实验二

任务一

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';
}

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：

T.h中，在类T内部，已声明 func 是T的友元函数。在类外部，去掉line36，重新编译，程序能否正常运行。

不能友元函数声明不是真正的函数声明，需要独立声明

问题2：

T.h中，line9-12给出了各种构造函数、析构函数。总结它们各自的功能、调用时机

T(int x = 0, int y = 0)是普通构造函数，创建对象时将其初始化，在创建新对象时调用
T(const T &t)是复制构造函数，用一个对象去初始化另一个同类型的新对象，复制已有对象时调用
T(T &&t)是移动构造函数，引用右值初始化新对象，移动已有对象时调用
~T()是析构函数，对象被删除前清理，对象生命周期结束时调用

问题3：

T.cpp中，line13-15，剪切到T.h的末尾，重新编译，程序能否正确编译。

不能 task1.cpp和T.cpp两个重复定义

任务二

Complex.h

#ifndef COMPLEX_H
#define COMPLEX_H

#include <string>
#include <iostream>

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

    // 构造函数
    Complex();                       
    Complex(double real);             
    Complex(double real, double imag);  
    Complex(const Complex& other);   

    // 接口：获取实部和虚部
    double get_real() const;
    double get_imag() const;

    // 成员函数
    void add(const Complex& other);

    // 友元函数
    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;
};

#endif // COMPLEX_H

Complex.cpp

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

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

Complex::Complex() : real(0.0), imag(0.0) {}

Complex::Complex(double real) : real(real), imag(0.0) {}

Complex::Complex(double real, double imag) : real(real), imag(imag) {}

Complex::Complex(const Complex& other) : real(other.real), imag(other.imag) {}

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;
}

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) {
    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 "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\n";
    test_Complex();

    std::cout << "\n******测试2：标准库模板类complex******\n\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：
比较自定义类 Complex 和标准库模板类 complex 的用法，在使用形式上，哪一种更简洁？函数和运算内在有关
联吗？

标准库模板类complex用法更简洁函数和运算逻辑上相关联

问题2：

2-1：自定义 Complex 中, output/abs/add/ 等均设为友元，它们真的需要访问私有数据吗？（回答“是/否”并

给出理由）

是要访问私有成员real和imag

2-2：标准库 std::complex 是否把 abs 设为友元？（查阅 cppreference后回答）

否

2-3：什么时候才考虑使用 friend？总结你的思考。

外部函数需要访问私有成员时使用

问题3：

如果构造对象时禁用=形式，即遇到 Complex c4 = c2; 编译报错，类Complex的设计应如何调整？

改为Complex(const Complex&) = delete

任务三

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;   
};

PlayerControl.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 str = control_str;
    std::transform(str.begin(), str.end(), str.begin(),
                   [](unsigned char c) { return std::tolower(c); });
    

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

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

任务四

Fraction.h

#pragma once
#include<string>
class Fraction{
    public:
        Fraction(int up=0,int down=1);
        Fraction(const Fraction &f):up(f.up),down(f.down){}
        Fraction(){}
        int get_up()const{
             return up;
        }
        int get_down()const{
            return down;
        }
        Fraction negative()const;
    private:
        int up,down;
    public:
        static const std::string doc;
    private:
        void func();
        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);        
};
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<cmath>
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.";
Fraction::Fraction(int up,int down):up(up),down(down){
    func();
}
Fraction Fraction::negative()const{
    return Fraction(-up,down);
}
void Fraction::func(){
    if(up>0&&down<0){
    up=-up;
    down=-down;
    }
    else if(up<0&&down<0){
    up=-up;
    down=-down;
    }
    int i,a,b;
    a=up;
    b=down;
    a=std::abs(a);
    b=std::abs(b);
    while(b!=0){
    i=b;
    b=a%b;
    a=i;
    }
    up/=a;
    down/=a;
}
void output(const Fraction &f){
    if(f.up==0){
        std::cout<<"0"<<std::endl;
    }
    else if(f.down==1){
        std::cout<<f.up<<std::endl;
    }
    else if(f.down>0){
        std::cout<<f.up<<"/"<<f.down<<std::endl;
    }
    else if(f.up>0&&f.down<0){
        std::cout<<"-"<<f.up<<"/"<<f.down<<std::endl;
    }
    else if(f.up<0&&f.down<0){
        std::cout<<f.up<<"/"<<f.down<<std::endl;
    }
}
Fraction add(const Fraction &f1,const Fraction &f2){
    return Fraction(f1.up*f2.down+f1.down*f2.up,f1.down*f2.down);
}
Fraction sub(const Fraction &f1,const Fraction &f2){
    return Fraction(f1.up*f2.down-f1.down*f2.up,f1.down*f2.down);
}        
Fraction mul(const Fraction &f1,const Fraction &f2){
    return Fraction(f1.up*f2.up,f1.down*f2.down);
}
Fraction div(const Fraction &f1,const Fraction &f2){
    if(f2.up==0){
        std::cout<<"分母不能为0"<<std::endl; 
    }
    return Fraction(f1.up*f2.down,f1.down*f2.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;
}

运行结果截图

分数的输出和计算， output/add/sub/mul/div ，你选择的是哪一种设计方案？（友元/自由函数/命名空间+自

由函数/类+static)

选友元方案可直接访问私有成员更简洁

posted @ 2025-10-28 22:20 yuu77 阅读(5) 评论(1) 收藏举报

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实验二

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