实验2 类和对象_基础编程1

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 // 类T: 实现
 2 // 普通函数实现
 3 
 4 #include "t.h"
 5 #include <iostream>
 6 #include <string>
 7 
 8 using std::cout;
 9 using std::endl;
10 using std::string;
11 
12 // static成员数据类外初始化
13 const std::string T::doc{"a simple class sample"};
14 const int T::max_cnt = 999;
15 int T::cnt = 0;
16 
17 
18 // 对象方法
19 T::T(int x, int y): m1{x}, m2{y} { 
20     ++cnt; 
21     cout << "T constructor called.\n";
22 } 
23 
24 T::T(const T &t): m1{t.m1}, m2{t.m2} {
25     ++cnt;
26     cout << "T copy constructor called.\n";
27 }
28 
29 T::T(T &&t): m1{t.m1}, m2{t.m2} {
30     ++cnt;
31     cout << "T move constructor called.\n";
32 }    
33 
34 T::~T() {
35     --cnt;
36     cout << "T destructor called.\n";
37 }           
38 
39 void T::adjust(int ratio) {
40     m1 *= ratio;
41     m2 *= ratio;
42 }    
43 
44 void T::display() const {
45     cout << "(" << m1 << ", " << m2 << ")" ;
46 }     
47 
48 // 类方法
49 int T::get_cnt() {
50    return cnt;
51 }
52 
53 // 友元
54 void func() {
55     T t5(42);
56     t5.m2 = 2049;
57     cout << "t5 = "; t5.display(); cout << endl;
58 }

task1.cpp

 1 #include "t.h"
 2 #include <iostream>
 3 
 4 using std::cout;
 5 using std::endl;
 6 
 7 void test();
 8 
 9 int main() {
10     test();
11     cout << "\nmain: \n";
12     cout << "T objects'current count: " << T::get_cnt() << endl;
13 }
14 
15 void test() {
16     cout << "test class T: \n";
17     cout << "T info: " << T::doc << endl;
18     cout << "T objects'max count: " << T::max_cnt << endl;
19     cout << "T objects'current count: " << T::get_cnt() << endl << endl;
20 
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 << "t3 = "; t4.display(); cout << endl;
34 
35     cout << "T objects'current count: " << T::get_cnt() << endl;
36 
37     func();
38 }

运行测试结果截图

问题1

t.h中，普通函数 func 作为类X的友元，在类的内部声明了友元关系。在类外部，去掉line36，重

新编译,编译器报错，报错信息如下：

可能的原因：当只在类内部声明友元函数时，编译器无法找到函数的声明，必须在类外部声明。

问题2

t.h中，line9-12给出了各种构造函数、析构函数，总结功能及调用时机。

line9：普通构造函数（带参数）功能：在对象被创建时利用特定值构造对象，将对象初始化为一个特定的状态（传递参数或使用默认参数）。调用时机：对象被创建时。

line10：复制构造函数功能：使用一个已经存在的对象（由复制构造函数参数&t决定），去初始化同类的一个新对象。调用时机：当一个对象以另一个对象为初始化参数进行初始化时。

