实验2 现代C++编程初体验

1. 实验任务1

T.h

 1 #pragma once
 2 
 3 #include <string>
 4 
 5 // 类T: 声明
 6 class T {
 7 // 对象属性、方法
 8 public:
 9     T(int x = 0, int y = 0);   // 普通构造函数
10     T(const T &t);  // 复制构造函数
11     T(T &&t);       // 移动构造函数
12     ~T();           // 析构函数
13 
14     void adjust(int ratio);      // 按系数成倍调整数据
15     void display() const;           // 以(m1, m2)形式显示T类对象信息
16 
17 private:
18     int m1, m2;
19 
20 // 类属性、方法
21 public:
22     static int get_cnt();          // 显示当前T类对象总数
23 
24 public:
25     static const std::string doc;       // 类T的描述信息
26     static const int max_cnt;           // 类T对象上限
27 
28 private:
29     static int cnt;         // 当前T类对象数目
30 
31 // 类T友元函数声明
32     friend void func();
33 };
34 
35 // 普通函数声明
36 void func();

T.cpp

 1 #include "T.h"
 2 #include <iostream>
 3 #include <string>
 4 
 5 // 类T实现
 6 
 7 // static成员数据类外初始化
 8 const std::string T::doc{"a simple class sample"};
 9 const int T::max_cnt = 999;
10 int T::cnt = 0;
11 
12 // 类方法
13 
14 // 对象方法
15 T::T(int x, int y): m1{x}, m2{y} { 
16     ++cnt; 
17     std::cout << "T constructor called.\n";
18 } 
19 
20 T::T(const T &t): m1{t.m1}, m2{t.m2} {
21     ++cnt;
22     std::cout << "T copy constructor called.\n";
23 }
24 
25 T::T(T &&t): m1{t.m1}, m2{t.m2} {
26     ++cnt;
27     std::cout << "T move constructor called.\n";
28 }    
29 
30 T::~T() {
31     --cnt;
32     std::cout << "T destructor called.\n";
33 }           
34 
35 void T::adjust(int ratio) {
36     m1 *= ratio;
37     m2 *= ratio;
38 }    
39 
40 void T::display() const {
41     std::cout << "(" << m1 << ", " << m2 << ")" ;
42 }     
43 
44 // 普通函数实现
45 void func() {
46     T t5(42);
47     t5.m2 = 2049;
48     std::cout << "t5 = "; t5.display(); std::cout << '\n';
49 }
50 
51 int T::get_cnt() {
52     return cnt;
53 }

task1.cpp

 1 #include "T.h"
 2 #include <iostream>
 3 
 4 void test_T();
 5 
 6 int main() {
 7     std::cout << "test Class T: \n";
 8     test_T();
 9 
10     std::cout << "\ntest friend func: \n";
11     func();
12 }
13 
14 void test_T() {
15     using std::cout;
16     using std::endl;
17 
18     cout << "T info: " << T::doc << endl;
19     cout << "T objects'max count: " << T::max_cnt << endl;
20     cout << "T objects'current count: " << T::get_cnt() << endl << endl;
21 
22     T t1;
23     cout << "t1 = "; t1.display(); cout << endl;
24 
25     T t2(3, 4);
26     cout << "t2 = "; t2.display(); cout << endl;
27 
28     T t3(t2);
29     t3.adjust(2);
30     cout << "t3 = "; t3.display(); cout << endl;
31 
32     T t4(std::move(t2));
33     cout << "t4 = "; t4.display(); cout << endl;
34 
35     cout << "test: T objects'current count: " << T::get_cnt() << endl;
36 }

运行结果截图:

image

 

