实验5 继承和多态 - Forgiver

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实验任务3

代码：

pets.hpp

 1 #pragma once
 2 #include <iostream>
 3 
 4 using namespace std;
 5 
 6 class MachinePets {
 7 public:
 8     MachinePets(const string& s);
 9     string get_nickname() const;
10     virtual string talk() = 0;
11 
12 private:
13     string nickname;
14 };
15 
16 class PetCats : public MachinePets {
17 public:
18     PetCats(const string& s);
19     string talk();
20 };
21 
22 class PetDogs : public MachinePets {
23 public:
24     PetDogs(const string& s);
25     string talk();
26 };
27 
28 MachinePets::MachinePets(const string& s) : nickname{ s } {}
29 
30 string MachinePets::get_nickname() const {
31     return nickname;
32 }
33 
34 PetCats::PetCats(const string& s) : MachinePets{ s } {}
35 
36 PetDogs::PetDogs(const string& s) : MachinePets{ s } {}
37 
38 string PetCats::talk() {
39     return "miao wu~";
40 }
41 
42 string PetDogs::talk() {
43     return "wang wang~";
44 }

task3.cpp

 1 #include <iostream>
 2 #include <vector>
 3 #include "pets.hpp"
 4 
 5 void test() {
 6     using namespace std;
 7 
 8     vector<MachinePets *> pets;
 9 
10     pets.push_back(new PetCats("miku"));
11     pets.push_back(new PetDogs("da huang"));
12 
13     for(auto &ptr: pets)
14         cout <<ptr->get_nickname() << " says " << ptr->talk() << endl;
15 }
16 
17 int main() {
18     test();
19 }

运行测试截图：

实验任务4

代码：

film.hpp

 1 #pragma once
 2 #include <iostream>
 3 #include <iomanip>
 4 
 5 using namespace std;
 6 
 7 class Film {
 8 public:
 9     Film();
10 
11     int getyear() const;
12 
13     friend istream& operator>>(istream& in, Film& f);
14     friend ostream& operator<<(ostream& out, const Film& f);
15 
16 private:
17     string name;
18     string director;
19     string nation;
20     int year;
21 };
22 
23 Film::Film() {}
24 
25 int Film::getyear() const {
26     return year;
27 }
28 
29 istream& operator>>(istream& in, Film& f) {
30     cout << "录入片名："; in >> f.name;
31     cout << "录入导演："; in >> f.director;
32     cout << "录入制片国家/地区："; in >> f.nation;
33     cout << "录入上映年份："; in >> f.year;
34 
35     return in;
36 }
37 
38 ostream& operator<<(ostream& out, const Film& f) {
39     out << left;
40     out << setw(15) << f.name
41         << setw(20) << f.director
42         << setw(15) << f.nation
43         << setw(15) << f.year;
44 
45     return out;
46 }
47 
48 
49 bool compare_by_year(const Film& f1, const Film& f2) {
50     return f1.getyear() > f2.getyear();
51 }

task4.cpp

 1 #include "film.hpp"
 2 #include <iostream>
 3 #include <string>
 4 #include <vector>
 5 #include <algorithm>
 6 
 7 void test() {
 8     using namespace std;
 9     
10     int n;
11     cout << "输入电影数目: ";
12     cin >> n;
13 
14     cout << "录入" << n << "部影片信息" << endl;
15     vector<Film> film_lst;
16     for(int i = 0; i < n; ++i) {
17         Film f;
18         cout << string(20, '-') << "第" << i+1 << "部影片录入" << string(20, '-') << endl;
19         cin >> f;
20         film_lst.push_back(f);
21     }
22 
23     // 按发行年份升序排序
24     sort(film_lst.begin(), film_lst.end(), compare_by_year);
25 
26     cout << string(20, '=') + "电影信息(按发行年份)" +  string(20, '=')<< endl;
27     for(auto &f: film_lst)
28         cout << f << endl;
29 }
30 
31 int main() {
32     test();
33 }

