实验一 类与对象

#include <iostream>
#include <cmath>
using namespace std;
class complex {
public:
    complex(double m, double n = 0) : real{ m }, imag{ n }{}
    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;
}

#include "complex.hpp"
#include <iostream>
using namespace std;
int main()
{
    complex c1(3, -4);
    const complex c2(4.5);
    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;
}

 

#include<iostream>
using namespace std;
class User
{
public:
    User(string a, string p = "111111", string e = "") : name(a), password(p), email(e) { n++; }
    User(User& u) : name(u.name), password(u.password), email(u.email) { n++; }
    void set_email()
    {
        cout << "Enter email address:";
        cin >> email;
        cout << "email is set sucessfully..." << endl;
    }
    void change_passwd();
    void print_info()
    {
        cout << "name: " << name << endl;
        cout << "passwd:******" << endl;
        cout << "email :" << email << endl;
    }
    static void print_n()
    {
        cout << "there are " << n << " users." << endl;
    }
    ~User() { n--; }
private:
    string name;
    string password;
    string email;
    static int n;
};

int User::n = 0;

void User::change_passwd()
{
    int i = 0;
    string temp;
    while (i != 3)
    {
        if (i == 0)
            cout << "Enter old password:";
        else
            cout << "Please re-enter again:";
        cin >> temp;
        if (temp == password)
        {
            cout << "Enter new password:";
            cin >> password;
            while (password.length() != 6 || password.find('@') == -1)
            {
                cout << "The new password is wrong.";
                cout << "Please input again:";
                cin >> password;
            }
            cout << "new password is set sucessfully..." << endl;
            return;
        }
        else
        {
            cout << "password input error.";
            i++;
        }
    }
    if (i == 3)
        cout << "Please try after a while." << endl;
}

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

int main()
{
    using namespace std;

    cout << "testing 1......" << endl;
    User user1("Jonny", "92197", "xyz@hotmail.com");
    user1.print_info();

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

    User::print_n();
}

 总结：不能将头文件放到了源文件，会编译错误。比较深刻的理解了类与对象的运用,通过友元可以直接访问类的私有成员这一特性，可以更方便地实现操作。

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