问题1：不能

问题2：

 普通构造函数
功能：用来初始化T的对象，为成员变量m1，m2赋初始值

调用时机：在创建类T的对象时调用

 复制构造函数
​功能​：创建对象的完整副本，保持原始对象不变

调用时机：用一个对象初始化另一个对象时

 移动构造函数

​功能​：转移右值对象的资源，将源对象置于可析构状态

调用时机：用右值初始化对象的时候

 析构函数

​功能​：递减对象计数器，执行资源清理

​调用时机：对象生命周期结束时自动调用

问题3：不能

image 原因：编译时，task1.cpp 和 T.cpp都会包含 T.h 中的这些定义，会发现 T::doc, T::max_cnt, T::cnt 有两个重复的定义,因此报"多重定义"错误

2. 实验任务2

 Complex.h

 1 #pragma once
 2 
 3 #include <string>
 4 
 5 class Complex{
 6     public:
 7         Complex(double a = 0,double b = 0);
 8         Complex(const Complex &c);
 9         ~Complex();
10     private:
11         double real, imag;
12     
13     public:
14         double get_real() const;
15         double get_imag() const;
16         void add(const Complex &c) ;
17         
18     public:
19         static const std::string doc;
20         
21     friend void output();
22     friend double abs();
23     friend Complex add();
24     friend bool is_equal();
25     friend bool is_not_equal();
26 };
27 
28 void output(const Complex &c);
29 double abs(const Complex &c);
30 Complex add(const Complex &c1, const Complex &c2);
31 bool is_equal(const Complex &c1, const Complex &c2);
32 bool is_not_equal(const Complex &c1, const Complex &c2);

Complex.cpp

 1 #include "Complex.h"
 2 
 3 #include <iostream>
 4 #include <string>
 5 #include <cmath>
 6 
 7 const std::string Complex::doc{"a simplified complex class"};
 8 Complex::Complex(double a, double b){
 9     real = a;  imag = b;
10 }
11 Complex::Complex(const Complex &c){
12     real = c.real; imag = c.imag ;
13 }
14 
15 Complex::~Complex(){
16 }
17 double Complex::get_real() const{
18     return real;
19 }
20 double Complex::get_imag()const{
21     return imag;
22 }
23 
24 void Complex::add(const Complex &c) {
25     real += c.real ;
26     imag += c.imag ;
27 }
28 
29 void output(const Complex &c){
30     if(c.get_imag() >= 0)
31         std::cout << c.get_real() << " + " << c.get_imag() << "i" << std::endl;
32     else
33         std::cout << c.get_real() << " - " << abs(c.get_imag())<< "i" << std::endl;
34 }
35 
36 double abs(const Complex &c){
37     return sqrt(c.get_real()*c.get_real() + c.get_imag()*c.get_imag());
38 }
39 
40 Complex add(const Complex &c1, const Complex &c2){
41     Complex c(c1.get_real()+c2.get_real() ,c1.get_imag()+c2.get_imag());
42     return c;
43 }
44 
45 bool is_equal(const Complex &c1, const Complex &c2){
46     if(c1.get_real() == c2.get_real() && c1.get_imag() == c2.get_imag())
47         return true;
48     else
49         return false;
50 }
51 
52 bool is_not_equal(const Complex &c1, const Complex &c2){
53     if(c1.get_real() == c2.get_real() && c1.get_imag() == c2.get_imag())
54         return false;
55     else
56         return true;
57 }

