C++實驗一 類與對象

一、實驗結論

1.實驗任務3

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

int main()
{
    using namespace std;

    Complex c1(5, -3);
    const Complex c2(2.8);
    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;
}      

#ifndef COMPLEX_HPP
#define COMPLEX_HPP

#include <iostream>
#include <cmath>

class Complex{
    public:
        Complex():real(0),imag(0){}
        Complex(double r,double i=0){
            real=r;
            imag=i;
        }
        Complex(const Complex  &c){
            real=c.real;
            imag=c.imag;
        }
        
        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(Complex &c1);
        ~Complex(){}
        
    private:
        double real,imag;
};

double Complex::get_real() const{
    return real;
}
double Complex::get_imag() const{
    return imag;
}
void Complex::show() const{
    using namespace std;
    if (imag>0)
        cout << real << " + " << imag << "i";
    else if (imag<0)
        cout << real << " - " << -imag << "i";
    else 
        cout << real;
}
void Complex::add(const Complex &c){
    real=real+c.get_real();
    imag=imag+c.get_imag(); 
} 

Complex add(const Complex &c1,const Complex &c2){
    Complex c(c1.real+c2.real,c1.imag+c2.imag);
    return c;
} 
bool is_equal(const Complex &c1,const Complex &c2){
    if(c1.real==c2.real && c1.imag==c2.imag){
        return true;
    }else return false;
}
double abs(Complex &c){
    return sqrt(c.real*c.real+c.imag*c.imag);
}

#endif      

2.實驗任務4

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

int main()
{
    using namespace std;

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

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

    User::print_n();
}      

#ifndef USER_HPP
#define USER_HPP

#include <iostream>
#include <string>

using namespace std;
class User{
    public:
        User(string nn,string p="111111",string e=""){
            name = nn;
            passwd = p;
            email = e;
            n++;
        }
        void set_email();
        void change_passwd();
        void print_info();
        static void print_n(){
            cout << "there are " << n << " users" <<endl;
        }
    private:
        string name;
        string passwd;
        string email;
        static int n;
}; 

void User::set_email(){
    string a;
    cout << "Please input e_mail:";
    cin >> a;
    if(a.find('@')!=string::npos){
        cout << "Set e_mail success!" << endl;
        email = a;
    }else {
        cout << "e_mail is illegal!" << endl;
    }
}
void User::change_passwd(){
    cout << "Please input your past password:";
    int flag=0;
    for (int i=0;i<3;i++){
        string a;
        cin >> a;
        if(a==passwd){
            flag=1;
            break;
        }else if(i<2){
            cout << "Error!Please re_input your past password:";
        }
    }
    if(flag){
        cout << "Passwd right!Please input your new password:";
        cin >> passwd;
        cout << "Change success!" << endl;
    }else {
        cout << "Error!This window will close" <<endl;
    }
}
void User:: print_info(){
    cout << "name: " << name <<endl;
    cout << "passwd: " << "******" << endl;
    cout << "email: " << email <<endl;
}

int User::n = 0; 

#endif       

二、實驗總結

1.string的相關操作中，find() 函數傳回符合搜尋條件的字元區間内的第一個字元的索引，沒有找到目标就傳回npos ，npos類似于size_type;