line11：移动构造函数功能：将已有对象的值移动给同类的一个新对象。调用时机：当临时对象用于初始化新对象时。

line12：析构函数功能：清理对象占用的资源。调用时机：对象的生存期即将结束时（对象作用域结束）。

问题3

t.cpp中，line13-15，调整到t.h，重新编译，程序能正确编译运行。说明static成员数据可以在头文件中（类外）初始化。

任务2：

Complex.h

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

Complex.cpp

  1 #include "x.h"
  2 #include <iostream>
  3 #include <cmath>
  4 #include <string>
  5 
  6 Complex::Complex() : real(0), imag(0) {}
  7 Complex::Complex(double r) : real(r), imag(0) {}
  8 Complex::Complex(double r, double i) : real(r), imag(i) {}
  9 Complex::Complex(const Complex& other) : real(other.real), imag(other.imag) {}
 10 Complex::~ Complex() {}
 11 
 12 double Complex::get_real() const {
 13     return real;
 14 }
 15 
 16 double Complex::get_imag() const {
 17     return imag;
 18 }
 19 
 20 void Complex::add(const Complex& other) {
 21     real += other.get_real();
 22     imag += other.get_imag();
 23 }
 24 
 25 Complex add(const Complex& c1, const Complex& c2) {
 26     return Complex(c1.real + c2.real, c1.imag + c2.imag);
 27 }
 28 
 29 bool is_equal(const Complex& c1, const Complex& c2) {
 30     return (c1.real == c2.real) && (c1.imag == c2.imag);
 31 }
 32 
 33 bool is_not_equal(const Complex& c1, const Complex& c2) {
 34     return !is_equal(c1, c2);
 35 }
 36 
 37 void output(const Complex& c) {
 38     std::cout << c.get_real() << (c.get_imag() >= 0 ? " + " : " - ") << std::fabs(c.get_imag()) << "i";
 39 }
 40 
 41 double abs(const Complex& c) {
 42     return std::sqrt(c.real * c.real + c.imag * c.imag);
 43 }
 44 
 45 const std::string Complex::doc {"a simplified complex class"};#include "x.h"
 46 #include <iostream>
 47 #include <cmath>
 48 #include <string>
 49 
 50 Complex::Complex() : real(0), imag(0) {}
 51 Complex::Complex(double r) : real(r), imag(0) {}
 52 Complex::Complex(double r, double i) : real(r), imag(i) {}
 53 Complex::Complex(const Complex& other) : real(other.real), imag(other.imag) {}
 54 Complex::~ Complex() {}
 55 
 56 double Complex::get_real() const {
 57     return real;
 58 }
 59 
 60 double Complex::get_imag() const {
 61     return imag;
 62 }
 63 
 64 void Complex::add(const Complex& other) {
 65     real += other.get_real();
 66     imag += other.get_imag();
 67 }
 68 
 69 Complex add(const Complex& c1, const Complex& c2) {
 70     return Complex(c1.real + c2.real, c1.imag + c2.imag);
 71 }
 72 
 73 bool is_equal(const Complex& c1, const Complex& c2) {
 74     return (c1.real == c2.real) && (c1.imag == c2.imag);
 75 }
 76 
 77 bool is_not_equal(const Complex& c1, const Complex& c2) {
 78     return !is_equal(c1, c2);
 79 }
 80 
 81 void output(const Complex& c) {
 82     std::cout << c.get_real() << (c.get_imag() >= 0 ? " + " : " - ") << std::fabs(c.get_imag()) << "i";
 83 }
 84 
 85 double abs(const Complex& c) {
 86     return std::sqrt(c.real * c.real + c.imag * c.imag);
 87 }
 88 
 89 const std::string Complex::doc {"a simplified complex class"};#include "x.h"
 90 #include <iostream>
 91 #include <cmath>
 92 #include <string>
 93 
 94 Complex::Complex() : real(0), imag(0) {}
 95 Complex::Complex(double r) : real(r), imag(0) {}
 96 Complex::Complex(double r, double i) : real(r), imag(i) {}
 97 Complex::Complex(const Complex& other) : real(other.real), imag(other.imag) {}
 98 Complex::~ Complex() {}
 99 
100 double Complex::get_real() const {
101     return real;
102 }
103 
104 double Complex::get_imag() const {
105     return imag;
106 }
107 
108 void Complex::add(const Complex& other) {
109     real += other.get_real();
110     imag += other.get_imag();
111 }
112 
113 Complex add(const Complex& c1, const Complex& c2) {
114     return Complex(c1.real + c2.real, c1.imag + c2.imag);
115 }
116 
117 bool is_equal(const Complex& c1, const Complex& c2) {
118     return (c1.real == c2.real) && (c1.imag == c2.imag);
119 }
120 
121 bool is_not_equal(const Complex& c1, const Complex& c2) {
122     return !is_equal(c1, c2);
123 }
124 
125 void output(const Complex& c) {
126     std::cout << c.get_real() << (c.get_imag() >= 0 ? " + " : " - ") << std::fabs(c.get_imag()) << "i";
127 }
128 
129 double abs(const Complex& c) {
130     return std::sqrt(c.real * c.real + c.imag * c.imag);
131 }
132 
133 const std::string Complex::doc {"a simplified complex class"};

