Insect operator overloaded a fun

Let's have fun

== Array class ==

== You don't quote back words , You cannot modify the object ==

== Not only can you reduce the number of copies by referring to the parameter , You can also modify objects ==

class Array{public:	Array()	{		for (auto& e : _a)		{			e *= 10;		}			}	// Copy structure print 	Array(Array& a)	{		cout << "Array" << endl;	}	~Array()	{	}	//[] Square bracket dereference is also an operator 	int& operator[](size_t pos)	{		// visit pos Data from that location 		return _a[pos];	}private:	int _a[10] = {0,1,2,3,4,5,6,7,8,9};};int main(){	Array a;	cout << a[0] << endl;	cout << a[1] << endl;	cout << a[2] << endl;	cout << a[3] << endl;	a[0] = 100;	a[1] = 100;	a[2] = 100;	a[3] = 100;	cout << a[0] << endl;	cout << a[1] << endl;	cout << a[2] << endl;	cout << a[3] << endl;	return 0;}

Assignment operator overload

Assignment operators mainly have four points ：

1. Parameter type
2. Return value
3. Check whether you assign values to yourself
4. return *this
5. If a class does not explicitly define an assignment operator overload , The compiler will also generate a , Complete the value copy of objects in byte order .

== Chained assignment copy ==

== But it doesn't rule out that some people assign values to themselves ==

that == The default assignment overloaded function generated by the compiler can already complete the value copy of byte order == 了 , Do we still need to do it ourselves ？

// Date class class  Date{public:	// Constructor does not write , The compiler automatically generates constructors , So the constructor is also the default member function 	Date(int year = 2022, int month = 1, int day = 1)	{		_year = year;		_month = month;		_day = day;	}	// We don't write copy constructs , The compiler will automatically generate a default copy construct 	// Copy structure 	/*Date(const Date& d) { _year = d._year; _month = d._month; _day = d._day; }*/	void Print()	{		cout << _year << "-" << _month << "-" << _day << endl;		}		// Judge whether the dates are equal 	bool operator==(Date x2)	{		return _year == x2._year			&& _month == x2._month			&& _day == x2._day;	}	// Judge whether the left is smaller than the right 	bool operator<(Date x2)	{		if (_year < x2._year)			return true;		else if(_year == x2._year)		{			if (_month < x2._month)				return true;			else if(_month == x2._month)			{				if (_day < x2._day)					return true;			}		}		return false;	}	// Date plus days   The returned date is still 	Date operator+(int day)	{	}	// Date minus days   The returned date is still 	Date operator-(int day)	{	}	// Date minus date   Days returned 	int operator-(Date d2)	{	}	// Copy of assignment  d1 = d1;	Date& operator=(const Date& d)	{		if (this != &d)		{			_year = d._year;			_month = d._month;			_day = d._day;					}		return *this;	}private:	int _year;	int _month;	int _day;};int main(){	Date d1(2022, 1, 1);	Date d2;	Date d3(2022,5,5);	d1.Print();	d2.Print();	d3.Print();	// It's also a copy behavior , But the difference is , Copy construction is when you create an object , Take a copy of the initialization of similar objects 	// Both objects exist when assigning copies here , Are initialized , Now I want to copy the assignment from one object to another 	d1 = d1;	d1 = d2 = d3;	d1.Print();	d2.Print();	d3.Print();	return 0;}

A fun one