實驗4 類的組合、繼承、模板類、標準庫

陆一鸣·發表於2024-11-25
繼承

實驗任務1：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
 1 #include <iostream>
 2 
 3 using std::cout;
 4 using std::endl;
 5 
 6 // 類A的定義
 7 class A {
 8 public:
 9     A(int x0, int y0);
10     void display() const;
11 
12 private:
13     int x, y;
14 };
15 
16 A::A(int x0, int y0): x{x0}, y{y0} {
17 }
18 
19 void A::display() const {
20     cout << x << ", " << y << endl;
21 }
22 
23 // 類B的定義
24 class B {
25 public:
26     B(double x0, double y0);
27     void display() const;
28 
29 private:
30     double x, y;
31 };
32 
33 B::B(double x0, double y0): x{x0}, y{y0} {
34 }
35 
36 void B::display() const {
37     cout << x << ", " << y << endl;
38 }
39 
40 void test() {
41     cout << "測試類A: " << endl;
42     A a(3, 4);
43     a.display();
44 
45     cout << "\n測試類B: " << endl;
46     B b(3.2, 5.6);
47     b.display();
48 }
49 
50 int main() {
51     test();
52 }
task1_1
實驗4 類的組合、繼承、模板類、標準庫 
 1 #include <iostream>
 2 #include <string>
 3 
 4 using std::cout;
 5 using std::endl;
 6 using std::string;
 7 
 8 // 定義類别範本
 9 template<typename T>
10 class X{
11 public:
12     X(T x0, T y0);
13     void display();
14 
15 private:
16     T x, y;
17 };
18 
19 template<typename T>
20 X<T>::X(T x0, T y0): x{x0}, y{y0} {
21 }
22 
23 template<typename T>
24 void X<T>::display() {
25     cout << x << ", " << y << endl;
26 }
27 
28 
29 void test() {
30     cout << "測試1: 類别範本X中的抽象型別T用int例項化" << endl;
31     X<int> x1(3, 4);
32     x1.display();
33     
34     cout << endl;
35 
36     cout << "測試2: 類别範本X中的抽象型別T用double例項化" << endl;
37     X<double> x2(3.2, 5.6);
38     x2.display();
39 
40     cout << endl;
41 
42     cout << "測試3: 類别範本X中的抽象型別T用string例項化" << endl;
43     X<string> x3("hello", "oop");
44     x3.display();
45 }
46 
47 int main() {
48     test();
49 }
task1_2

