实验二

任务1：

源代码task1.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;
}

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';
}

运行结果截图：

问题1：YES

问题2：普通构造函数初始化对象，复制构造函数用已有对象初始化新对象，移动构造函数转移右值对象资源，析构函数清理对象资源，它们分别在对象创建、拷贝 / 传值返回、右值初始化、对象生命周期结束时调用。

问题3：YES

任务2：

源代码task3.cpp

#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();
    return 0;
}

void test_Complex() {
    using namespace std;
    cout << "类成员测试：\n";
    cout << Complex::doc << "\n\n";
    cout << "Complex对象测试：\n";
    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() << "\n\n";
    cout << "复数运算测试：\n";
    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;
    Complex c6 = add(c2, c3);
    cout << "c4 = c2 + c3, c4 = "; output(c6); cout << endl;
}

void test_std_complex() {
    using namespace std;
    cout << "std::complex<double>对象测试：\n";
    complex<double> c1;
    complex<double> c2(3, -4);
    complex<double> c3(c2);
    complex<double> c4 = c2;
    const 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() << "\n\n";
    cout << "复数运算测试：\n";
    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;
    complex<double> c6 = c2 + c3;
    cout << "c4 = c2 + c3, c4 = " << c6 << endl;
}

Complex.cpp

#include "Complex.h"
#include <cmath>
const std::string Complex::doc = "a simplified complex class";
Complex::Complex() : rea(0.0), imag(0.0) {}
Complex::Complex(double r) : rea(r), imag(0.0) {}
Complex::Complex(double r, double i) : rea(r), imag(i) {}
Complex::Complex(const Complex& other) : rea(other.rea), imag(other.imag) {}
double Complex::get_real() const {
    return rea;
}
double Complex::get_imag() const {
    return imag;
}
void Complex::add(const Complex& other) {
    rea += other.rea;
    imag += other.imag;
}
double abs(const Complex& c) {
    return std::sqrt(c.rea * c.rea + c.imag * c.imag);
}
Complex add(const Complex& c1, const Complex& c2) {
    Complex res;
    res.rea = c1.rea + c2.rea;
    res.imag = c1.imag + c2.imag;
    return res;
}
bool is_equal(const Complex& c1, const Complex& c2) {
    return (c1.rea == c2.rea) && (c1.imag == c2.imag);
}
bool is_not_equal(const Complex& c1, const Complex& c2) {
    return !is_equal(c1, c2);
}
void output(const Complex& c) {
    if (c.imag >= 0) {
        std::cout << c.rea << " + " << c.imag << "i";
    } else {
        std::cout << c.rea << " - " << -c.imag << "i";
    }
}

Complex.h

#ifndef COMPLEX_H
#define COMPLEX_H
#include <string>
#include <iostream>
class Complex {
public:
    static const std::string doc;
    Complex();
    Complex(double r);
    Complex(double r, double i);
    Complex(const Complex& other);
    double get_real() const;
    double get_imag() const;
    void add(const Complex& other);
    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);
    friend void output(const Complex& c);
private:
    double rea;
    double imag;
};
#endif

运行结果截图

问题一：标准库模板类complex更简洁，有。

问题二：2-1：是。因为output需访问私有数据输出，abs需访问私有数据计算模长，add需访问私有数据进行复数相加，所以必须通过友元访问私有成员。

2-2：是

2-3：否。std::complex通过公有成员函数real()和imag()提供实部和虚部的访问。

问题三：在类Complex中显式删除复制构造函数，声明为Complex(const Complex&) = delete;，这样当出现Complex c4 = c2;形式的构造时，编译器会报错，从而禁用该构造形式。

任务3：

源代码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();
}

PlayControl.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); });
    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;
    } else {
        result = ControlType::Unknown;
    }
    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;
}

PlayControl.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;
}; 

运行结果截图

任务4：

源代码task4.cpp