实验1 类与对象

1、实验任务3

• 程序源码

• Complex.hpp

#ifndef COMPLEX_HPP
#define COMPLEX_HPP
#include <iostream>
#include <iomanip>
#include <string>
#include <math.h>
using namespace std;
class Complex
{
public:
    Complex(){
    };
    Complex(double r,double i);
    Complex(double r);
    Complex(const Complex &c);
    ~Complex(){};
    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;
    double imag;
};
Complex::Complex(double r,double i):real(r),imag(i){}
Complex::Complex(double r):real(r),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)
        return true;
    else
        return false;
}
double abs(const Complex &c){
    return sqrt(c.imag*c.imag+c.real*c.real);
}
#endif

 

• • task3.cpp

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

int main()
{
    using namespace std;

    Complex c1(6, -8);
    const Complex c2(5.5);
    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;
}

• 运行测试结果截图

 

 

 

2、实验任务4

• 程序源码

• User.hpp

#ifndef USER_HPP
#define USER_HPP
#include <iostream>
#include <iomanip>
#include <string>
#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;
        string passwd;
        string 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(){
    string input;
    cout<<"Enter email address:";
    cin>>input;
    email=input;
    cout<<"email is set successfully..."<<endl;
}
void User::change_passwd() {
    cout<<"Enter old password:";
    string oldpsw;
    cin>>oldpsw;
    if(strcmp(oldpsw.c_str(),passwd.c_str())==0)//第一次 
    {
        cout<<"Enter new password:";
        string newpsw;
        cin>>newpsw;
        passwd=newpsw;
        cout<<"new passwd is set successfully..."<<endl;
    }
    else
    {
        cout<<"password input error. Please re-enter again:";
        string sec;
        cin>>sec;
        if(strcmp(sec.c_str(),passwd.c_str())==0)//第二次
        {
            cout<<"Enter new password:";
            string newpsw;
            cin>>newpsw;
            passwd=newpsw;
            cout<<"new passwd is set successfully..."<<endl;
        } 
        else
        {
            cout<<"password input error. Please re-enter again:";
            string thir;
            cin>>thir;
            if(strcmp(thir.c_str(),passwd.c_str())==0)//第三次 
            {
                string newpsw;
                cin>>newpsw;
                passwd=newpsw;
                cout<<"new passwd is set successfully..."<<endl;
            }
            else
            {
                cout<<"password input error. Please try for a while." <<endl;
            }
        }
    }
}
void User::print_info(){
    cout<<"name:\t"<<name<<endl;
    cout<<"passwd:\t"<<"******"<<endl;
    cout<<"email:\t"<<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

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

int main()
{
    using namespace std;

    cout << "testing 1......" << endl;
    User user1("Jane", "113030", "zrh@nuist.com");
    user1.print_info();

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

    User::print_n();
}

• 运行测试结果截图
  • 当修改密码，但是输入旧密码错误时：

 

 

• •  当修改密码，输入旧密码正确时：

 

 

 3、实验总结

• 在编写代码的时候遇到了一些细节方面的问题，现记录如下：
  • 在task4中，验证用户旧密码是否输入正确时，使用到了strcmp函数（头文件<string>），但是忘记了返回值代表的意义。并不是返回ture代表两个字符串匹配，返回false代表两个字符串不匹配。而是：

    return value	indicates
    <0	the first character that does not match has a lower value in ptr1 than in ptr2
    0	the contents of both strings are equal
    >0	the first character that does not match has a greater value in ptr1 than in ptr2

  • 在task4中，用于输出类的属性（static int n）的函数print_n（），在声明的时候必须也加上static关键字（后面定义的时候就不用了），因为静态成员只能由静态函数访问！！！（ps.如果静态函数想访问非静态成员的话可以通过引用对象来实现）