實驗任務2：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
  1 #include <iostream>
  2 #include <vector>
  3 #include <string>
  4 #include <algorithm>
  5 #include <numeric>
  6 #include <iomanip>
  7 
  8 using std::vector;
  9 using std::string;
 10 using std::cin;
 11 using std::cout;
 12 using std::endl;
 13 
 14 class GradeCalc: public vector<int> {
 15 public:
 16     GradeCalc(const string &cname, int size);      
 17     void input();                             // 錄入成績
 18     void output() const;                      // 輸出成績
 19     void sort(bool ascending = false);        // 排序 (預設降序)
 20     int min() const;                          // 返回最低分
 21     int max() const;                          // 返回最高分
 22     float average() const;                    // 返回平均分
 23     void info();                              // 輸出課程成績資訊 
 24 
 25 private:
 26     void compute();     // 成績統計
 27 
 28 private:
 29     string course_name;     // 課程名
 30     int n;                  // 課程人數
 31     vector<int> counts = vector<int>(5, 0);      // 儲存各分數段人數（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100]
 32     vector<double> rates = vector<double>(5, 0); // 儲存各分數段比例 
 33 };
 34 
 35 GradeCalc::GradeCalc(const string &cname, int size): course_name{cname}, n{size} {}   
 36 
 37 void GradeCalc::input() {
 38     int grade;
 39 
 40     for(int i = 0; i < n; ++i) {
 41         cin >> grade;
 42         this->push_back(grade);
 43     } 
 44 }  
 45 
 46 void GradeCalc::output() const {
 47     for(auto ptr = this->begin(); ptr != this->end(); ++ptr)
 48         cout << *ptr << " ";
 49     cout << endl;
 50 } 
 51 
 52 void GradeCalc::sort(bool ascending) {
 53     if(ascending)
 54         std::sort(this->begin(), this->end());
 55     else
 56         std::sort(this->begin(), this->end(), std::greater<int>());
 57 }  
 58 
 59 int GradeCalc::min() const {
 60     return *std::min_element(this->begin(), this->end());
 61 }  
 62 
 63 int GradeCalc::max() const {
 64     return *std::max_element(this->begin(), this->end());
 65 }    
 66 
 67 float GradeCalc::average() const {
 68     return std::accumulate(this->begin(), this->end(), 0) * 1.0 / n;
 69 }   
 70 
 71 void GradeCalc::compute() {
 72     for(int grade: *this) {
 73         if(grade < 60)
 74             counts.at(0)++;
 75         else if(grade >= 60 && grade < 70)
 76             counts.at(1)++;
 77         else if(grade >= 70 && grade < 80)
 78             counts.at(2)++;
 79         else if(grade >= 80 && grade < 90)
 80             counts.at(3)++;
 81         else if(grade >= 90)
 82             counts.at(4)++;
 83     }
 84 
 85     for(int i = 0; i < rates.size(); ++i)
 86         rates.at(i) = counts.at(i) * 1.0 / n;
 87 }
 88 
 89 void GradeCalc::info()  {
 90     cout << "課程名稱:\t" << course_name << endl;
 91     cout << "排序後成績: \t";
 92     sort();  output();
 93     cout << "最高分:\t" << max() << endl;
 94     cout << "最低分:\t" << min() << endl;
 95     cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << endl;
 96     
 97     compute();  // 統計各分數段人數、比例
 98 
 99     vector<string> tmp{"[0, 60)  ", "[60, 70)", "[70, 80)","[80, 90)", "[90, 100]"};
100     for(int i = tmp.size()-1; i >= 0; --i)
101         cout << tmp[i] << "\t: " << counts[i] << "人\t" 
102              << std::fixed << std::setprecision(2) << rates[i]*100 << "%" << endl; 
103 }
gradecalc.hpp
實驗4 類的組合、繼承、模板類、標準庫 
 1 #include "GradeCalc.hpp"
 2 #include <iomanip>
 3 
 4 void test() {
 5     int n;
 6     cout << "輸入班級人數: ";
 7     cin >> n;
 8 
 9     GradeCalc c1("OOP", n);
10 
11     cout << "錄入成績: " << endl;;
12     c1.input();
13     cout << "輸出成績: " << endl;
14     c1.output();
15 
16     cout << string(20, '*') + "課程成績資訊"  + string(20, '*') << endl;
17     c1.info();
18 }
19 
20 int main() {
21     test();
22 }
demo2.cpp