运行测试截图：

实验任务5

代码：

Complex.hpp

 1 #pragma once
 2 #include <iostream>
 3 
 4 using namespace std;
 5 
 6 template <typename T>
 7 class Complex {
 8 public:
 9     Complex(T r = 0, T i = 0);
10     Complex(const Complex& c);
11     T get_real() const;
12     T get_imag() const;
13     Complex operator+=(const Complex& c);
14     bool operator==(const Complex& c);
15 
16     template <typename T> friend Complex<T> operator+(const Complex<T>& c1, const Complex<T>& c2);
17     template <typename T> friend istream& operator>>(istream& in, Complex<T>& c);
18     template <typename T> friend ostream& operator<<(ostream& out, const Complex<T>& c);
19 
20 private:
21     T real, imag;
22 };
23 
24 template <typename T>
25 Complex<T>::Complex(T r, T i) : real{ r }, imag{ i } {}
26 
27 template <typename T>
28 Complex<T>::Complex(const Complex& c) : real{ c.real }, imag{c.imag} {}
29 
30 template <typename T>
31 T Complex<T>::get_real() const { return real; }
32 
33 template <typename T>
34 T Complex<T>::get_imag() const { return imag; }
35 
36 template <typename T>
37 Complex<T> Complex<T>::operator+=(const Complex& c) {
38     real += c.real;
39     imag += c.imag;
40 
41     return *this;
42 }
43 
44 template <typename T>
45 bool Complex<T>::operator==(const Complex& c) {
46     if (real == c.real && imag == c.imag)
47         return true;
48     else return false;
49 }
50 
51 template <typename T>
52 Complex<T> operator+(const Complex<T>& c1, const Complex<T>& c2) {
53     return Complex<T>(c1.real + c2.real, c1.imag + c2.imag);
54 }
55 
56 
57 template <typename T>
58 istream& operator>>(istream& in, Complex<T>& c) {
59     in >> c.real >> c.imag;
60 
61     return in;
62 }
63 
64 template <typename T>
65 ostream& operator<<(ostream& out, const Complex<T>& c) {
66     if (c.imag >= 0)
67         out << c.real << " + " << c.imag << "i";
68     else
69         out << c.real << " - " << -c.imag << "i";
70 
71     return out;
72 }

task5.cpp

 1 #include "Complex.hpp"
 2 #include <iostream>
 3 
 4 using std::cin;
 5 using std::cout;
 6 using std::endl;
 7 using std::boolalpha;
 8 
 9 void test1() {
10     Complex<int> c1(2, -5), c2(c1);
11 
12     cout << "c1 = " << c1 << endl;
13     cout << "c2 = " << c2 << endl;
14     cout << "c1 + c2 = " << c1 + c2 << endl;
15     
16     c1 += c2;
17     cout << "c1 = " << c1 << endl;
18     cout << boolalpha << (c1 == c2) << endl;
19 }
20 
21 void test2() {
22     Complex<double> c1, c2;
23     cout << "Enter c1 and c2: ";
24     cin >> c1 >> c2;
25     cout << "c1 = " << c1 << endl;
26     cout << "c2 = " << c2 << endl;
27 
28     cout << "c1.real = " << c1.get_real() << endl;
29     cout << "c1.imag = " << c1.get_imag() << endl;
30 }
31 
32 int main() {
33     cout << "自定义类模板Complex测试1: " << endl;
34     test1();
35 
36     cout << endl;
37 
38     cout << "自定义类模板Complex测试2: " << endl;
39     test2();
40 }

运行测试截图（）

实验任务6

代码：

date.h

 1 #pragma once
 2 
 3 class Date {
 4 private:
 5     int year;
 6     int month;
 7     int day;
 8     int totalDays;
 9 
10 public:
11     Date(int year, int month, int day);
12     int getYear() const { return year; }
13     int getMonth() const { return month; }
14     int getDay() const { return day; }
15     int getMaxDay() const;  //获得当月有多少天
16     bool isLeapYear() const {
17         return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
18     }
19     void show() const;
20     int operator-(const Date& date) const {
21         return totalDays - date.totalDays;
22     }
23 };

date.cpp

 1 #include "date.h"
 2 #include <iostream>
 3 #include <cstdlib>
 4 
 5 using namespace std;
 6 
 7 namespace {
 8     const int DAYS_BEFORE_MONTH[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
 9 }
10 
11 int Date::getMaxDay() const {
12     if (isLeapYear() && month == 2)
13         return 29;
14     else
15         return DAYS_BEFORE_MONTH[month] - DAYS_BEFORE_MONTH[month - 1];
16 }
17 
18 void Date::show() const {
19     cout << getYear() << "-" << getMonth() << "-" << getDay();
20 }
21 
22 Date::Date(int year, int month, int day) : year{ year }, month{ month }, day{ day } {
23     if (day <= 0 || day > getMaxDay()) {
24         cout << "Invalid date: ";
25         show();
26         cout << endl;
27         exit(1);
28     }
29     int years = year - 1;
30     totalDays = years * 365 + years / 4 - years / 100 + years / 400
31         + DAYS_BEFORE_MONTH[month - 1] + day;
32     if (isLeapYear() && month > 2) totalDays++;
33 }

