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

T.cpp:

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

const std::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; 
    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 << ")" ;
}     
void func() {
    T t5(42);
    t5.m2 = 2049;
    std::cout << "t5 = "; t5.display(); std::cout << '\n';
    std::cout << "func: T objects'current count: " << T::get_cnt() << std::endl;
}

 

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;
}

运行结果截图：

问题1：

 

不能，func函数未声明，找不到

问题2：

普通构造函数：用来构造默认值为0的T类对象，在无参数或有参数时调用

复制构造函数：用已经存在的对象来构造一个新对象，在传递已经存在的对象时调用

移动构造函数：用来将一个临时对象的资源移到另一个对象，在用临时对象时调用

析构函数：用来清理内存，在对象生命周期结束时自动调用

问题3：

不能，静态成员被重复定义

 

实验任务2

Complex.h:

#pragma once
#include <string>

class Complex{
    public:
        static const std::string doc;
        Complex(double a = 0.0,double b = 0.0);
        Complex(const Complex &c);
        double get_real() const;
        double get_imag() const;
        void add(const Complex &c);
        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;
};
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>

const std::string Complex::doc{"a simplified complex class"};
Complex::Complex(double a,double b):real(a),imag(b){
}
Complex::Complex(const Complex &c):real(c.real),imag(c.imag){
}
double Complex::get_real() const{
    return real;
}
double Complex::get_imag() const{
    return imag;
}
void Complex::add(const Complex &c){
    real += c.real;
    imag += c.imag;
}
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 std::sqrt(c.real * c.real + c.imag * c.imag);
}
Complex add(const Complex &c1,const Complex &c2){
    Complex t;
    t.real = c1.real + c2.real;
    t.imag = c1.imag + c2.imag;
    return t;
}
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 (c1.real != c2.real)||(c1.imag !=c2.imag);
}

task2.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();
}

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;
}

运行结果截图：

问题1：

标准库模板类complex更简洁；函数和运算内在有关联，都是数学上的运算

问题2：

2-1：是，它们需要访问real和imag来进行计算和输出

2-2：否，abs通过real()和imag()成员函数来获取实部和虚部

2-3：在需要多次访问私有成员时可以用友元

问题3：

给复制构造函数加上=delete

 

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>   

int PlayerControl::total_cnt = 0;

PlayerControl::PlayerControl() {}

ControlType PlayerControl::parse(const std::string& control_str) {
    std::string s;
    for(auto c: control_str){
        s += std::tolower(c);
    }
     if(s == "play"){
         total_cnt++;
         return ControlType::Play;
     }
     else if(s == "pause"){
         total_cnt++;
         return ControlType::Pause;
     }
     else if(s == "next"){
         total_cnt++;
         return ControlType::Next;
     }
     else if(s == "prev"){
         total_cnt++;
         return ControlType::Prev;
     }
     else if(s == "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;
}

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();
}

 运行结果截图：

 

实验任务4

Fraction.h:

#pragma once
#include <string>

class Fraction{
    public:
        static const std::string doc;
        Fraction(int a = 0,int b = 1);
        Fraction(const Fraction &f);
        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);
    private:
        int up;
        int down;
};
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 <algorithm>
#include <math.h>

const std::string Fraction::doc{"Fraction类v 0.01版.\n目前仅支持分数对象的构造、输出、加/减/乘/除运算."};
void func(int &a,int &b){
    if(a == 0||b == 0){
        return;
    }
    if(b < 0){
        a = -a;
        b = -b;
    }
    int a1 = std::abs(a);
    int b1 = std::abs(b);
    int t;
    do{
        t = a1 % b1;
        a1 = b1;
        b1 = t;
    }while(t != 0);
    a /= a1;
    b /= a1;
}
Fraction::Fraction(int a,int b):up(a),down(b){
    func(a,b);
}
Fraction::Fraction(const Fraction &f):up(f.up),down(f.down){}
int Fraction::get_up() const{
    int a = up;
    int b = down;
    func(a,b); 
    return a;
}
int Fraction::get_down() const{
    int a = up;
    int b = down;
    func(a,b); 
    return b;
}
Fraction Fraction::negative() const{
    return Fraction(-up,down);
}
void output(const Fraction &f){
    int a = f.up;
    int b = f.down;
    func(a,b);
    if(b == 0){
        std::cout << "分母不能为0";
    }
    else{
        if(a == 0){
            std::cout << "0";
        }
        else{
            if(b == 1){
                std::cout << a;
            }
            else{
                std::cout << a << "/" << b;
            }
        }
    }
}
Fraction add(const Fraction &f1,const Fraction &f2){
    int a = f1.up * f2.down + f2.up * f1.down;
    int b = f1.down * f2.down;
    func(a,b);
    return Fraction(a,b);
}
Fraction sub(const Fraction &f1,const Fraction &f2){
    int a = f1.up * f2.down - f2.up * f1.down;
    int b = f1.down * f2.down;
    func(a,b);
    return Fraction(a,b);
}
Fraction mul(const Fraction &f1,const Fraction &f2){
    int a = f1.up * f2.up;
    int b = f1.down * f2.down;
    func(a,b);
    return Fraction(a,b);
}
Fraction div(const Fraction &f1,const Fraction &f2){
    int a = f1.up * f2.down;
    int b = f1.down * f2.up;
    func(a,b);
    return Fraction(a,b);
}

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;
}

运行结果截图：

 

问题1：

友元，可以直接访问Fraction的私有成员