執行結果截圖：

問題：

問題1：

類GradeCalc繼承自vector,成績儲存在vector 中；

透過繼承而來的begin()和end()訪問到每個成績；

input透過繼承來的push_back()實現資料存入物件。

問題2：

作為除數，總分除以總人數即可得到平均分；

會有影響，乘1.0是為了將被除數轉化為浮點數，以便得到更為精確的平均分。

問題3：

1、沒有對成績的輸入進行合法性檢驗。

實驗任務3：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
  1 #include <iostream>
  2 #include <vector>
  3 #include <string>
  4 #include <algorithm>
  5 #include <numeric>
  6 #include <iomanip>
  7 
  8 using std::vector;
  9 using std::string;
 10 using std::cin;
 11 using std::cout;
 12 using std::endl;
 13 
 14 class GradeCalc {
 15 public:
 16     GradeCalc(const string &cname, int size);      
 17     void input();                             // 錄入成績
 18     void output() const;                      // 輸出成績
 19     void sort(bool ascending = false);        // 排序 (預設降序)
 20     int min() const;                          // 返回最低分
 21     int max() const;                          // 返回最高分
 22     float average() const;                    // 返回平均分
 23     void info();                              // 輸出課程成績資訊 
 24 
 25 private:
 26     void compute();     // 成績統計
 27 
 28 private:
 29     string course_name;     // 課程名
 30     int n;                  // 課程人數
 31     vector<int> grades;     // 課程成績
 32     vector<int> counts = vector<int>(5, 0);      // 儲存各分數段人數（[0, 60), [60, 70), [70, 80), [80, 90), [90, 100]
 33     vector<double> rates = vector<double>(5, 0); // 儲存各分數段比例 
 34 };
 35 
 36 GradeCalc::GradeCalc(const string &cname, int size): course_name{cname}, n{size} {}   
 37 
 38 void GradeCalc::input() {
 39     int grade;
 40 
 41     for(int i = 0; i < n; ++i) {
 42         cin >> grade;
 43         grades.push_back(grade);
 44     } 
 45 }  
 46 
 47 void GradeCalc::output() const {
 48     for(int grade: grades)
 49         cout << grade << " ";
 50     cout << endl;
 51 } 
 52 
 53 void GradeCalc::sort(bool ascending) {
 54     if(ascending)
 55         std::sort(grades.begin(), grades.end());
 56     else
 57         std::sort(grades.begin(), grades.end(), std::greater<int>());
 58         
 59 }  
 60 
 61 int GradeCalc::min() const {
 62     return *std::min_element(grades.begin(), grades.end());
 63 }  
 64 
 65 int GradeCalc::max() const {
 66     return *std::max_element(grades.begin(), grades.end());
 67 }    
 68 
 69 float GradeCalc::average() const {
 70     return std::accumulate(grades.begin(), grades.end(), 0) * 1.0 / n;
 71 }   
 72 
 73 void GradeCalc::compute() {
 74     for(int grade: grades) {
 75         if(grade < 60)
 76             counts.at(0)++;
 77         else if(grade >= 60 && grade < 70)
 78             counts.at(1)++;
 79         else if(grade >= 70 && grade < 80)
 80             counts.at(2)++;
 81         else if(grade >= 80 && grade < 90)
 82             counts.at(3)++;
 83         else if(grade >= 90)
 84             counts.at(4)++;
 85     }
 86 
 87     for(int i = 0; i < rates.size(); ++i)
 88         rates.at(i) = counts.at(i) *1.0 / n;
 89 }
 90 
 91 void GradeCalc::info()  {
 92     cout << "課程名稱:\t" << course_name << endl;
 93     cout << "排序後成績: \t";
 94     sort();  output();
 95     cout << "最高分:\t" << max() << endl;
 96     cout << "最低分:\t" << min() << endl;
 97     cout << "平均分:\t" << std::fixed << std::setprecision(2) << average() << endl;
 98     
 99     compute();  // 統計各分數段人數、比例
100 
101     vector<string> tmp{"[0, 60)  ", "[60, 70)", "[70, 80)","[80, 90)", "[90, 100]"};
102     for(int i = tmp.size()-1; i >= 0; --i)
103         cout << tmp[i] << "\t: " << counts[i] << "人\t" 
104              << std::fixed << std::setprecision(2) << rates[i]*100 << "%" << endl; 
105 }
gradecalc.hpp
實驗4 類的組合、繼承、模板類、標準庫 
 1 #include "GradeCalc.hpp"
 2 #include <iomanip>
 3 
 4 void test() {
 5     int n;
 6     cout << "輸入班級人數: ";
 7     cin >> n;
 8 
 9     GradeCalc c1("OOP", n);
10 
11     cout << "錄入成績: " << endl;;
12     c1.input();
13     cout << "輸出成績: " << endl;
14     c1.output();
15 
16     cout << string(20, '*') + "課程成績資訊"  + string(20, '*') << endl;
17     c1.info();
18 }
19 
20 int main() {
21     test();
22 }
demo3.cpp

執行結果截圖：

問題：

問題1：

成績儲存在GradeCalc類中的一個vector型別的私有成員變數grades中；

透過直接訪問grades物件來訪問每個成績；

實驗2是透過繼承的vector 介面來隱性訪問各個成績，而實驗3則透過顯性訪問GradeCalc類中的一個vector型別的私有成員變數grades來訪問各個成績；

