实验一 类与对象

实验任务三

//Complex.hpp
#include<iostream>
#include<cmath>

using namespace std;

class Complex
{
    public:
        Complex() : real{0}, imag{0} {};
        Complex(double r, double i = 0.0) : real{r}, imag{i} {};
        Complex(const Complex &obj) : real{obj.real}, imag{obj.imag} {};

        double get_real() const;
        double get_imag() const;
        
        void show() const;
        void add(const Complex &x);

        friend Complex add(const Complex &a, const Complex &b);
        friend bool is_equal(const Complex &a, const Complex &b);
        friend double abs(const Complex &x);

    private:
        double real, 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 << " - " << imag*(-1) << "i";
    else
      cout << real;
}

void Complex::add(const Complex &x)
{
    real += x.real;
    imag += x.imag;
}

Complex add(const Complex &a, const Complex &b)
{
    Complex ans;
    ans.real = a.real + b.real;
    ans.imag = a.imag + b.imag;
    return ans;
}

bool is_equal(const Complex &a, const Complex &b)
{
    if(a.real == b.real && a.imag == b.imag)
      return true;
    else 
      return false;
}

double abs(const Complex &x)
{
    double ans = x.real*x.real + x.imag*x.imag;
    ans = sqrt(ans);
    return ans;
}

//task3.cpp
#include "Complex.hpp"
#include <iostream>

int main()
{
    using namespace std;

    Complex c1(2.3, -4.9);
    const Complex c2(5.4);
    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;
}

 实验任务4

//User.hpp
#include<iostream>
#include<string>

using namespace std;

class User
{
    public:
        User(string name, string p = "111111", string e = "");
        void set_email();
        void change_passwd();
        void print_info();
        static void print_n();
    private:
        string name, passwd, email;
        static int n;
};
int User::n = 0;
User::User(string name, string p/*="111111"*/, string e/*=""*/) : name{name}, passwd{p}, email{e} {n++;}
void User::set_email()
{
    cout << "Enter email address: ";
    cin >> email;
    cout << "email is set successfully..." << endl;
}
void User::change_passwd()
{
    string temp;
    cout << "Enter old password: ";
    int count = 3;
    while(count)
    {
        cin >> temp;
        if(temp == passwd)
        {
            cout << "Enter new passwd: ";
            cin >> passwd;
            cout << "new passwd is set successfully..." << endl;
            break;
        }
        else
        {
            count--;
            if(count != 0)
              cout << "password input error. Please re-enter again: ";
        }
    }
    if(count == 0)
      cout << "password input error. Please try after a while." << endl;
}
void User::print_info()
{
    cout << "name:   " << name << endl;
    cout << "passwd: " << "******" << endl;
    cout << "email:  " << email << endl;
}
void User::print_n()
{
    cout << "there are " << n << " users." << endl;
}

 

//task4.cpp
#include "User.hpp"
#include <iostream>

int main()
{
    using namespace std;

    cout << "testing 1......" << endl;
    User user1("Bob", "114514", "hotdog@gmail.com");
    user1.print_info();

    cout << endl
         << "testing 2......" << endl
         << endl;
    User user2("Alice");
    user2.change_passwd();
    user2.set_email();
    user2.print_info();

    User::print_n();
}

 

 实验总结：

        1.函数成员如果没有修改数据成员的需求，可加const来保护数据成员，使程序更加安全

        2.访问静态成员需要通过静态函数成员