10.20

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#include<complex.h>
#include<iostream>
#include<cmath>

int main()
{
    using namespace std;
    
    complex<double> c1(3,4);
    complex<double> c2(4.5);
    complex<double> c3(c2);
    
    cout << " c1 = " << c1 << endl;
    cout << " c2 = " << c2 << endl;
    cout << " c3 = " << c3 << endl;
    
    cout << " c1 + c2 = " << c1 + c2 << endl;
    
    cout << boolalpha;//设置布偶型bool值以true/false方式输出
    cout << " c1 == c2 : " << (c1 == c2 ) << endl;
    cout << "c3 == c2 : " << (c3 == c2 ) << endl;
    
    cout << "abs(c1) = " << abs(c1) << endl;//abs()对复数进行取模运算，头文件cmath
    complex<int> c4(3,4),c5(2,7);
    
    cout << "c4 - c5 = " << c4 - c5 << endl;      
}

#ifndef EMPLOYEE_HPP
#define EMPLOYEE_HPP

// Employee类的定义
#include <iostream>
#include <iomanip>
#include <string>

using namespace std;

struct Date
{
    int year;
    int month;
    int day;
};

// Employee类的声明
class Employee
{
public:
    Employee();
    Employee(string name0, double salary0, int y, int m, int d);
    void set_info(string name0, double salary0, int y, int m, int d); // 设置雇员信息
    string get_name() const;      // 获取雇员姓名
    double get_salary() const;    // 获取雇员薪水
    void display_info() const;    // 显示雇员信息
    void update_salary(double s);  // 更新雇员薪水
    void update_hire_date(int y, int m, int d); // 更新雇佣日期
    void raise_salary(double by_percent);  // 
    static void display_count();
private:
    string name;   // 雇员姓名
    double salary; // 雇员薪水
    Date hire_date;  // 雇员雇佣日期
    static int count;   // 用于记录雇员总人数
};

int Employee::count = 0;

// 默认构造函数
Employee::Employee()
{
    ++count;
}

// 带参数的构造函数
Employee::Employee(string name0, double salary0, int y, int m, int d): name{name0}, salary{salary0}, hire_date{y, m, d}
{  
    ++count;
}

// 设置员工信息
void Employee::set_info(string name0, double salary0, int y, int m, int d)
{
    name = name0;
    salary = salary0;
    hire_date.year = y;
    hire_date.month = m;
    hire_date.day = d;
}

// 获取员工姓名
string Employee::get_name() const
{
    return name;
}

// 获取员工薪水
double Employee::get_salary() const
{
    return salary;
}

// 显示雇员信息
void Employee::display_info() const
{
    cout << "name: " << name << endl;
    cout << "salary: " << salary << endl;
    cout << "hire_date: " << hire_date.year << "-" << setfill('0') << setw(2) << hire_date.month << "-" 
                                                                   << setw(2) << hire_date.day;
}

// 更新薪水
void Employee::update_salary(double s) 
{
    salary = s;
}

// 更新雇佣日期
void Employee::update_hire_date(int y, int m, int d)
{
    hire_date.year = y;
    hire_date.month = m;
    hire_date.day = d;
}

// 雇员提薪加成
// by_percent是提升比例
void Employee::raise_salary(double by_percent)
{
    double raise = salary * by_percent / 100;
    salary += raise;
}

// 显示雇员总数
void Employee::display_count()
{
    cout << "there are " << count << " employees\n";
}

#endif

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

int main()
{
    using namespace std;

    Employee employee1;
    employee1.set_info("Sam", 30000, 2015, 1, 6);
    employee1.update_hire_date(2017, 6, 30);
    employee1.update_salary(35000);
    employee1.display_info();
    cout << endl << endl;

    Employee employee2("Tony", 20000, 2020, 3, 16);
    employee2.raise_salary(15);
    employee2.display_info();
    cout << endl << endl;

