C++Primer Plus第十一章类的使用，课后练习1，还是醉汉回家的故事

编程练习11.9
1.修改程序清单 11.5，使之将一系列连续的随机漫步者位置写入到文件中。对于每个位置，用步号进行标示。另外，让该程序将初始条件(目标距离和步长)以及结果小结写入到该文件中。该文件的内容与下面类似:
Target Distance:100，stepSize:20
0:(xy)=(0，0)
1:(x,y)=(-11.4715，16.383)
2:(x,y)=(-8.68807，-3.42232)
26:(x,y)=(42.2919，-78.2594)
27:(x,y)=(58.6749，-89.7309)
After 27 steps,the subject has the following location:
(x,y)=(58.6749，-89.7309)
or
(m,a)=(107.212，-56.8194)
Average outward distance perstep=3.97081

vector.h

#pragma once
//vect.h -- Vector class with <<,mode state
#ifndef	VECTOR_H_	
#define VECTOR_H_

#include<iostream>
namespace VECTOR
{
   
	class Vector
	{
   
	public:
		enum Mode {
    RECT, POL };//以此为直角坐标，极坐标（长度，角度）
		//RECT for rectangular,POL for Polar modes
	private:
		double x;//horizontal value x方向x坐标
		double y;//vertical value  y方向y坐标
		double mag; //length of value  极坐标的长度
		double ang;//direction of vector in degrees，极坐标的角度
		Mode mode;//RECT or POL
		//private methods for setting values
		void set_mag();
		void set_ang();
		void set_x();
		void set_y();
	public:
		Vector();
		Vector(double x, double y, Mode form = RECT);
		void reset(double x, double y, Mode form = RECT);
		~Vector();
		double xval()const {
    return x; }//report x val
		double yval()const {
    return y; }//report y val
		double magVal()const {
    return mag; }//report magnitude
		double angval()const {
    return ang; }//report angle
		void polar_mode();//set mode to POL
		void rect_mode();//set mode to RECT
		//operator overloading 
		Vector operator+(const Vector& b)const;
		Vector operator-(const Vector& b)const;
		Vector operator-()const;
		Vector operator*(double n)const;
		//friends
		friend Vector operator*(double n, const Vector& a);
		friend std::ostream& operator<<(std::ostream& os, const Vector& v)