task2.cpp

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

运行测试结果截图

总结

1.注意string在namespace标准库中，用std::访问。

2.static成员数据在类外进行初始化。

3.适当使用const保护数据。

任务3：

task3.cpp

 1 #include <iostream>
 2 #include <complex>
 3 
 4 using std::cout;
 5 using std::endl;
 6 using std::boolalpha;
 7 using std::complex;
 8 
 9 void test() {
10     cout << "标准库模板类comple测试: " << endl;
11     complex<double> c1;
12     complex<double> c2(3, -4);
13     const complex<double> c3(3.5);
14     complex<double> c4(c3);
15 
16     cout << "c1 = " << c1 << endl;
17     cout << "c2 = " << c2 << endl;
18     cout << "c3 = " << c3 << endl;
19     cout << "c4 = " << c4 << endl;
20     cout << "c4.real = " << c4.real() << ", c4.imag = " << c4.imag() << endl;
21     cout << endl;
22 
23     cout << "复数运算测试: " << endl;
24     cout << "abs(c2) = " << abs(c2) << endl;
25     c1 += c2;
26     cout << "c1 += c2, c1 = " << c1 << endl;
27     cout << boolalpha;
28     cout << "c1 == c2 : " << (c1 == c2) << endl;
29     cout << "c1 != c3 : " << (c1 != c3) << endl;
30     c4 = c2 + c3;
31     cout << "c4 = c2 + c3, c4 = " << c4 << endl;
32 }
33 
34 int main() {
35     test();
36 }

运行测试结果截图

总结

1.注意标准模板类complex在namespace标准库中，用std::访问。

2.模板类complex可以直接通过.real() .imag()分别返回对象的实部和虚部；直接通过“+” “-”进行复数的加法减法运算；abs()为求模运算；直接通过“==”判等

3.复数作为常见的一种数，通过直接使用模板类complex可以无需自己定义复数类使用较方便。

任务4：

Fraction.h

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

Fraction.cpp

  1 #include "Fraction.h" 
  2 #include <iostream>
  3 #include <string>
  4 
  5 using std::cout;
  6 using std::endl;
  7 using std::string;
  8 
  9 const 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."};
 10 
 11 Fraction::Fraction(int u, int d): up{u}, down{d} {
 12 }
 13 
 14 Fraction::Fraction(const Fraction& other): up{other.up}, down{other.down} {}
 15 
 16 Fraction::~Fraction() {}
 17 
 18 int Fraction::get_up() const{
 19     int a = up, b = down; 
 20     int u = up, d = down;
 21     while (b != 0) {
 22         int temp = b;
 23         b = a % b;
 24         a = temp;
 25     }
 26     int gcd = a;
 27     u /= gcd;
 28     d /= gcd;
 29     if (d < 0) {
 30         d = -d;
 31         u = -u;
 32     }
 33     return u;
 34 } 
 35 
 36 int Fraction::get_down() const{
 37     int a = up, b = down; 
 38     int u = up, d = down;
 39     while (b != 0) {
 40         int temp = b;
 41         b = a % b;
 42         a = temp;
 43     }
 44     int gcd = a;
 45     u /= gcd;
 46     d /= gcd;
 47     if (d < 0) {
 48         d = -d;
 49         u = -u;
 50     }
 51     return d;
 52 } 
 53 
 54 Fraction Fraction::negative() const{
 55     return Fraction(-up, down);
 56 } 
 57 
 58 void output(const Fraction &f) {
 59     if(f.down == 0) {
 60         cout << "分母不能为0"; 
 61         return;
 62     }
 63 
 64     int a = f.up, b = f.down; 
 65     int u = f.up, d = f.down;
 66     while (b != 0) {
 67         int temp = b;
 68         b = a % b;
 69         a = temp;
 70     }
 71     int gcd = a;
 72     u /= gcd;
 73     d /= gcd;
 74     if (d < 0) {
 75         d = -d;
 76         u = -u;
 77     }
 78     if(u == 0)
 79         cout << 0;
 80     else if(d == 1)
 81         cout << u;
 82     else
 83         cout << u << "/" << d ;
 84 }
 85 
 86 Fraction add(const Fraction& f1, const Fraction& f2) {
 87     return Fraction(f1.up * f2.down + f2.up * f1.down, f1.down * f2.down);
 88 }
 89 
 90 Fraction sub(const Fraction& f1, const Fraction& f2) {
 91     return Fraction(f1.up * f2.down - f2.up * f1.down, f1.down * f2.down);
 92 }
 93 
 94 Fraction mul(const Fraction& f1, const Fraction& f2) {
 95     return Fraction(f1.up * f2.up, f1.down * f2.down);
 96 }
 97 
 98 Fraction div(const Fraction& f1, const Fraction& f2) {
 99     return Fraction(f1.up * f2.down, f1.down * f2.up);
100 }

task4.cpp

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

运行测试结果截图

总结

1.在设计友元函数output时出现了问题，查看报错信息发现友元函数只能访问类的私有成员，不能修改私有成员。于是重新设计代码，只在输出时输出最简分数，而不改变私有成员up,down的值使其最简。此外，在output函数中要首先判断分母是否等于0（分数是否合理）。

