代码的声明。

 

实验任务三

　　源代码

#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();
}

#pragma once
#include <string>
enum class ControlType {Play,Pause,Next,Prev,Stop,Unknown};
class PlayerControl{
    private:
        static int total_cnt;
    public:
        PlayerControl();
        static int get_cnt;
        ControlType parse(const std::string& control_str);
        void execute(ControlType cmd) const
};

#include <iostream>
#include <algorithm>   

int PlayerControl::total_cnt = 0;

PlayerControl::PlayerControl() {}

ControlType PlayerControl::parse(const std::string& control_str) {
    std::string sent= control_str;
    std::transform(sent.begin(),sent.end(),sent.begin(), [](unsigned char c) {return std::tolower(c); });
    ControlType res;
    if (sent=="play")
        res=ControlType::Play;
    else if(sent=="pause")
        res=ControlType::Pause;
    else if(sent=="next")
        res=ControlType::Next;
    else if(sent=="prev")
        res = ControlType::Prev;
    else if(sent=="stop")
        res=ControlType::Stop;
    else
        res=ControlType::Unknown;

    total_cnt++;
    return res;
    
}

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;
}

　　运行结果

 

 

实验任务四

　　源代码

#include "Fraction.h"
#include <iostream>
using namespace std;

void test1();
void test2();

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();
    return 0;
}

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;
    
    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() {
    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;
}

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

using namespace std;

const 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。";

Fraction::Fraction(int up, int down) : up(up), down(down) {
    if (down == 0) {
        throw invalid_argument("分母不能为0");
    }
    simplify();
}

Fraction::Fraction(const Fraction& other) : up(other.up), down(other.down) {
    simplify();
}

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

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

Fraction Fraction::negative() const {
    return Fraction(-up, down);
}

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

void Fraction::simplify() {
    if (down < 0) {
        up = -up;
        down = -down;
    }
    
    int common = gcd(up, down);
    if (common != 0) {
        up /= common;
        down /= common;
    }
    
    if (up == 0) {
        down = 1;
    }
}

void output(const Fraction& f) {
    if (f.down == 1) {
        cout << f.up;
    } else {
        cout << f.up << "/" << f.down;
    }
}

Fraction add(const Fraction& f1, const Fraction& f2) {
    int new_up = f1.up * f2.down + f2.up * f1.down;
    int new_down = f1.down * f2.down;
    return Fraction(new_up, new_down);
}

Fraction sub(const Fraction& f1, const Fraction& f2) {
    int new_up = f1.up * f2.down - f2.up * f1.down;
    int new_down = f1.down * f2.down;
    return Fraction(new_up, new_down);
}

Fraction mul(const Fraction& f1, const Fraction& f2) {
    int new_up = f1.up * f2.up;
    int new_down = f1.down * f2.down;
    return Fraction(new_up, new_down);
}

Fraction div(const Fraction& f1, const Fraction& f2) {
    if (f2.up == 0) {
        cout << "分母不能为0";
        return Fraction(0, 1);
    }
    int new_up = f1.up * f2.down;
    int new_down = f1.down * f2.up;
    return Fraction(new_up, new_down);
}

　　问题：选择友元函数方案。

　　　　　理由：第一，这些函数都需要访问分子和分母，即类的私有成员，而友元函数可以直接访问，这样可以提高效率。第二，静态成员函数不依赖于对象实例的操作，但这个实例中依赖，故而不合适。第三，命名空间无法直接访问私有成员，这样效率会降低。虽然友元函数比其他两个更合适，但也有缺点，他破坏了封装性，因为可以访问类的私有成员，所以有可能导致类的内部状态被修改，不利于维护。