    Employee::display_count();
}

#include<iostream>
#include<cmath>

using namespace std;

class Complex
{
public:
    Complex(int x = 0, int y = 0 );//不能在一个类里面同时声明一个默认构造器，和一个带有默认参数的构造函数； 
    //构造函数不能被申明为const; 
    Complex(const Complex &c);
    
    int get_real() ;
    int get_imag() const;
    void show() const;//因为c2为const所以如果在这里不声明为const就会放大c2的权限 
    void add(Complex c) ;

private:
    int real;
    int imag;
    
    friend Complex add(const Complex c1,const Complex c2);
    friend bool is_equal(const Complex c1,const Complex c2);//友元函数不能被声明为const因为它不属于类里面的东西
    //所以当友元函数和构造函数的参数为const时，形参需要被定义为const； 
    friend int abs(const Complex c);
};
//
Complex::Complex(int x, int y  ) //声明中构造函数同时声明缺省参数，而在构造函数的定义中不用再次声明缺省参数。 
{
    real = x;
    imag = y;
}

Complex::Complex(const Complex &c)
{
    real = c.real;
    imag = c.imag;
}

int Complex::get_real() 
{
    return real;
}
 
int Complex::get_imag() const
{
    return  imag;
}

void Complex::show() const
{
    cout << real << imag << "i" << endl;
}

void Complex::add(Complex c) 
{
    real += c.real;
    imag += c.imag;
}

Complex add(const Complex c1,const Complex c2)
{
    Complex a;
    a.real = c1.real + c2.real;
    a.imag = c1.imag + c2.imag;
    return a;
}

bool is_equal(const Complex c1,const Complex c2)
{
    if( (c1.real == c2.real) && (c1.imag == c2.imag))
    {
        return true;
    }
    
    return false;
}

int abs(const Complex c) 
{
    int a;
    a = sqrt( ( c.real) * (c.real) + (c.imag) * (c.imag));
    return a;
    
}

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

int main()
{
    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;
    
    return 0;
}

#include<iostream>
#include<string>

using namespace std;

class User
{
public:
    User(string theName, string thePassword = "111111",string theEmail = "");
    void set_email();
    void change_passwd();
    void print_info();
    static void print_n() ;

private:
    string name;
    string password;
    string email;
    static int count;
};



User::User(string theName, string thePassword,string theEmail)
{
    name = theName;
    password = thePassword;
    email = theEmail;
    count++;
}

void User::set_email()
{
    cout << " Enter email address:";
    cin >> email;
    cout << "email is set succesfully\n";
}

void User::change_passwd()
{
    string input; 
    cout << "Enter old password:";
    cin >> input;
    int n = 2;
    while((n != 0) && (input != password))
    {
        n--; 
        cout << "password input error. Please re-enter again:";
        cin >> input;
    }
    
    if(input == password)
    {
        cout << "Enter new password:";
        cin >> password;
        cout << "new passwd is set successful..." << endl; 
    }
    
    if(n == 0)
    {
        cout<< "Please try after a while" << endl;
    }
}
 
void User::print_info()
{
    cout << "name: " << name << endl;
    cout << "passed: ******\n";
    cout << "email: " << email << endl;
     
}

void User::print_n() 
{
    cout << "there are " << count << "uesr.\n"; 
}

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

int User::count = 0;//count是静态成员，为其分配空间需要在主函数的文件内，主函数前进行 
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();
}

实验总结:

1.不能在一个类里面同时声明一个默认构造器，和一个带有默认参数的构造函数；

2.构造函数不能被申明为const,友元函数不能被声明为const因为它不属于类里面的东西，所以当友元函数和构造函数的参数为const时，形参需要被定义为const；

3.因为c2为const所以如果类的函数不声明为const就会放大c2的权限 

4.声明中构造函数同时声明缺省参数，而在构造函数的定义中不用再次声明缺省参数。

5.为静态成员分配内存要在主函数的文件内

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