accumulator.h

 1 #pragma once
 2 #include "date.h"
 3 
 4 class Accumulator {
 5 private:
 6     Date lastDate;  //上次变更数值的日期
 7     double value;
 8     double sum;
 9 
10 public:
11     Accumulator(const Date& date, double value)
12         :lastDate{date}, value{value}, sum{0}{}
13 
14     double getSum(const Date& date) const {
15         return sum + value * (date - lastDate);
16     }
17 
18     void change(const Date& date, double value) {
19         sum = getSum(date);
20         lastDate = date;
21         this->value = value;
22     }
23 
24     void reset(const Date& date, double value) {
25         lastDate = date;
26         this->value = value;
27         sum = 0;
28     }
29 
30 };

account.h

 1 #pragma once
 2 #include "date.h"
 3 #include "Accumulator.h"
 4 #include <string>
 5 
 6 class Account {  //账户类
 7 private:
 8     std::string id;  //账号
 9     double balance;  //余额
10     static double total;  //所有账户的总金额
11 
12 protected:
13     Account(const Date& date, const std::string& id);  //构造函数
14     void record(const Date& date, double amount, const std::string& desc);  //记账
15     void error(const std::string& msg) const;  //报告错误信息
16 
17 public:
18     const std::string& getId() const { return id; }
19     double getBalance() const { return balance; }
20     static double getTotal() { return total; }
21     
22     virtual void deposit(const Date& date, double amount, const std::string& desc) = 0;  //存入现金
23     virtual void withdraw(const Date& date, double amount, const std::string& desc) = 0;  //取出现金
24     virtual void settle(const Date& date) = 0;  //结算（利息、年费）
25     virtual void show() const;  //显示账户信息
26 };
27 
28 class SavingsAccount : public Account {  //储蓄类账户
29 private:
30     Accumulator acc;  //辅助计算利息的累加器
31     double rate;  //存款的年利率
32 
33 public:
34     SavingsAccount(const Date& date, const std::string& id, double rate);  //构造函数
35     double getRate() const { return rate; }
36     void deposit(const Date& date, double amount, const std::string& desc);  //存入现金
37     void withdraw(const Date& date, double amount, const std::string& desc);  //取出现金
38     void settle(const Date& date);  //结算利息
39 };
40 
41 class CreditAccount : public Account {  //信用账户类
42 private:
43     Accumulator acc;  //辅助计算利息的累加器
44     double credit;  //信用额度
45     double rate;  //欠款的日利率
46     double fee;  //信用卡年费
47     double getDebt() const {  //获得欠款额
48         double balance = getBalance();
49         return (balance < 0 ? balance : 0);
50     }
51 public:
52     CreditAccount(const Date& date, const std::string& id, double credit, double rate, double fee);
53     double getCredit() const { return credit; }
54     double getRate() const { return rate; }
55     double getFee() const { return fee; }
56     double getAvailableCredit() const {  //获得可用信用
57         if (getBalance() < 0)
58             return credit + getBalance();
59         else
60             return credit;
61     }
62     void deposit(const Date& date, double amount, const std::string& desc);  //存入现金
63     void withdraw(const Date& date, double amount, const std::string& desc);  //取出现金
64     void settle(const Date& date);  //结算利息
65     void show() const;
66 };

