实验二

#任务1

##代码

###T.h

#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();

###T.cpp

#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';
}

###Task.cpp

#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;
}

##运行测试截图

 

##问题回答

###问题1 YES

###问题2   普通构造函数T(int x = 0, int y = 0)

                     功能：使用给定的 x 和 y 初始化 m1 和 m2 成员。如果调用时没有提供参数，则使用默认值 (0, 0) 

                     调用时机：

                  复制构造函数 T(const T &t)

                      功能：用另一个同类型对象 t 的成员值来初始化新对象的成员

                      调用时机：用一个已有对象初始化新对象时或函数按值传参

                  移动构造函数 T(T &&t)

                      功能：从临时对象（右值）t 中“窃取”资源

                      调用时机：用临时对象（右值）初始化新对象函数或返回局部对象

                  析构函数 ~T()

                     功能：清理对象的资源

                     调用时机：当对象离开其作用域，通过delete操作释放动态分配的对象时被调用

###问题3 能

#任务2

##代码

Complex.h

#pragma once
  #include <string>
  
  class Complex {
  public:
      static const std::string doc;
      Complex(double real = 0.0, double imag = 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);
 
 private:
     double real;
     double imag;
};

Complex.cpp

#include "Complex.h"
 #include <cmath>
 #include <iostream>
  
  // 类属性初始化
  const std::string Complex::doc = "a simplified Complex class";
  
  // 构造函数实现
  Complex::Complex(double real, double imag) : real(real), imag(imag) {}
  Complex::Complex(const Complex& other) : real(other.real),  imag(other.imag) {}
 
 // 对象方法实现
 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;
 }
 
 // 友元函数实现
 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);
 }

task2.cpp

#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*******\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;
}

##运行测试截图

 

 ##问题回答

###问题1  标准库模板类complex更简洁；有关联

###问题2

    2.1 是，可以通过设置为friend实现

    2.2  是

    2.3需要直接访问类的私有成员

###问题3 将拷贝赋值运算符设为私有

#任务3

##代码

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);   // 实现std::string --> ControlType转换ControlTypeת��
    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;   
};

PlayerControl.cpp

#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 = control_str;
std::transform(lower_str.begin(),lower_str.end(),lower_str.begin(),::tolower);

    total_cnt++;
    if (lower_str == "play") 
        return ControlType::Play;
    else if (lower_str == "pause") 
        return ControlType::Pause;
    else if (lower_str == "next") 
        return ControlType::Next;
    else if (lower_str == "prev") 
        return ControlType::Prev;
    else if (lower_str == "stop") 
        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();
}

##运行测试截图

 

#任务4

##代码

Fraction.h

#pragma once
#include <string>

class Fraction {
public:
    Fraction(int up = 0, int down = 1);
    Fraction(const Fraction& f);
    int get_up() const;
    int get_down() const;
    Fraction negative() const;
    static const std::string doc;

private:
    int up, down;
    void simplify();

    friend void output(const Fraction& f);
    friend Fraction add(const Fraction& a, const Fraction& b);
    friend Fraction sub(const Fraction& a, const Fraction& b);
    friend Fraction mul(const Fraction& a, const Fraction& b);
    friend Fraction div(const Fraction& a, const Fraction& b);
};

Fraction.cpp

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

const std::string Fraction::doc = "Fraction类 v0.01版";

Fraction::Fraction(int u, int d): up{u}, down{d} {
    if (down == 0) throw std::invalid_argument("Denominator cannot be zero");
    simplify();
}

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

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

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) {
    std::cout << f.up << "/" << f.down;
}

Fraction add(const Fraction& a, const Fraction& b) {
    return Fraction(a.up * b.down + b.up * a.down, a.down * b.down);
}

Fraction sub(const Fraction& a, const Fraction& b) {
    return Fraction(a.up * b.down - b.up * a.down, a.down * b.down);
}

Fraction mul(const Fraction& a, const Fraction& b) {
    return Fraction(a.up * b.up, a.down * b.down);
}

Fraction div(const Fraction& a, const Fraction& b) {
    if (b.up == 0) throw std::invalid_argument("Division by zero");
    return Fraction(a.up * b.down, a.down * b.up);
}

task4.cpp

#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;
}

##运行测试截图

##问题回答

友元，友元函数可以访问类的私有成员，可以实现复杂的运算逻辑