task2.cpp

 1 #include "Complex.h"
 2 #include <iostream>
 3 #include <iomanip>
 4 #include <complex>
 5 
 6 void test_Complex();
 7 void test_std_complex();
 8 
 9 int main() {
10     std::cout << "*******测试1: 自定义类Complex*******\n";
11     test_Complex();
12 
13     std::cout << "\n*******测试2: 标准库模板类complex*******\n";
14     test_std_complex();
15 }
16 
17 void test_Complex() {
18     using std::cout;
19     using std::endl;
20     using std::boolalpha;
21 
22     cout << "类成员测试: " << endl;
23     cout << Complex::doc << endl << endl;
24 
25     cout << "Complex对象测试: " << endl;
26     Complex c1;
27     Complex c2(3, -4);
28     Complex c3(c2);
29     Complex c4 = c2;
30     const Complex c5(3.5);
31 
32     cout << "c1 = "; output(c1); cout << endl;
33     cout << "c2 = "; output(c2); cout << endl;
34     cout << "c3 = "; output(c3); cout << endl;
35     cout << "c4 = "; output(c4); cout << endl;
36     cout << "c5.real = " << c5.get_real() 
37          << ", c5.imag = " << c5.get_imag() << endl << endl;
38 
39     cout << "复数运算测试: " << endl;
40     cout << "abs(c2) = " << abs(c2) << endl;
41     c1.add(c2);
42     cout << "c1 += c2, c1 = "; output(c1); cout << endl;
43     cout << boolalpha;
44     cout << "c1 == c2 : " << is_equal(c1, c2) << endl;
45     cout << "c1 != c2 : " << is_not_equal(c1, c2) << endl;
46     c4 = add(c2, c3);
47     cout << "c4 = c2 + c3, c4 = "; output(c4); cout << endl;
48 }
49 
50 void test_std_complex() {
51     using std::cout;
52     using std::endl;
53     using std::boolalpha;
54 
55     cout << "std::complex<double>对象测试: " << endl;
56     std::complex<double> c1;
57     std::complex<double> c2(3, -4);
58     std::complex<double> c3(c2);
59     std::complex<double> c4 = c2;
60     const std::complex<double> c5(3.5);
61 
62     cout << "c1 = " << c1 << endl;
63     cout << "c2 = " << c2 << endl;
64     cout << "c3 = " << c3 << endl;
65     cout << "c4 = " << c4 << endl;
66 
67     cout << "c5.real = " << c5.real() 
68          << ", c5.imag = " << c5.imag() << endl << endl;
69 
70     cout << "复数运算测试: " << endl;
71     cout << "abs(c2) = " << abs(c2) << endl;
72     c1 += c2;
73     cout << "c1 += c2, c1 = " << c1 << endl;
74     cout << boolalpha;
75     cout << "c1 == c2 : " << (c1 == c2)<< endl;
76     cout << "c1 != c2 : " << (c1 != c2) << endl;
77     c4 = c2 + c3;
78     cout << "c4 = c2 + c3, c4 = " << c4 << endl;
79 }

问题1：标准库模板类complex，有关联。

问题2：
2-1：output/abs/add/等均需对私有数据进行一定的操作，必须要访问私有数据。
2-2：不是，是独立函数。
2-3：当我想要使用某个函数对类的私有数据进行操作，而该函数又不是类的成员函数，无法直接访问私有函数时，可以将该函数设为类的友元函数。
问题3：可以将其设为私有函数
 
3. 实验任务3
PlayerControl.h
 1 #pragma once
 2 #include <string>
 3 
 4 enum class ControlType {Play, Pause, Next, Prev, Stop, Unknown};
 5 
 6 class PlayerControl {
 7 public:
 8     PlayerControl();
 9 
10     ControlType parse(const std::string& control_str);   // 实现std::string --> ControlType转换
11     void execute(ControlType cmd) const;   // 执行控制操作（以打印输出模拟）       
12 
13     static int get_cnt();
14 
15 private:
16     static int total_cnt;   
17 };