問題2：

在物件導向程式設計的過程中，類的射擊方式多種多樣，既可以透過繼承來實現程式碼複用，也可以載類中新增另一個類的物件來實現。

實驗任務4：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
 1 #include <iostream>
 2 #include <string>
 3 #include <limits>
 4 
 5 using namespace std;
 6 
 7 void test1() {
 8     string s1, s2;
 9     cin >> s1 >> s2;  // cin: 從輸入流讀取字串, 碰到空白符(空格/回車/Tab)即結束
10     cout << "s1: " << s1 << endl;
11     cout << "s2: " << s2 << endl;
12 }
13 
14 void test2() {
15     string s1, s2;
16     getline(cin, s1);  // getline(): 從輸入流中提取字串，直到遇到換行符
17     getline(cin, s2);
18     cout << "s1: " << s1 << endl;
19     cout << "s2: " << s2 << endl;
20 }
21 
22 void test3() {
23     string s1, s2;
24     getline(cin, s1, ' '); //從輸入流中提取字串，直到遇到指定分隔符
25     getline(cin, s2);
26     cout << "s1: " << s1 << endl;
27     cout << "s2: " << s2 << endl;
28 }
29 
30 int main() {
31     cout << "測試1: 使用標準輸入流物件cin輸入字串" << endl;
32     test1();
33     cout << endl;
34 
35     cin.ignore(numeric_limits<streamsize>::max(), '\n');
36 
37     cout << "測試2: 使用函式getline()輸入字串" << endl;
38     test2();
39     cout << endl;
40 
41     cout << "測試3: 使用函式getline()輸入字串, 指定字串分隔符" << endl;
42     test3();
43 }
task4_1

執行結果截圖：

問題1：

用途：忽略輸入緩衝區中剩餘的字元，以防錄入字元時受到多餘換行符的影響。

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
 1 #include <iostream>
 2 #include <string>
 3 #include <vector>
 4 #include <limits>
 5 
 6 using namespace std;
 7 
 8 void output(const vector<string> &v) {
 9     for(auto &s: v)
10         cout << s << endl;
11 }
12 
13 void test() {
14     int n;
15     while(cout << "Enter n: ", cin >> n) {
16         vector<string> v1;
17 
18         for(int i = 0; i < n; ++i) {
19             string s;
20             cin >> s;
21             v1.push_back(s);
22         }
23 
24         cout << "output v1: " << endl;
25         output(v1); 
26         cout << endl;
27     }
28 }
29 
30 int main() {
31     cout << "測試: 使用cin多組輸入字串" << endl;
32     test();
33 }
task4_2

執行結果截圖：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
 1 #include <iostream>
 2 #include <string>
 3 #include <vector>
 4 #include <limits>
 5 
 6 using namespace std;
 7 
 8 void output(const vector<string> &v) {
 9     for(auto &s: v)
10         cout << s << endl;
11 }
12 
13 void test() {
14     int n;
15     while(cout << "Enter n: ", cin >> n) {
16         cin.ignore(numeric_limits<streamsize>::max(), '\n');
17 
18         vector<string> v2;
19 
20         for(int i = 0; i < n; ++i) {
21             string s;
22             getline(cin, s);
23             v2.push_back(s);
24         }
25         cout << "output v2: " << endl;
26         output(v2); 
27         cout << endl;
28     }
29 }
30 
31 int main() {
32     cout << "測試: 使用函式getline()多組輸入字串" << endl;
33     test();
34 }
task4_3

