c++primer plus练习10，练习6重复练习，这个思维要改正过来

6.下面是一个类声明:
class Move
{
private:
double x;
double y;
public:
Move(doublea = 0，doubleb = 0);//sets x,yto a,b
showmove()const;
//shows currentx，yvalues
Move add(const Move& m)const;
//this function adds xof m to x of invoking object to get new x
// adds yof m to yof invoking object to get new y,creates a new
//move object initialized to new x,y values and returns it
reset(double a = 0, doubleb = 0);//resets x,y to a,b
};

class Move
{
private:
	double x;
	double y;
public:
	Move(double a = 0,double b = 0);
	void showmove()const;
	Move add(const Move& m)const;
	void reset(double a = 0, double b = 0);
};

#include<iostream>
#include"pe10-6.h"
Move::Move(double a, double b){
	this->x = a;
	this->y = b;
}
void
Move::showmove()const{
	std::cout << "x,y = " << this->x<<", " << this->y;
}

Move Move::add(const Move& m)const{
	return Move((x+m.x),(y+m.y));
}
void
Move::reset(double a, double b){
	this->x = a, this->y = b;
}

#include <iostream>
#include"pe10-6.h"
/*
*/
using std::cout;
using std::endl;
int main()
{
	//using namespace std;
	Move move1(3,4);
	move1.showmove();
	cout << endl;
	Move move2(12, 13);
	move2.showmove();
	cout << endl;
	move1.add(move2).showmove();
	cout << endl;
	move1.reset();
	move1.showmove();

	cout << endl;
	return 0;
}

打印输出的结果，在函数add中一定要给上数据类型，不然会转换失败

Move Move::add(const Move& m)const{
	return Move((x+m.x),(y+m.y));
}