实验二

1、实验任务1：

T.h源代码：

 1 #pragma once
 2 
 3 #include <string>
 4 
 5 class T {
 6     
 7 public:
 8     T(int x = 0, int y = 0);
 9     T(const T &t);
10     T(T &&t);
11     ~T(); 
12 
13     void adjust(int ratio); 
14     void display() const;
15 
16 private:
17     int m1, m2;
18 
19 public:
20     static int get_cnt();
21 
22 public:
23     static const std::string doc;
24     static const int max_cnt;
25 
26 private:
27     static int cnt;
28 
29     friend void func();
30 };
31 
32 void func();

T.cpp源代码：

 1 #include "T.h"
 2 #include <iostream>
 3 #include <string>
 4 
 5 const std::string T::doc{"a simple class sample"};
 6 const int T::max_cnt = 999;
 7 int T::cnt = 0;
 8 
 9 int T::get_cnt() {
10    return cnt;
11 }
12 
13 T::T(int x, int y): m1{x}, m2{y} { 
14     ++cnt; 
15     std::cout << "T constructor called.\n";
16 } 
17 
18 T::T(const T &t): m1{t.m1}, m2{t.m2} {
19     ++cnt;
20     std::cout << "T copy constructor called.\n";
21 }
22 
23 T::T(T &&t): m1{t.m1}, m2{t.m2} {
24     ++cnt;
25     std::cout << "T move constructor called.\n";
26 }    
27 
28 T::~T() {
29     --cnt;
30     std::cout << "T destructor called.\n";
31 }           
32 
33 void T::adjust(int ratio) {
34     m1 *= ratio;
35     m2 *= ratio;
36 }    
37 
38 void T::display() const {
39     std::cout << "(" << m1 << ", " << m2 << ")" ;
40 }     
41 
42 void func() {
43     T t5(42);
44     t5.m2 = 2049;
45     std::cout << "t5 = "; t5.display(); std::cout << '\n';
46 }

task1.cpp源代码：

 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 }

运行测试截图：

回答问题：

问题1：Yes

问题2：

普通构造函数：功能：创建新对象并初始化数据成员；创建新对象时
复制构造函数：功能：用已有对象创建新对象；对象拷贝时
移动构造函数：功能：转移资源所有权而不复制；使用右值引用时
析构函数：功能：清理对象资源，减少对象计数；对象生命周期结束时自动调用

问题3：能

2、实验任务2：

Complex.h源代码：

 1 #pragma once
 2 #include <string>
 3 
 4 class Complex {
 5 public:
 6     static const std::string doc;
 7 
 8     Complex(double real = 0.0, double imag = 0.0);
 9     Complex(const Complex &other);
10 
11     double get_real() const;
12     double get_imag() const;
13     void add(const Complex &other);
14 
15     friend void output(const Complex &c);
16     friend double abs(const Complex &c);
17     friend Complex add(const Complex &c1, const Complex &c2);
18     friend bool is_equal(const Complex &c1, const Complex &c2);
19     friend bool is_not_equal(const Complex &c1, const Complex &c2);
20 
21 private:
22     double real;
23     double imag;
24 };

Complex.cpp源代码：

 1 #include "Complex.h"
 2 #include <iostream>
 3 #include <cmath>
 4 
 5 const std::string Complex::doc = "a simplified Complex class";
 6 
 7 Complex::Complex(double real, double imag) : real(real), imag(imag) {}
 8 Complex::Complex(const Complex &other) : real(other.real), imag(other.imag) {}
 9 
10 double Complex::get_real() const { return real; }
11 double Complex::get_imag() const { return imag; }
12 void Complex::add(const Complex &other) {
13     real += other.real;
14     imag += other.imag;
15 }
16 
17 void output(const Complex &c) {
18     if (c.imag >= 0) {
19         std::cout << c.real << " + " << c.imag << "i";
20     } else {
21         std::cout << c.real << " - " << -c.imag << "i";
22     }
23 }
24 
25 double abs(const Complex &c) {
26     return std::sqrt(c.real * c.real + c.imag * c.imag);
27 }
28 
29 Complex add(const Complex &c1, const Complex &c2) {
30     return Complex(c1.real + c2.real, c1.imag + c2.imag);
31 }
32 
33 bool is_equal(const Complex &c1, const Complex &c2) {
34     return c1.real == c2.real && c1.imag == c2.imag;
35 }
36 
37 bool is_not_equal(const Complex &c1, const Complex &c2) {
38     return !is_equal(c1, c2);
39 }

