实验二——类与对象（2）

task2:array<int,5> x3<x1>;语句在devc的环境下可能会报错，改成array<int,5> x3（x1）可正确编译。

task3:to_string的功能是将数字常量转换为字符串，还有就是要注意，静态变量类外初始化，并且要注意初始化时没有static。

task4:

#pragma once
#include<iostream>
#include<cmath>
using namespace std;
class Complex{
    public:
    Complex (double x=0.0,double y=0.0 );
     Complex(const Complex &c);
    double get_real() const;
    double get_imag() const;
    void show() const;
    void add(Complex c1);
    friend Complex add(Complex c1,Complex c2);
    friend bool is_equal(Complex c1,Complex c2);
    friend double abs(Complex c);
    private:
        double real;
        double imag;    
};

Complex::Complex(double x,double y) :real(x),imag(y){}
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::add(Complex c1){real=real+c1.real;imag=imag+c1.imag;}
void Complex::show() const {if(imag>0)cout<<real<<"+"<<imag<<"i";else if(imag<0) cout<<real<<imag<<"i";else cout<<real;}
Complex add(Complex c1,Complex c2){Complex c3;c3.real=c1.real+c2.real;c3.imag=c1.imag+c2.imag;return c3;}
bool is_equal(Complex c1,Complex c2){if(c1.real==c2.real&&c1.imag==c2.imag) return true ;else return false;}
double abs(Complex c){double s=sqrt(c.real*c.real+c.imag*c.imag); return s;}
    
    
    

#include "Complex.h"
#include <iostream>
void test() {
    using namespace std;

    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;
}

int main() {
    test();
}

出现的问题：实验四的.cpp文件中用const定义了一个对象c2，所以c2.show（）必须也是const，因为c2这个对象是无权访问非const成员函数的。并且，构造函数是不能通过const进行重载的！

task5：

#ifndef ABCD_H
 #define ABCD_H
#include<iostream>
#include<string>
using namespace std;
class User{
    public:
    User (string name0,string passwd1="111111",string email1="\0");
    User(const User&u) :name{ u.name }, passwd{ u.passwd }, email{ u.email }{
        User::n++;}
     ~User();
void set_email();
void change_passwd();
 void print_info();
 static void printf_n(){cout<<"there are"<<User::n<<"usrs"<<endl;
}
    private :
        string name;
        string passwd;
        string email;
        static  int n;
};
int User::n=0;
User::User(string name0,string passwd1,string email1):name{name0},passwd{passwd1},email(email1){User::n++;}

User::~User(){User::n--;} 
void User::set_email(){email="\0";cout<<"enter email adress:"; cin>>email;cout<<"email is set successfully..."<<endl;}
void User::change_passwd(){ int i=0,flag=0;
cout<<"enter old passwd"<<endl;
string p1;
cin>>p1;
for(i=0;i<=2;i++)
{
if(p1!=passwd)
{
cout<<"send error,please write again";
cin>>p1;}
else 
{
string p2;
cout<<"enter new password:";
cin>>p2;
passwd=p2;
cout<<"new password is set successfully"<<endl;
flag=1;
break;}}
if(flag==0)
cout<<"please try after a while"<<endl;
}
void User::print_info()
{int i=0;
    cout<<"name"<<name<<endl;

    for(i=0;i<passwd.size();i++)
    cout<<"*";
    cout<<"email:"<<email<<endl;
}


//cin不能有endl 
//字符串的赋值 
#endif

task5.cpp:
#include "User.h"

#include <iostream>
void test() {
    using std::cout;
    using std::endl;

    cout << "testing 1......\n";
    User user1("Jonny", "92197", "[email protected]");
    user1.print_info();

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

    cout << endl;
    User::printf_n();
}

int main() {
    test();
}

task5存在的问题：cin输入里不能有endl控制符，会报错。还有就是对string字符串类型的赋值要注意