C++) 연산자 오버로딩

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홍정모의 따라하며 배우는 C++ - 인프런 | 강의

산술 연산자 오버로딩

#include <iostream>
using namespace std;

class Cents
{
private:
	int _cents;
public:
	Cents(int cents) { _cents = cents; }
	int getCents() const { return _cents; }
	Cents operator + (const Cents& c2)
	{
		return Cents(this->_cents + c2._cents);
	}
	Cents operator * (const Cents& c2)
	{
		return Cents(this->_cents * c2._cents);
	}
};

int main()
{
	Cents cents1(6);
	Cents cents2(8);

	cout << (cents1 + cents2 * Cents(5)).getCents() << endl;	// 6 + 8 * 5 = 46

	return 0;
}

 

입출력 연산자 오버로딩

#include <iostream>
#include<fstream>
using namespace std;

class Point
{
private:
	double _x, _y, _z;

public:
	Point(double x = 0.0, double y = 0.0, double z = 0.0)
		: _x(x), _y(y), _z(z)
	{}

	double getX() { return _x; }
	double getY() { return _y; }
	double getZ() { return _z; }

	// 첫번째 parameter가 ostream이라 member function으로 만들 수 없다
	friend ostream& operator << (ostream& out, const Point& point)
	{
		out << "(" << point._x << " " << point._y << " " << point._z << ")";
		return out;
	}

	friend istream& operator >> (istream& in, Point& point)
	{
		in >> point._x >> point._y >> point._z;
		return in;
	}

};

int main()
{
	ofstream of("out.txt");

	//Point p1(0.1, 0.2, 0.3), p2(0.4, 1.1, 2.3);
	Point p1, p2;

	cin >> p1 >> p2;

	cout << p1 << " " << p2 << endl;
	of << p1 << " " << p2 << endl;

	of.close();

	return 0;
}

 

단항 연산자 오버로딩

// 단항 연산자 오버로딩
#include <iostream>
using namespace std;

class Cents
{
private:
	int _cents;

public: 
	Cents(int cents = 0) { _cents = cents; }
	int getCents() const { return _cents; }
	int& getCents() { return _cents; }

	Cents operator - () const
	{
		return Cents(-_cents);
	}

	bool operator ! () const
	{
		return (_cents == 0 ) ? true : false;
	}

	friend ostream& operator << (ostream& out, const Cents& cents)
	{
		out << cents._cents;
		return out;
	}
};

int main()
{
	Cents cents1(6);
	Cents cents2(0);

	int a = 3;

	cout << -cents1 << " " << cents2 << endl;	// -6 0
	cout << !cents1 << " " << !cents2 << endl;	// 0 1

	return 0;
}

 

비교 연산자 오버로딩

#include <iostream>
#include <vector>
#include <algorithm>
#include <random>
using namespace std;

class Cents
{
private:
	int _cents;

public:
	Cents(int cents = 0) { _cents = cents; }
	int getCents() const { return _cents; }
	int& getCents() { return _cents; }

	bool operator < (const Cents& s2)
	{
		return this->_cents < s2._cents;
	}

	bool operator == (const Cents& s2)
	{
		return this->_cents == s2._cents;
	}

	friend ostream& operator << (ostream& out, const Cents& cents)
	{
		out << cents._cents;
		return out;
	}
};

int main()
{
	Cents s1(1), s2(1);

	if (s1 == s2) cout << "Equal" << endl;

	vector<Cents> arr(20);
	for (unsigned i = 0; i < 20; ++i)
		arr[i].getCents() = i;

	random_device rd;
	mt19937 g(rd());
	shuffle(begin(arr), end(arr),g);	// C++17

	for (auto& e : arr)
		cout << e << " ";
	cout << endl;

	sort(begin(arr), end(arr));

	for (auto& e : arr)
		cout << e << " ";
	cout << endl;

	return 0;
}

 

증감 연산자 오버로딩

#include <iostream>
using namespace std;

class Digit
{
private:
	int _digit;

public:
	Digit(int digit = 0) : _digit(digit)
	{}

	// prefix
	Digit& operator ++ ()
	{
		++_digit;
		return *this;
	}

	// postfix
	Digit operator ++ (int)
	{
		Digit temp(_digit);

		++(*this);

		return temp;
	}

	friend ostream& operator << (ostream& out, const Digit& d)
	{
		out << d._digit;
		return out;
	}
};

int main()
{
	int a = 10;
	cout << ++a << endl;	// 11
	cout << a << endl;	// 11
	cout << a++ << endl;	// 11
	cout << a << endl;	// 12

	Digit d(5);

	cout << ++d << endl;	// 6

	cout << d++ << endl;	// 6
	cout << d << endl;	// 7

	return 0;
}

 

첨자 연산자 오버로딩

#include <iostream>
#include<cassert>
using namespace std;

class IntList
{
private:
	int _list[10] = {1,2,3,4,5,6,7,8,9,10};

public:

	int& operator [] (const int index)
	{
		assert(index >= 0);
		assert(index < 10);

		return _list[index];
	}

	const int& operator [] (const int index) const
	{
		assert(index >= 0);
		assert(index < 10);

		return _list[index];
	}

	void setItem(int index, int value)
	{
		_list[index] = value;
	}

	int getItem(int index)
	{
		return _list[index];
	}

	int* getList()
	{
		return _list;
	}
};

int main()
{
	IntList my_list;
	my_list[3] = 10;
	cout << my_list[3] << endl;
	

	return 0;
}

 

괄호 연산자 오버로딩

#include <iostream>
using namespace std;

class Accumulator
{
private:
	int _counter = 0;

public:
	int operator () (int i) { return (_counter += i); }
};

int main()
{
	Accumulator acc;

	cout << acc(10) << endl;
	cout << acc(20) << endl;

	return 0;
}

 

형변환 오버로딩

#include <iostream>
using namespace std;

class Cents
{
private:
	int _cents;

public:
	Cents(int cents = 0)
	{
		_cents = cents;
	}

	int getCents() { return _cents; }
	void setCents(int cents) { _cents = cents; }

	operator int()
	{
		cout << "cast here" << endl;
		return _cents;
	}
};

class Dollar
{
private:
	int _dollars = 0;

public:
	Dollar(const int& input): _dollars(input) {}

	operator Cents()
	{
		return Cents(_dollars * 100);
	}
};

void printInt(const int& value)
{
	cout << value << endl;
}

int main()
{
	Cents cents(7);

	int value = (int)cents;
	printInt(value);
	printInt(cents);

	printInt((Cents) Dollar(5));

	return 0;
}