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 namespace std;
19     cout << "类成员测试：\n";
20     cout << Complex::doc << "\n\n";
21 
22     cout << "Complex对象测试：\n";
23     Complex c1;
24     Complex c2(3, -4);
25     Complex c3(c2);
26     Complex c4 = c2;
27     const Complex c5(3.5);
28 
29     cout << "c1 = "; output(c1); cout << "\n";
30     cout << "c2 = "; output(c2); cout << "\n";
31     cout << "c3 = "; output(c3); cout << "\n";
32     cout << "c4 = "; output(c4); cout << "\n";
33     cout << "c5.real = " << c5.get_real() 
34          << ", c5.imag = " << c5.get_imag() << "\n\n";
35 
36     cout << "复数运算测试：\n";
37     cout << "abs(c2) = " << abs(c2) << "\n";
38     c1.add(c2);
39     cout << "c1 += c2, c1 = "; output(c1); cout << "\n";
40     cout << boolalpha;
41     cout << "c1 == c2 : " << is_equal(c1, c2) << "\n";
42     cout << "c1 != c2 : " << is_not_equal(c1, c2) << "\n";
43     Complex c6 = add(c2, c3);
44     cout << "c4 = c2 + c3, c4 = "; output(c6); cout << "\n";
45 }
46 
47 void test_std_complex() {
48     using namespace std;
49     cout << "std::complex<double>对象测试：\n";
50     complex<double> c1;
51     complex<double> c2(3, -4);
52     complex<double> c3(c2);
53     complex<double> c4 = c2;
54     const complex<double> c5(3.5);
55 
56     cout << "c1 = " << c1 << "\n";
57     cout << "c2 = " << c2 << "\n";
58     cout << "c3 = " << c3 << "\n";
59     cout << "c4 = " << c4 << "\n";
60     cout << "c5.real = " << c5.real() 
61          << ", c5.imag = " << c5.imag() << "\n\n";
62 
63     cout << "复数运算测试：\n";
64     cout << "abs(c2) = " << abs(c2) << "\n";
65     c1 += c2;
66     cout << "c1 += c2, c1 = " << c1 << "\n";
67     cout << boolalpha;
68     cout << "c1 == c2 : " << (c1 == c2) << "\n";
69     cout << "c1 != c2 : " << (c1 != c2) << "\n";
70     complex<double> c6 = c2 + c3;
71     cout << "c4 = c2 + c3, c4 = " << c6 << "\n";
72 }

运行代码截图：

回答问题：

问题1：标准库模板类complex更简洁；函数和运算逻辑关联一致，都是实部加实部、虚部加虚部，取模都是计算模长

问题2：

2-1：是。output需要访问实部和虚部来格式化输出；abs需要实部和虚部计算模长；add需要访问两个复数的实部和虚部来做加法

2-2：否。标准库std::complex的abs是通过公共接口real()和imag()获取实部、虚部后计算的，未将abs设为友元

2-3：当外部函数需要访问当前类的私有成员

问题3：删除复制构造函数

3、实验任务3：

PlayerControl.cpp源代码：

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

PlayerControl.h源代码：

 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);
11     void execute(ControlType cmd) const;     
12 
13     static int get_cnt();
14 
15 private:
16     static int total_cnt;   
17 };

task3.cpp源代码：

 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 }

运行代码截图：

4、实验任务4：

Fraction.h源代码：

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

Fraction.cpp源代码：

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

task4.cpp源代码：

 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 }

运行代码截图：

回答问题：选择友元函数方案

理由：优点：可直接访问Fraction类的私有成员，无需通过公共接口间接获取，简化分数运算的实现逻辑；缺点：一定程度上破坏了类的分装性

posted @ 2025-10-28 22:56 雅ya 阅读(6) 评论(1) 收藏举报

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实验二

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