PlayerControl.cpp

 1 #include "PlayerControl.h"
 2 #include <iostream>
 3 #include <algorithm>   
 4 
 5 int PlayerControl::total_cnt = 0;
 6 
 7 PlayerControl::PlayerControl() {}
 8 
 9 ControlType PlayerControl::parse(const std::string& control_str) {
10     std::string new_control_str;
11     for(auto c:control_str)
12         new_control_str += tolower(c);
13     new_control_str[0] = toupper(control_str[0]);
14     
15     if(new_control_str == "Play"){
16         total_cnt++;return ControlType::Play;
17     }
18     else if(new_control_str == "Pause"){
19         total_cnt++;return ControlType::Pause;
20     }
21     else if(new_control_str == "Next"){
22         total_cnt++;return ControlType::Next;
23     }
24     else if(new_control_str == "Prev"){
25         total_cnt++;return ControlType::Prev;
26     }
27     else if(new_control_str == "Stop"){
28         total_cnt++;return ControlType::Stop;
29     }
30     else{
31         total_cnt++;return ControlType::Unknown;
32     }
33 }
34 
35 void PlayerControl::execute(ControlType cmd) const {
36     switch (cmd) {
37     case ControlType::Play:  std::cout << "[play] Playing music...\n"; break;
38     case ControlType::Pause: std::cout << "[Pause] Music paused\n";    break;
39     case ControlType::Next:  std::cout << "[Next] Skipping to next track\n"; break;
40     case ControlType::Prev:  std::cout << "[Prev] Back to previous track\n"; break;
41     case ControlType::Stop:  std::cout << "[Stop] Music stopped\n"; break;
42     default:                 std::cout << "[Error] unknown control\n"; break;
43     }
44 }
45 
46 int PlayerControl::get_cnt() {
47     return total_cnt;
48 }

task3.cpp

 1 #include "PlayerControl.h"
 2 #include <iostream>
 3 
 4 void test() {
 5     PlayerControl controller;
 6     std::string control_str;
 7     std::cout << "Enter Control: (play/pause/next/prev/stop/quit):\n";
 8 
 9     while(std::cin >> control_str) {
10         if(control_str == "quit")
11             break;
12         
13         ControlType cmd = controller.parse(control_str);
14         controller.execute(cmd);
15         std::cout << "Current Player control: " << PlayerControl::get_cnt() << "\n\n";
16     }
17 }
18 
19 int main() {
20     test();
21 }

运行结果截图：屏幕截图 2025-10-28 202056

 

4.实验任务4

Fraction.h

 1 #pragma once
 2 
 3 #include <iostream>
 4 #include <string>
 5 
 6 class Fraction{
 7     public:
 8         Fraction(int u = 0, int d = 1);
 9         Fraction(const Fraction &f);
10         
11         int get_up() const;
12         int get_down() const;
13         Fraction negative() ;
14         
15     private:
16         int up, down; 
17         
18     public:
19         static const std::string doc;
20         
21     friend void output(const Fraction &f);
22     friend Fraction add(const Fraction &f1, const Fraction &f2);
23     friend Fraction sub(const Fraction &f1, const Fraction &f2);
24     friend Fraction mul(const Fraction &f1, const Fraction &f2);
25     friend Fraction div(const Fraction &f1, const Fraction &f2);
26 };
27 
28     void output(const Fraction &f);
29     Fraction add(const Fraction &f1, const Fraction &f2);
30     Fraction sub(const Fraction &f1, const Fraction &f2);
31     Fraction mul(const Fraction &f1, const Fraction &f2);
32     Fraction div(const Fraction &f1, const Fraction &f2);

