实验二

实验一

源代码

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';
}

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();

test1.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();
    system("pause");
}

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;

}

运行截图

问题回答

1. 报错，截图如下：
   
   意思是 func函数没有在范围内声明。
   窃以为，当我们删去Line36行的func定义时，类内部的友元就无法识别func已经声明过，从而编译出错，因此出现了报错的情况；
2. • 普通构造函数在创建变量的时候调用，无论是创建空变量还是带有参数值的变量；
   • 复制构造函数在创建变量的时候，但是传入的是该类的变量的时候使用 s1(s2)，这样相当于把s2拷贝到了s1中；
   • 移动构造函数在进行 move操作的时候，负责将右值传递给新的变量；
   • 析构函数则在程序退出时自动销毁内存中的变量。
3. 编译失败，截图如下：
   
   移动代码后，移动的函数在h中被定义两次，程序出现了重复定义，因此出错。

实验二

源代码

Complex.h

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

class Complex {
public:
    static constexpr const char* doc = "A Simplified Complex Class";

    Complex(): real_(0.0), imag_(0.0) {};
    Complex(double real, double imag = 0.0): real_(real), imag_(imag) {};
    Complex(const Complex& other) = default;

    double get_real() const;
    double get_imag() const;

    void add(const Complex& other);
    friend bool is_equal(const Complex& c1 , const Complex& c2);
    friend bool is_not_equal(const Complex& c1 , const Complex& c2);
    friend Complex add(const Complex& c1, const Complex& c2);
    friend double abs(const Complex& c);
    friend void output(const Complex& c);

private:
    double real_;
    double imag_;
};

Complex.cpp

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

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_;
}

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);
}

Complex add(const Complex& c1, const Complex& c2){
    return Complex(c1.real_ + c2.real_, c1.imag_ + c2.imag_);
}

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

void output(const Complex& c){
    if (c.imag_ >= 0)
    {
        std::cout << std::setw(2) << c.real_ << " + " << c.imag_ << "i";
    }
    else
    {
        std::cout << std::setw(2) << c.real_ << " - " << -c.imag_ << "i";
    }
}

test2.cpp

// 待补足头文件
#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();

    system("pause");
}

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;
}

运行截图

问题回答

1. 单看stl和custom版本的complex类，个人感觉其实stl更加的简洁，它不需要你调用函数，而是和一个C++“本来就有的”数据结构一样去调用它（至少，你写add肯定比“+”要更加繁琐）至于函数与运算的内在关联，我感觉运算更加简洁，它存在于一套编程语言的底层，比函数层级更基础。运算符是构成函数的基础之一，而函数又可以通过基础运算符实现更加复杂的运算，两者相互依存，不可分割。

• 是的，因为涉及运算和显示确实需要访问实部和虚部；通过函数进行访问并完成一样的操作显然过于复杂；
• 不是，在complex中有相关接口，不需要。
• 在迫不得已需要直接访问私有成员的时候可以考虑使用friend，一般情况下还是最好是公共类型提供接口；

3. 直接禁用复制构造函数可以禁用“=”，但是显然脱离题意，这样的话复制操作完全被禁用了。还有一种办法 MyClass& operator=(const MyClass&) = delete; 这样的话直接禁用了“=”操作符。

实验三

源代码

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

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
    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;   
};

test3.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();
}

编译命令（额外附加）

clang++ task3.cpp PlayerControl.cpp -o app -std=c++11

运行截图

问题回答

• 额，其实修改一下编码就可以了，把编码修改成utf-8，然后直接在打印界面，找个emoji贴上去就可以了，由于本项目是基于GBK的编码格式，一定要提前转码！

实验四

源代码

Fraction.cpp

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

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."};

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

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

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

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

Fraction add(const Fraction& f1 , const Fraction& f2){
    Fraction sum((f1.up*f2.down+f1.down*f2.up),(f1.down*f2.down));
    return sum;
}

Fraction sub(const Fraction& f1 , const Fraction& f2){
    return add(f1,f2.negative());
}

void output(const Fraction& f) {
    if (f.up == 0) {
        std::cout << 0;
    } else if (f.down == 1) {
        std::cout << f.up;
    } else {
        std::cout << f.up << "/" << f.down;
    }
}

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

Fraction div(const Fraction& f1, const Fraction& f2) {
    if (f2.up == 0 || f2.down == 0) {
        throw std::invalid_argument("除数不能为0");
    }
    int newUp = f1.up * f2.down;
    int newDown = f1.down * f2.up;
    return Fraction(newUp, newDown); 
}

Fraction.h

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

class Fraction
{
private:
    int up;
    int down;
    int gcd(int a, int b) const;
public:
    static const std::string doc;
    Fraction()=delete;
    Fraction(int i_up,int i_down=1):up{i_up},down{i_down}{
        if (down < 0)
        {
            down = -down;
            up = -up;
        }
        if (down == 0)
        {
            throw std::invalid_argument("分母不能为0");
        }
        int commonDivisor = gcd(up, down);
        up /= commonDivisor;
        down /= commonDivisor;
    };
    Fraction(const Fraction& others)=default;

    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);
};

运行截图

问题回答

友元，相对方便且易于管理

实验总结

1. 本次实验做的还是比较头大的qwq，第一个是方法的编写上还是保留了函数的固有思维，一直在头疼于找参数，其实直接用private就可以了；还有就是doc的初始化，非常坐牢qwq，编译器一直报错，一直分不清static和const在哪里写；
2. 有点收获：前两个实验是机房做的，用的编译器是g++；后两个是在图书馆用我的备用机macbook air（x86框架）做的，用的是clang++编译器，我也算都了解了一下如何用powershell和terminal编译（），还有就是感觉要好好恶补一下英语，报错信息看不懂（）