9.7 괄호 연산자 오버로딩 하기

#include <iostream>
using namespace std;

class Accumulator
{
private:
    int m_counter = 0;
public:
    int operator()(int i) { return (m_counter += i ); }
};

int main(){
  
    Accumulator acc;
    cout << acc(10) << "\n";
    cout << acc(20) << "\n";
    return 0;
}