執行結果截圖：

問題2：

用途：每次迴圈開始前，忽略快取區中剩餘的字元，直到遇到換行符。

實驗任務5：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
 1 #include "grm.hpp"
 2 #include <iostream>
 3 
 4 using std::cout;
 5 using std::endl;
 6 
 7 void test1() {
 8     GameResourceManager<float> HP_manager(99.99);
 9     cout << "當前生命值: " << HP_manager.get() << endl;
10     HP_manager.update(9.99);
11     cout << "增加9.99生命值後, 當前生命值: " << HP_manager.get() << endl;
12     HP_manager.update(-999.99);
13     cout << "減少999.99生命值後, 當前生命值: " << HP_manager.get() << endl;
14 }
15 
16 void test2() {
17     GameResourceManager<int> Gold_manager(100);
18     cout << "當前金幣數量: " << Gold_manager.get() << endl;
19     Gold_manager.update(50);
20     cout << "增加50個金幣後, 當前金幣數量: " << Gold_manager.get() << endl;
21     Gold_manager.update(-99);
22     cout << "減少99個金幣後, 當前金幣數量: " << Gold_manager.get() << endl;
23 }
24 
25 
26 int main() {
27     cout << "測試1: 用float型別對類别範本GameResourceManager例項化" << endl;
28     test1();
29     cout << endl;
30 
31     cout << "測試2: 用int型別對類别範本GameResourceManager例項化" << endl;
32     test2();
33 }
task5.cpp
實驗4 類的組合、繼承、模板類、標準庫 
 1 template<typename resource>
 2 class GameResourceManager {
 3 public:
 4     GameResourceManager(resource a);
 5     resource get();
 6     void update(resource b);
 7 private:
 8     resource m1;
 9 };
10 template<typename resource>
11 GameResourceManager<resource>::GameResourceManager(resource a):m1(a){}
12 template<typename resource>
13 resource GameResourceManager<resource>::get() { return m1; }
14 template<typename resource>
15 void GameResourceManager<resource>::update(resource b) { m1 += b; if (m1 < 0)m1 = 0; }
grm.hpp

執行結果截圖：

實驗任務6：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 class Info {
 5 public:
 6     Info(const string& nickname, const string& contact, const string& city, int n);
 7     void display()const;
 8 
 9 private:
10     string nickname;
11     string contact;
12     string city;
13     int n;
14 };
15 
16 Info::Info(const string& nickname, const string& contact, const string& city, int n): nickname(nickname), contact(contact), city(city), n(n) {}
17 
18 void Info::display()const{
19     cout << "暱稱: " << nickname << endl;
20     cout << "聯絡方式: " << contact << endl;
21     cout << "所在城市: " << city << endl;
22     cout << "預定人數: " << n << endl;
23 }
info.hpp
實驗4 類的組合、繼承、模板類、標準庫 
 1 #include "info.hpp"
 2 #include <iostream>
 3 #include <vector>
 4 using namespace std;
 5 const int capacity = 100;
 6 
 7 void inputInfo(vector<Info>& audience_lst) {
 8     int total = 0;
 9     cout << "錄入使用者預約資訊:" << endl<<endl;
10     cout << "暱稱    聯絡方式(郵箱/手機號)   所在城市   預定參加人數" << endl;
11     while (true) {
12         string nickname, contact, city;
13         int n;
14         /*cout << "錄入使用者預約資訊:" << endl;
15         cout << "暱稱    聯絡方式(郵箱/手機號)   所在城市   預定參加人數" << endl;*/
16         if (!(cin >> nickname >> contact >> city >> n)) {
17             break;
18         }
19         if (total + n > capacity) {
20             cout << "對不起,只剩 " << capacity - total << " 個位置." <<endl<<"1.輸入u,更新(update)預定資訊"<<endl<<"2.輸入q,退出預定" << endl;
21             cout << "你的選擇：";
22             string choice;
23             cin >> choice;
24             if (choice == "u") {
25                 cout << "請重新輸入預定資訊:" << endl;
26                 continue;
27             }
28             else if (choice == "q") {
29                 break;
30             }
31         }
32         total += n;
33         audience_lst.push_back(Info(nickname, contact, city, n));
34         if (total >= capacity) {
35             cout << "截至目前,一共有 " << capacity << " 位聽眾預約。" << endl;
36             break;
37         }
38     }
39 }
40 
41 void printInfo(const vector<Info>& audience_lst) {
42     cout << "預約聽眾資訊如下:" << endl;
43     for (const Info& info : audience_lst) {
44         info.display();
45         cout << endl;
46     }
47 }
48 
49 int main() {
50     vector<Info> audience_lst;
51     inputInfo(audience_lst);
52     printInfo(audience_lst);
53     return 0;
54 }
task6.cpp

