实验2

实验任务1：

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;
    static int get_cnt();
public:
    static const std::string doc;
    static const int max_cnt;
    
private:
    int m1, m2;
    static int cnt;
    friend void func();
};
void func();

T.cpp

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

using namespace std;
const string T::doc("a simple class sample");
const int T::max_cnt = 999;
int T::cnt = 0;
int T::get_cnt() {
    return cnt;
}
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 << ")";
}
void func() {
    T t5(42);
    t5.m2 = 2049;
    cout << "t5="; t5.display(); cout << "\n";
}

task1.cpp

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

using namespace std;

void test_T() {
    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;
    cout << "\nTesting friend function:\n";
    func();
}

int main() {
    test_T();
    return 0;
}

实验结果：

 问题1：

不能被编译，

友元函数不被申明，只有定义就无法找到位置，程序自然无法运行

问题2：

T（int x=0,int y=0）用于输出内容.用在申明对象的时候

T(const T &t) 此函数为

构造函数，用于复制基本函数所输出的内容。。用以有对象来初始化新对象

T（T&&t）移动构造函数 移动从右值移动到一个新对象

~T（）  用于释放对象占用资源 用在离开作用域的时候

问题3：

yes

实验任务2：

 Complex.h:

#pragma once
#include <string>

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);

Complex.cpp

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

using namespace std;
const 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) {
    cout << c.real;
    if (c.imag >= 0) {
        cout << " + " << c.imag << "i";
    } else {
        cout << " - " << -c.imag << "i";
    }
}

double abs(const Complex& c) {
    return 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);
}

task.cpp

#include <iostream>
#include <iomanip>
#include <complex>
#include "Complex.h"

using namespace std;

void test_Complex();
void test_std_complex();

int main() {
    cout << "******测试1：自定义类Complex******" << endl;
    test_Complex();
    cout << "\n******测试2：标准库模板类Complex******" << endl;
    test_std_complex();
    return 0;
}

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;
}

运行结果：

问题1：

标准库模板complex更简洁；有关，标准库通过运算符重载写出运算代码，给更加直观。

问题2：

2.1：

需要；output需要访问real和imag来进行输出

abs需要访问real和imag来计算模长

add需要进行加法运算

is_equal和is_not_equal也需要比较实部和虚部

2.2：

没有。abs是非成员函数不是友元函数

2.3：

需要访问多个对象的为私有成员，提供特殊功能的非成员函数

问题3：

class Complex {
private:
    double real;
    double imag;

public:
    Complex(const Complex& other) = delete;
};

可以以上述代码

实验任务3：

PlayerControl.h:

#pragma once
#include <string>

enum class ControlType { Play, Pause, Next, Prev, Stop, Unknown };

class PlayerControl {
public:
    PlayerControl();
    
    ControlType parse(const std::string& control_str);
    void execute(ControlType cmd) const; 
    static int get_cnt();
private:
    static int total_cnt;
};

PlayerControl.cpp:

#include "PlayerControl.h"
#include <iostream>
#include <algorithm>
#include <cctype>
int PlayerControl::total_cnt = 0;

PlayerControl::PlayerControl() {}

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

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;
}

task3.cpp：

#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();
    return 0;
}

实验结果：

实验4：

Fraction.h

#pragma once
#include <string>

class Fraction {
private:
    int up;   
    int down; 
    void simplify(); 
    int gcd(int a, int b) const;

public:
    static const std::string doc;
    Fraction(int numerator = 0, int denominator = 1);
    Fraction(const Fraction& other);
    int get_up() const;
    int get_down() const;
    Fraction negative() const; 
    friend void output(const Fraction& f);
    friend Fraction add(const Fraction& f1, const Fraction& f2);
    friend Fraction sub(const Fraction& f1, const Fraction& f2);
    friend Fraction mul(const Fraction& f1, const Fraction& f2);
    friend Fraction div(const Fraction& f1, const Fraction& f2);
};
void output(const Fraction& f);
Fraction add(const Fraction& f1, const Fraction& f2);
Fraction sub(const Fraction& f1, const Fraction& f2);
Fraction mul(const Fraction& f1, const Fraction& f2);
Fraction div(const Fraction& f1, const Fraction& f2);

Fraction.cpp

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

using namespace std;
const string Fraction::doc = "Fraction类 v0.01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) 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) return; 
    if (down < 0) {
        up = -up;
        down = -down;
    }
    int common = gcd(up, down);
    if (common != 0) {
        up /= common;
        down /= common;
    }
}
Fraction::Fraction(int numerator, int denominator) : up(numerator), down(denominator) {
    if (down == 0) {
        throw invalid_argument("分母不能为0");
    }
    simplify();
}

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

task4.cpp

#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() {
    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;
    
    try {
        Fraction result = div(f6, f7);
        cout << "f6 / f7 = "; output(result); cout << endl;
    } catch (const invalid_argument& e) {
        cout << e.what() << endl;
    }
}

实验结果

我选择的是友元函数方案

友元函数方案可以直接访问私有成员避免平凡调用getter函数