Fraction.cpp

 1 #include "Fraction.h"
 2 
 3 #include <iostream>
 4 #include <string>
 5 #include <cstdlib>
 6 
 7 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."};
 8 
 9 Fraction::Fraction(int u, int d ):up(u),down(d){} 
10         
11 Fraction::Fraction(const Fraction &f):up(f.get_up()),down(f.get_down()){}
12 
13 int Fraction::get_up() const {
14     return up;
15 }
16 
17 
18 int Fraction::get_down() const {
19     return down;
20 }
21 
22 
23 Fraction Fraction::negative() {
24     
25     int u = abs(up),  d = abs(down), t;
26     while(d!=0){
27         t = d;
28         d = u%d;
29         u = t;
30     }
31     
32     if(up*down < 0)
33         up = -abs(up)/u, down = abs(down)/u;
34     else
35         up = abs(up)/u, down = abs(down)/u;
36     const Fraction f(-get_up(), get_down());
37     return f;
38 }
39 
40 
41 void output(const Fraction &f){
42     
43     int u = abs(f.up),  d = abs(f.down), t;
44     while(d!=0){
45         t = d;
46         d = u%d;
47         u = t;
48     }
49     
50     
51             
52     if(f.get_down() == 0)
53         std::cout << "分母不能为0";
54             
55     else if(abs(f.get_up())%abs(f.get_down()) == 0)
56         std::cout << f.get_up()/u ;
57         
58     else if(f.get_up()*f.get_down() < 0)
59         std::cout << -abs(f.get_up()/u)<< "/" << abs(f.get_down()/u);
60         
61     else
62         std::cout << abs(f.get_up()/u) << "/" << abs(f.get_down()/u);
63 }
64 
65 
66 Fraction add(const Fraction &f1, const Fraction &f2){
67     Fraction f(f1.get_up()*f2.get_down()+f2.get_up()*f1.get_down(), f1.get_down()*f2.get_down());
68     return f;
69 }
70 
71 
72 Fraction sub(const Fraction &f1, const Fraction &f2){
73     Fraction f(f1.get_up()*f2.get_down()-f2.get_up()*f1.get_down(), f1.get_down()*f2.get_down());
74     return f;
75 }
76 
77 
78 Fraction mul(const Fraction &f1, const Fraction &f2){
79     Fraction f(f1.get_up()*f2.get_up(), f1.get_down()*f2.get_down());
80     return f;
81 }
82 
83 
84 Fraction div(const Fraction &f1, const Fraction &f2){
85     Fraction f(f1.get_up()*f2.get_down(), f1.get_down()*f2.get_up());
86     return f;
87 }

task4.cpp

 1 #include "Fraction.h"
 2 #include <iostream>
 3 
 4 void test1();
 5 void test2();
 6 
 7 int main() {
 8     std::cout << "测试1: Fraction类基础功能测试\n";
 9     test1();
10 
11     std::cout << "\n测试2: 分母为0测试: \n";
12     test2();
13 }
14 
15 void test1() {
16     using std::cout;
17     using std::endl;   
18 
19     cout << "Fraction类测试: " << endl;
20     cout << Fraction::doc << endl << endl;
21 
22     Fraction f1(5);
23     Fraction f2(3, -4), f3(-18, 12);
24     Fraction f4(f3);
25     cout << "f1 = "; output(f1); cout << endl;
26     cout << "f2 = "; output(f2); cout << endl;
27     cout << "f3 = "; output(f3); cout << endl;
28     cout << "f4 = "; output(f4); cout << endl;
29 
30     const Fraction f5(f4.negative());
31     cout << "f5 = "; output(f5); cout << endl;
32     cout << "f5.get_up() = " << f5.get_up() 
33         << ", f5.get_down() = " << f5.get_down() << endl;
34 
35     cout << "f1 + f2 = "; output(add(f1, f2)); cout << endl;
36     cout << "f1 - f2 = "; output(sub(f1, f2)); cout << endl;
37     cout << "f1 * f2 = "; output(mul(f1, f2)); cout << endl;
38     cout << "f1 / f2 = "; output(div(f1, f2)); cout << endl;
39     cout << "f4 + f5 = "; output(add(f4, f5)); cout << endl;
40 }
41 
42 void test2() {
43     using std::cout;
44     using std::endl;
45 
46     Fraction f6(42, 55), f7(0, 3);
47     cout << "f6 = "; output(f6); cout << endl;
48     cout << "f7 = "; output(f7); cout << endl;
49     cout << "f6 / f7 = "; output(div(f6, f7)); cout << endl;
50 }

运行结果截图：image

问题：友元函数，优点是增强灵活性与便利性，提高效率；缺点是破坏封装性。

posted @ 2025-10-28 21:07  gher  阅读(6)  评论(1)    收藏  举报