实验二

任务一

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;
}

效果

 问题

1.

 不行，在作用域内没有声明func函数, 因为 func() 是类外定义的友元函数，必须先声明.

2.

普通构造：分配内存并初始化成员；创建新T对象且传整型参数时调用。
复制构造：拷贝对象；用已有对象初始化新对象时调用。
移动构造：转移资源；用右值初始化时调用。
析构：释放内存并清理；对象生存期结束时调用。

3.

 不能正确编译，会报多重定义错误。原因是类的静态成员定义应放在.cpp文件，若剪切到.h头文件，多文件包含时会重复定义。

任务二

代码

#pragma once
#include <string>

class Complex {
public:
    static const std::string doc;

public:
    Complex() : real(0.0), imag(0.0) {}
    Complex(double real_val) : real(real_val), imag(0.0) {}
    Complex(double real_val, double imag_val) : real(real_val), imag(imag_val) {}
    Complex(const Complex& other) : real(other.real), imag(other.imag) {}

public:
    double get_real() const { return real; }
    double get_imag() const { return imag; }
    void add(const Complex& other) {
        real += other.real;
        imag += other.imag;
    }

public:
    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);

private:
    double real;
    double imag;
};

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

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

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

#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;

}

效果

 

 问题

1.标准库complex更简洁，因重载运算符，操作形式同普通运算；自定义用函数调用。二者功能一致，形式差异源于运算符重载。

2-1：是，因需访问私有成员。
2-2：不是，标准库通过public成员函数访问数据。

2-3：非成员函数需访问类私有或者保护成员时用友元，平衡功能与数据保护。

3.将类Complex的复制构造函数声明为delete，即Complex(const Complex&) = delete;。

任务三

代码

#pragma once
#include <string>

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

class PlayerControl {
public:
    PlayerControl();

    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）       

    static int get_cnt();

private:
    static int total_cnt;
};

#include "PlayerControl.h"
#include <iostream>
#include <algorithm>
#include <cctype>  // 用于字符小写转换

int PlayerControl::total_cnt = 0;

PlayerControl::PlayerControl() {}

ControlType PlayerControl::parse(const std::string& control_str) {
    // 转换输入字符串为小写，实现大小写不敏感
    std::string lower_cmd = control_str;
    std::transform(lower_cmd.begin(), lower_cmd.end(), lower_cmd.begin(),
        [](unsigned char c) { return std::tolower(c); });

    // 匹配有效命令并处理计数
    if (lower_cmd == "play") {
        total_cnt++;
        return ControlType::Play;
    }
    else if (lower_cmd == "pause") {
        total_cnt++;
        return ControlType::Pause;
    }
    else if (lower_cmd == "next") {
        total_cnt++;
        return ControlType::Next;
    }
    else if (lower_cmd == "prev") {
        total_cnt++;
        return ControlType::Prev;
    }
    else if (lower_cmd == "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;
}

#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();
}

效果

 任务四

代码

#pragma once
#include <string>
#include <iostream>

class Fraction {
private:
    int up;
    int down;
    void simplify();

public:
    static const std::string doc;

    Fraction(int u);
    Fraction(int u, int d);
    Fraction(const Fraction& other);

    int get_up() const;
    int get_down() const;
    Fraction negative() const;
};

namespace FracCal {
    namespace Internal {
        int gcd(int a, int b);
    }

    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);
}

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

const std::string Fraction::doc{ "Fraction类 v 0.01版. 目前仅支持分数对象的构造､输出､加/减/乘/除运算." };

void Fraction::simplify() {
    if (down == 0) return;

    if (down < 0) {
        up *= -1;
        down *= -1;
    }

    int g = FracCal::Internal::gcd(std::abs(up), std::abs(down));
    if (g != 0) {
        up /= g;
        down /= g;
    }
}

Fraction::Fraction(int u) : up(u), down(1) {
    simplify();
}

Fraction::Fraction(int u, int d) : up(u), down(d) {
    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);
}

namespace FracCal {
    namespace Internal {
        int 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 output(const Fraction& f) {
        if (f.get_down() == 0) {
            std::cout << "分母不能为0";
        }
        else if (f.get_up() == 0) {
            std::cout << 0;
        }
        else if (f.get_up() % f.get_down() == 0) {
            std::cout << f.get_up() / f.get_down();
        }
        else {
            std::cout << f.get_up() << "/" << f.get_down();
        }
        std::cout << std::endl;
    }

    Fraction add(const Fraction& f1, const Fraction& f2) {
        int common_down = f1.get_down() * f2.get_down() / Internal::gcd(f1.get_down(), f2.get_down());
        int new_up = f1.get_up() * (common_down / f1.get_down()) + f2.get_up() * (common_down / f2.get_down());
        return Fraction(new_up, common_down);
    }

    Fraction sub(const Fraction& f1, const Fraction& f2) {
        int common_down = f1.get_down() * f2.get_down() / Internal::gcd(f1.get_down(), f2.get_down());
        int new_up = f1.get_up() * (common_down / f1.get_down()) - f2.get_up() * (common_down / f2.get_down());
        return Fraction(new_up, common_down);
    }

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

    Fraction div(const Fraction& f1, const Fraction& f2) {
        if (f2.get_up() == 0) {
            return Fraction(0, 0);
        }
        int new_up = f1.get_up() * f2.get_down();
        int new_down = f1.get_down() * f2.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);
    Fraction f3(-18, 12);
    Fraction f4(f3);

    cout << "f1 = "; FracCal::output(f1);
    cout << "f2 = "; FracCal::output(f2);
    cout << "f3 = "; FracCal::output(f3);
    cout << "f4 = "; FracCal::output(f4);

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

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

void test2() {
    using std::cout;
    using std::endl;

    Fraction f6(42, 55);
    Fraction f7(0, 3);
    cout << "f6 = "; FracCal::output(f6);
    cout << "f7 = "; FracCal::output(f7);
    cout << "f6 / f7 = "; FracCal::output(FracCal::div(f6, f7));
}

效果

 问题

1. 设计方案：命名空间+自由函数
2. 决策理由：
避免友元破坏封装，通过`get_up()`/`get_down()`访问数据即可；
比静态成员函数更灵活，不使`Fraction`类职责过载，维护性强。
3. 方案对比：友元：快捷但耦合高；
静态成员函数：类内过载；
命名空间+自由函数：封装好、易维护，适配分数运算场景。