C++ 연산자 오버로딩 - 사용자 정의 리터럴

#include <iostream>
#include <chrono>

using namespace std;

class Length {
private:
	const long double _value;
	Length(long double value) : _value(value) {

	}

	friend Length operator"" _m(unsigned long long int value);
	friend Length operator"" _m(long double value);
	friend Length operator"" _km(unsigned long long int value);
	friend Length operator"" _km(long double value);

public:
	long double m() const {
		return _value;
	}
	long double km() const {
		return _value * 0.001;
	}
	Length operator-() const {
		return Length(-_value);
	}
	Length operator+(const Length& length) const {
		return Length(_value + length._value);
	}
};

Length operator"" _m(unsigned long long int value) {
	return Length(value);
}
// ""는 공백없이 바로 앞에 숫자를 붙이는 것을 의미
Length operator"" _m(long double value) {
	return Length(value);
}

Length operator"" _km(unsigned long long int value) {
	return Length(1000 * value);
}

Length operator"" _km(long double value) {
	return Length(1000 * value);
}

int main() {
	chrono::minutes m = 1h + 5min;

	Length len = 1_m + 2_km;
	cout << len.m() << "m" << endl;
	cout << len.km() << "km" << endl;

	cout << m.count() << endl;
}

• 실행 결과

  2001m
  2.001km
  65