執行結果截圖：

實驗任務7：

實驗程式碼：

實驗4 類的組合、繼承、模板類、標準庫 
 1 #ifndef __DATE_H__
 2 #define __DATE_H__
 3 class Date {
 4 private:
 5     int year;
 6     int month;
 7     int day;
 8     int totalDays;
 9 public:
10     Date(int year, int month, int day);
11     int getYear() const { return year; }
12     int getMonth() const { return month; }
13     int getDay() const { return day; }
14     int getMaxDay() const;
15     bool isLeapYear() const {
16         return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
17     }
18     void show() const;
19 
20     int distance(const Date& date) const {
21         return totalDays - date.totalDays;
22     }
23 };
24 #endif //__DATE_H__
date.h
實驗4 類的組合、繼承、模板類、標準庫 
 1 #include "date.h"
 2 #include <iostream>
 3 #include <cstdlib>
 4 using namespace std;
 5 namespace {
 6     const int DAYS_BEFORE_MONTH[] = { 0,31,59,90,120,151,181,212,243,273,304,334,365 };
 7 }
 8 Date::Date(int year, int month, int day) :year(year), month(month), day(day) {
 9     if (day <= 0 || day > getMaxDay()) {
10         cout << "Invalid date:";
11         show();
12         cout << endl;
13         exit(1);
14     }
15     int years = year - 1;
16     totalDays = years * 365 + years / 4 - years / 100 + years / 400 + DAYS_BEFORE_MONTH[month - 1] + day;
17     if (isLeapYear() && month > 2) totalDays++;
18 }
19 
20 int Date::getMaxDay() const {
21     if (isLeapYear() && month == 2)
22         return 29;
23     else
24         return DAYS_BEFORE_MONTH[month] - DAYS_BEFORE_MONTH[month - 1];
25 }
26 
27 void Date::show()  const {
28     cout << getYear() << "-" << getMonth() << "-" << getDay();
29 }
date.cpp
實驗4 類的組合、繼承、模板類、標準庫 
 1 #pragma once
 2 #ifndef  ACCUMULATOR H
 3 #define  ACCUMULATOR H
 4 #include"date.h"
 5 class Accumulator {
 6 private:
 7     Date lastDate;
 8     double value;
 9     double sum;
10 public:
11     Accumulator(const Date& date, double value) :lastDate(date), value(value), sum{ 0 } {
12     }
13 
14     double getSum(const Date& date)const {
15         return sum + value * date.distance(lastDate);
16     }
17 
18     void change(const Date& date, double value) {
19         sum = getSum(date);
20         lastDate = date; this->value = value;
21     }
22 
23     void reset(const Date& date, double value) {
24         lastDate = date; this->value = value; sum = 0;
25     }
26 };
27 #endif//ACCUMULATOR H
accumulator.h
實驗4 類的組合、繼承、模板類、標準庫 
 1 #pragma once
 2 #ifndef  ACCOUNT H
 3 #define  ACCOUNT H
 4 #include"date.h"
 5 #include"accumulator.h"
 6 #include<string>
 7 class Account {
 8 private:
 9     std::string id;
10     double balance;
11     static double total;
12 protected:
13     Account(const Date& date, const std::string& id);
14     void record(const Date& date, double amount, const std::string& desc);
15     void error(const std::string& msg)const;
16 public:
17     const std::string& getId()const { return id; }
18     double getBalance()const { return balance; }
19     static double getTotal() { return total; }
20 
21     void show()const;
22 };
23 class SavingsAccount :public Account {
24 private:
25     Accumulator acc;
26     double rate;
27 public:
28     SavingsAccount(const Date& date, const std::string& id, double rate);
29     double getRate()const { return rate; }
30 
31     void deposit(const Date& date, double amount, const std::string& desc);
32     void withdraw(const Date& date, double amount, const std::string& desc);
33     void settle(const Date& date);
34 };
35 class CreditAccount :public Account {
36 private:
37     Accumulator acc;
38     double credit;
39     double rate;
40     double fee;
41     double getDebt()const {
42         double balance = getBalance();
43         return (balance < 0 ? balance : 0);
44     }
45 public:
46     CreditAccount(const Date& date, const std::string& id, double credit, double rate, double fee);
47     double getCredit()const { return credit; }
48     double getRate()const { return rate; }
