task3：

Complex.hpp源码：

#ifndef Complex_hpp
#define Complex_hpp

#include <iostream>
#include <cmath>

using namespace std;

class Complex {
public:
    Complex(double a, double b = 0) : real { a }, imag { b }{}
    Complex(Complex const& ci) : real { ci.real }, imag { ci.imag }{}
    Complex() = default;
    double get_real()const
    {
        return real;
    }
    double get_imag()const
    {
        return imag;
    }
    void show()const
    {
        if ( imag > 0 ) {
            cout << real << " + " << imag << "i";
        }
        else if ( imag < 0 ) {
            cout << real << " - " << -imag << "i";
        }
        else {
            cout << real;
        }
    }
    void add(Complex const& ci)
    {
        real += ci.real;
        imag += ci.imag;
    }
    friend Complex add(Complex const& c1, Complex const& c2);
    friend bool is_equal(Complex const& c1, Complex const& c2);
    friend double abs(Complex const& ci);
private:
    double real;
    double imag;
};
Complex add(Complex const& c1, Complex const& c2)
{
    Complex c3(0, 0);
    c3.real = c1.real + c2.real;
    c3.imag = c1.imag + c2.imag;
    return c3;
}
bool is_equal(Complex const& c1, Complex const& c2)
{
    if ( c1.real == c2.real && c1.imag == c2.imag ) {
        return true;
    }
    else {
        return false;
    }
}
double abs(Complex const& ci)
{
    double res = sqrt(ci.real * ci.real + ci.imag * ci.imag);
    return res;
}
#endif

 

Complex.cpp源码：

#include "Complex.hpp"
#include <iostream>

int main()
{
    using namespace std;

    Complex c1(6, -8);
    const Complex c2(4.2);
    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;
}

测试结果：

 

................................................

task4：

User.hpp源码：

#ifndef User_hpp
#define User_hpp

#include <iostream>
#include <string>

using namespace std;
const int N = 1e3;

class User {
public:
    User(string na, string p = "111111", string e = "") :name { na }, passwd { p }, email { e }
    {
        n++;
    }
    void set_email()
    {
        cout << "Enter email address: ";
        cin >> email;
    }
    void change_passwd()
    {
        string tmp;
        int cnt = 0;
        cout << "Enter old password: ";
        cin >> tmp;
        while (1) {
            if ( tmp == passwd ) {
                cout << "Enter new passwd: ";
                cin >> tmp;
                cout << "new passwd is set successfully..." << endl;
                passwd = tmp;
                break;
            }
            else {
                cnt++;
                if ( cnt == 3 ) {
                    cout << "password input error. Please try after a while." << endl;
                    break;
                }
                cout << "password input error. Please re-enter again: ";
                cin >> tmp;
            }
        }
    }
    void print_info()
    {
        cout << "name:   " << name << endl;
        cout << "passwd: ******" << endl;
        cout << "email:  " << email << endl;
    }
    static void print_n()
    {
        cout << "there are " << n << " users." << endl;
    }
private:
    string name;
    string passwd;
    string email;
    static int n;
};
int User::n = 0;
#endif

 

User.cpp源码：

#include "User.hpp"
#include <iostream>

int main()
{
    using namespace std;

    cout << "testing 1......" << endl;
    User user1("Rom", "114514514114", "Rom@163.com");
    user1.print_info();

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

    User::print_n();
}

测试结果：

 

 

 

 实验总结：

比较深刻的理解了类与对象的运用。通过实验巩固了对const的理解并且学会了通过static来定义类属性即通过类名就可以访问该成员。理解了友元的应用，通过友元可以直接访问类的私有成员这一特性，可以更方便地实现一些操作。