实验1 类与对象

四、实验结论

1.实验任务1-2

2.实验任务3

• Complex.hpp文件源码：

  #ifndef Complex_hpp
  #define Complex_hpp
  #include <iostream>
  #include <cmath>
  using namespace std;
  
  class Complex
  {
  public:
    Complex(){};
    Complex(double x);
    Complex(double x, double y);
    Complex(const Complex &c);
    ~Complex() = default;
    double get_real() const;
    double get_imag() const;
    void show() const;
    void add(const Complex &c);
    friend Complex add(const Complex &c1, const Complex &c2);
    friend bool is_equal(const Complex &c1, const Complex &c2);
    friend double abs(const Complex &c);
  
  private:
    double real, imag;
  };
  
  Complex::Complex(double x, double y) : real{x}, imag{y} {}
  Complex::Complex(double x) : real{x}, imag{0.0} {}
  Complex::Complex(const Complex &c) : real(c.real), imag(c.imag) {}
  
  double Complex::get_real() const
  {
    return real;
  }
  
  double Complex::get_imag() const
  {
    return imag;
  }
  void Complex::show() const
  {
    if (imag > 0)
       cout << real << "+" << imag << "i";
    else if (imag == 0)
       cout << real;
    else
       cout << real << imag << "i";
  }
  void Complex::add(const Complex &c)
  {
    real += c.real;
    imag += c.imag;
  }
  
  Complex add(const Complex &c1, const Complex &c2)
  {
    Complex c;
    c.imag = c1.imag + c2.imag;
    c.real = c1.real + c2.real;
    return c;
  }
  
  bool is_equal(const Complex &c1, const Complex &c2)
  {
    if (c1.imag == c2.imag && c1.real == c2.real)
       return true;
    else
       return false;
  }
  
  double abs(const Complex &c)
  {
    return sqrt(c.imag * c.imag + c.real * c.real);
  }
  #endif
  

• task3.cpp源码

  #include "Complex.hpp"
  #include <iostream>
  using namespace std;
  
  int main()
  {
    Complex c1(1, -17);
    const Complex c2(3.6);
    Complex c3(c1);
    cout << "c1 = ";
    c1.show();
    cout << endl;
    cout << "c2 = ";
    c2.show();
    cout << endl;
    cout << "c2.imag = " << c2.get_imag() << endl;
    cout << "c3 = ";
    c3.show();
    cout << endl;
    cout << "abs(c1) = ";
    cout << abs(c1) << endl;
    cout << boolalpha;
    cout << "c1 == c3 : " << is_equal(c1, c3) << endl;
    cout << "c1 == c2 : " << is_equal(c1, c2) << endl;
    Complex c4;
    c4 = add(c1, c2);
    cout << "c4 = c1 + c2 = ";
    c4.show();
    cout << endl;
    c1.add(c2);
    cout << "c1 += c2, "
        << "c1 = ";
    c1.show();
    cout << endl;
  }
  

• 运行测试结果截图

  

3.实验任务4

• User.hpp文件源码

  #ifndef USER_HPP
  #define USER_HPP
  #include <iostream>
  #include <cstring>
  using namespace std;
  
  class User
  {
  public:
    User(string n);
    User(string n, string p, string e);
    ~User(){};
    void set_email();
    void change_passwd();
    void print_info();
    static void print_n();
  
  private:
    string name, passwd, email;
    static int num;
  };
  
  int User::num = 0;
  
  User::User(string n) : name{n}, passwd{"111111"}, email{""}
  {
    ++num;
  }
  
  User::User(string n, string p, string e) : name{n}, passwd{p}, email{e}
  {
    ++num;
  }
  
  void User::set_email()
  {
    cout << "Enter email address: ";
    cin >> email;
    cout << "email is set successfully..." << endl;
  }
  
  void User::change_passwd()
  {
    string oldpsw;
    int error = 0;
    cout << "Enter old password:";
    cin >> oldpsw;
    while (oldpsw != passwd)
    {
       if ((++error) == 3)
         break;
       cout << "password input error. Please re-enter again:";
       cin >> oldpsw;
    }
    if (error == 3)
    {
       cout << "password input error. Please try for a while." << endl;
    }
    else
    {
       cout << "Enter new password:";
       cin >> passwd;
       cout << "new passwd is set successfully..." << endl;
    }
  }
  
  void User::print_info()
  {
    cout << "name:  " << name << endl;
    cout << "passwd: "
        << "******" << endl;
    cout << "email:  " << email << endl;
  }
  
  void User::print_n()
  {
    if (num == 1)
    {
       cout << "there is 1 user." << endl;
    }
    else
    {
       cout << "there are " << num << " users." << endl;
    }
  }
  #endif
  

• task4.cpp源码

  #include "User.hpp"
  #include <iostream>
  
  int main()
  {
    using namespace std;
    cout << "testing 1......" << endl;
    User user1("wyx117", "01117", "973047895@qq.com");
    user1.print_info();
    cout << endl
        << "testing 2......" << endl
        << endl;
    User user2("yy");
    user2.change_passwd();
    user2.set_email();
    user2.print_info();
    User::print_n();
  }
  

• 运行测试结果截图

  

五、实验总结

因为很早就接触编程语言、接触算法竞赛，所以C++的基本语法已相当熟练，但是对面向对象的内容，比如类的运用，这块知识是空缺的。通过学习这门课，动手做了这些实验，让我感受到类的方便，尤其对我这种强迫症患者，这种层次分明的结构让我很舒适。
字符串的比较让我犹豫了一下，一开始写的是strcmp(oldpsw,passwd)!=0，报错*不存在从"std::__cxx11::string" 到 "const char " 的适当转换函数，后来我想起来C++中可以直接比较就换成了oldpsw != passwd。