#include<iostream>usingnamespacestd;classSquare{public:doubleoperator()(doublex)const{returnx*x;}intoperator()(inta,intb,intc=0)const{returna+b-c;}};intmain(void){Squaresq;//括号里面的参数会被自动当作形参传入cout<<sq(12)<<endl;//144cout<<sq(1,5,3)<<endl;//3cout<<sq(1,3)<<endl;//4return0;}