49     double getAvailableCredit()const {
50         if (getBalance() < 0)
51             return credit + getBalance();
52         else
53             return credit;
54     }
55     void deposit(const Date& date, double amount, const std::string& desc);
56     void withdraw(const Date& date, double amount, const std::string& desc);
57     void settle(const Date& date);
58     void show()const;
59 };
60 #endif//ACCOUNT H
account.h
實驗4 類的組合、繼承、模板類、標準庫 
 1 #include"account.h"
 2 #include<cmath>
 3 #include<iostream>
 4 using namespace std;
 5 double Account::total = 0;
 6 
 7 Account::Account(const Date& date, const string& id) :id{ id }, balance{ 0 } {
 8     date.show(); cout << "\t#" << id << "created" << endl;
 9 }
10 
11 
12 void Account::record(const Date& date, double amount, const string& desc) {
13     amount = floor(amount * 100 + 0.5) / 100;
14     balance += amount;
15     total += amount;
16     date.show();
17     cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl;
18 }
19 
20 void Account::show()const { cout << id << "\tBalance:" << balance; }
21 void Account::error(const string& msg)const {
22     cout << "Error(#" << id << "):" << msg << endl;
23 }
24 
25 SavingsAccount::SavingsAccount(const Date& date, const string& id, double rate) :Account(date, id), rate(rate), acc(date, 0) {}
26 
27 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) {
28     record(date, amount, desc);
29     acc.change(date, getBalance());
30 }
31 
32 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) {
33     if (amount > getBalance()) {
34         error("not enough money");
35     }
36     else {
37         record(date, -amount, desc);
38         acc.change(date, getBalance());
39     }
40 }
41 
42 void SavingsAccount::settle(const Date& date) {
43     double interest = acc.getSum(date) * rate / date.distance(Date(date.getYear() - 1, 1, 1));
44     if (interest != 0)record(date, interest, "interest");
45     acc.reset(date, getBalance());
46 }
47 
48 CreditAccount::CreditAccount(const Date& date, const string& id, double credit, double rate, double fee) :Account(date, id), credit(credit), rate(rate), fee(fee), acc(date, 0) {}
49 
50 void CreditAccount::deposit(const Date& date, double amount, const string& desc) {
51     record(date, amount, desc);
52     acc.change(date, getDebt());
53 }
54 
55 void CreditAccount::withdraw(const Date& date, double amount, const string& desc) {
56     if (amount - getBalance() > credit) {
57         error("not enough credit");
58     }
59     else {
60         record(date, -amount, desc);
61         acc.change(date, getDebt());
62     }
63 }
64 
65 void CreditAccount::settle(const Date& date) {
66     double interest = acc.getSum(date) * rate;
67     if (interest != 0)record(date, interest, "interest");
68     if (date.getMonth() == 1)
69         record(date, -fee, "annual fee");
70     acc.reset(date, getDebt());
71 }
72 
73 void CreditAccount::show()const {
74     Account::show();
75     cout << "\tAvailable credit:" << getAvailableCredit();
76 }
account.cpp
實驗4 類的組合、繼承、模板類、標準庫 
 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     sa1.deposit(Date(2008, 11, 5), 5000, "salary");
13     ca.withdraw(Date(2008, 11, 15), 2000, "buy a cell");
14     sa2.deposit(Date(2008, 11, 25), 10000, "sell stock 0323");
15 
16     ca.settle(Date(2008, 12, 1));
17 
18     ca.deposit(Date(2008, 12, 1), 2016, "repay the credit");
19     sa1.deposit(Date(2008, 12, 5), 5500, "salary");
20 
21     sa1.settle(Date(2009, 1, 1));
22     sa2.settle(Date(2009, 1, 1));
23     ca.settle(Date(2009, 1, 1));
24 
25     cout << endl;
26     sa1.show(); cout << endl;
27     sa2.show(); cout << endl;
28     ca.show(); cout << endl;
29     cout << "Total:" << Account::getTotal() << endl;
30     return 0;
31 }
7_10.cpp

執行結果截圖：

改進：運用了類的派生的思想，使得派生類處理每一筆具體賬目時可以呼叫record函式來改變餘額並輸出賬目資訊，提高了程式碼複用性。

不足：兩個派生類SavingAccount和CreditAccount雖然具有相同的成員函式，但由於其實現不同，只能在派生類中給出他們的實現。

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