account.cpp

 1 #include "account.h"
 2 #include <cmath>
 3 #include <iostream>
 4 
 5 using namespace std;
 6 
 7 //Account类的实现
 8 double Account::total = 0;
 9 
10 Account::Account(const Date& date, const std::string& id)
11     : id{ id }, balance{ 0 } {
12     date.show();
13     cout << "\t#" << id << "created" << endl;
14 }
15 
16 void Account::record(const Date& date, double amount, const string& desc) {
17     amount = floor(amount * 100 + 0.5) / 100;
18     balance += amount;
19     total += amount;
20     date.show();
21     cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl;
22 }
23 
24 void Account::show() const {
25     cout << id << "\tBalance:" << balance;
26 }
27 
28 void Account::error(const string& msg) const {
29     cout << "Error(#" << id << "):" << msg << endl;
30 }
31 
32 
33 //SavingsAccount类的实现
34 SavingsAccount::SavingsAccount(const Date& date, const std::string& id, double rate)
35     : Account{ date, id }, rate{ rate }, acc{date, 0} {}
36 
37 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) {
38     record(date, amount, desc);
39     acc.change(date, getBalance());
40 }
41 
42 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) {
43     if (amount > getBalance())
44         error("not enough money");
45     else {
46         record(date, -amount, desc);
47         acc.change(date, getBalance());
48     }
49 }
50 
51 void SavingsAccount::settle(const Date& date) {
52     if (date.getMonth() == 1) {
53         double interest = acc.getSum(date) * rate  //计算年息
54             / (date - Date(date.getYear() - 1, 1, 1));
55         if (interest != 0)
56             record(date, interest, "interest");
57         acc.reset(date, getBalance());
58     }
59 }
60 
61 //CreditAccount类的实现
62 CreditAccount::CreditAccount(const Date& date, const std::string& id, double credit, double rate, double fee)
63     : Account{ date, id }, credit{ credit }, rate{ rate }, fee{fee}, acc{ date, 0 } {}
64 
65 void CreditAccount::deposit(const Date& date, double amount, const string& desc) {
66     record(date, amount, desc);
67     acc.change(date, getDebt());
68 }
69 
70 void CreditAccount::withdraw(const Date& date, double amount, const string& desc) {
71     if (amount - getBalance() > credit)
72         error("not enough credit");
73     else {
74         record(date, -amount, desc);
75         acc.change(date, getDebt());
76     }
77 }
78 
79 void CreditAccount::settle(const Date& date) {
80     double interest = acc.getSum(date) * rate;
81     if (interest != 0)
82         record(date, interest, "interest");
83     if (date.getMonth() == 1)
84         record(date, -fee, "annual fee");
85     acc.reset(date, getDebt());
86 }
87 
88 void CreditAccount::show() const{
89     Account::show();
90     cout << "\tAvailable credit:" << getAvailableCredit();
91 }

8_8.cpp

 1 #include "account.h"
 2 #include <iostream>
 3 
 4 using namespace std;
 5 
 6 int main() {
 7     Date date{ 2008, 11, 1 };
 8     SavingsAccount sa1{date, "S3755217", 0.015};
 9     SavingsAccount sa2{date, "02342342", 0.015};
10     CreditAccount ca{ date, "C5392394", 10000, 0.0005, 50 };
11 
12     Account* accounts[] = { &sa1, &sa2, &ca };
13     const int n = sizeof(accounts) / sizeof(Account*);
14 
15     cout << "(d)deposit (w)withdraw (s)show (c)change day (n)next month (e)exit" << endl;
16     char cmd;
17     do {
18         date.show();
19         cout << "\tTotal:" << Account::getTotal() << "\tcommand>";
20 
21         int index, day;
22         double amount;
23         string desc;
24         cin >> cmd;
25 
26         switch (cmd) {
27         case'd':  //存入现金
28             cin >> index >> amount;
29             getline(cin, desc);
30             accounts[index]->deposit(date, amount, desc);
31             break;
32 
33         case'w':  //取出现金
34             cin >> index >> amount;
35             getline(cin, desc);
36             accounts[index]->withdraw(date, amount, desc);
37             break;
38 
39         case's':  //查询各账户信息
40             for (int i = 0; i < n; i++) {
41                 cout << "[" << i << "]";
42                 accounts[i]->show();
43                 cout << endl;
44             }
45             break;
46 
47         case'c':  //改变日期
48             cin >> day;
49             if (day < date.getDay())
50                 cout << "You cannot specify a previous day";
51             else if (day > date.getMaxDay())
52                 cout << "Invalid day";
53             else
54                 date = Date(date.getYear(), date.getMonth(), day);
55             break;
56 
57         case'n':  //进入下个月
58             if (date.getMonth() == 12)
59                 date = Date(date.getYear() + 1, 1, 1);
60             else
61                 date = Date(date.getYear(), date.getMonth() + 1, 1);
62 
63             for (int i = 0; i < n; i++)
64                 accounts[i]->settle(date);
65 
66             break;
67         }
68 
69     } while (cmd != 'e');
70 }

运行测试截图：

总结：

1.改进：使用虚函数和抽象类，使项目实现了运行时多态，可以把各个账户放入数组中，简化了操作；将distance的求值，用“-”运算符重载，代码更易读，操作也更简单

2.问题：现实中利息不会一直固定不变

实验总结

1.在进行实验5的撰写时，代码报出了LN2019的错误，被足足硬控了好几个小时。

还好最后找到了官方的错误原因解释，以及修改方式：

看来自己在使用模板类时犯了常见且经典的错误，这一次的debug真是让人印象深刻。

posted on 2024-12-08 22:38 Forgiver 阅读(4) 评论(0) 编辑收藏举报

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