2.在接口get_up和get_down时也要返回化简后的分子和分母，同1。

任务5：

account.h

 1 #ifndef __ACCOUNT_H__
 2 #define __ACCOUNT_H__
 3 class SavingsAccount { //储蓄账户类
 4 private:
 5     int id;                //账号
 6     double balance;        //余额
 7     double rate;        //存款的年利率
 8     int lastDate;        //上次变更余额的时期
 9     double accumulation;    //余额按日累加之和
10     static double total;    //所有账户的总金额
11     //记录一笔帐，date为日期，amount为金额，desc为说明
12     void record(int date, double amount);
13     //获得到指定日期为止的存款金额按日累积值
14     double accumulate(int date) const {
15         return accumulation + balance * (date - lastDate);
16     }
17 public:
18     //构造函数
19     SavingsAccount(int date, int id, double rate);
20     int getId() const { return id; }
21     double getBalance() const { return balance; }
22     double getRate() const { return rate; }
23     static double getTotal() { return total; }
24     void deposit(int date, double amount);         //存入现金
25     void withdraw(int date, double amount);     //取出现金
26     //结算利息，每年1月1日调用一次该函数
27     void settle(int date);
28     //显示账户信息
29     void show() const;
30 };
31 #endif //__ACCOUNT_H__

account.cpp

 1 #include "account.h"
 2 #include <cmath>
 3 #include <iostream>
 4 using namespace std;
 5 
 6 double SavingsAccount::total = 0;
 7 //SavingsAccount类相关成员函数的实现 
 8 SavingsAccount::SavingsAccount(int date, int id, double rate)
 9         : id(id), balance(0), rate(rate), lastDate(date), accumulation(0) {
10     cout << date << "\t#" << id << " is created" << endl;
11 }
12 void SavingsAccount::record(int date, double amount) {
13     accumulation = accumulate(date);
14     lastDate = date;
15     amount = floor(amount * 100 + 0.5) / 100;    //保留小数点后两位 
16     balance += amount;
17     total += amount;
18     cout << date << "\t#" << id << "\t" << amount << "\t" << balance << endl;
19 }
20 void SavingsAccount::deposit(int date, double amount) {
21     record(date, amount);
22 }
23 void SavingsAccount::withdraw(int date, double amount) {
24     if (amount > getBalance())
25         cout << "Error: not enough money" << endl;
26     else
27         record(date, -amount);
28 }
29 void SavingsAccount::settle(int date) {
30     double interest = accumulate(date) * rate / 365;    //计算年息 
31     if (interest != 0)
32         record(date, interest);
33     accumulation = 0;
34 }
35 void SavingsAccount::show() const {
36     cout << "#" << id << "\tBalance: " << balance;
37 }

5_11.cpp

 1 #include "account.h"
 2 #include <iostream>
 3 using namespace std;
 4 int main() {
 5     //建立几个账户 
 6     SavingsAccount sa0(1, 21325302, 0.015);
 7     SavingsAccount sa1(1, 58320212, 0.015);
 8     //几笔账目 
 9     sa0.deposit(5, 5000);
10     sa1.deposit(25, 10000);
11     sa0.deposit(45, 5500);
12     sa1.withdraw(60, 4000);
13     //开户第90天到了银行的计息日，结算所有账户的年息 
14     sa0.settle(90);
15     sa1.settle(90);
16     //输出各个账户信息 
17     sa0.show();    cout << endl;
18     sa1.show();    cout << endl;
19     cout << "Total: " << SavingsAccount::getTotal() << endl;
20     return 0;
21 }

运行测试结果截图

分析

改进：1.此储蓄账户类的设计较第四章相比增加了部分const修饰成员函数，一定程度上增加了账户的安全性。2.增加了静态数据成员total记录账户总金额，使用户使用更便捷。

不足：1.此储蓄账户的安全性不足，主要体现在没有设计密码成员，导致查询余额等函数接口不安全。2.结息等操作数据精度不够。

posted @ 2024-10-22 19:04 吴婧希阅读(37) 评论(0) 收藏举报

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