0cpp

C++ primer plus第六版课后编程题答案11.1(已修改)

 

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该题之前有bug,不知道是当时复制错了还是怎么样，现已修改。如下:

mvector.h

 

#ifndef mVector_H_
#define mVector_H_
#include <iostream>
#include <cmath>
using namespace std;
static const double Rad_to_deg=45.0/atan(1.0);
class mVector
{
    public:
      enum Mode{RECT,POL};
    private:
        double x;
        double y;
        double mag;
        double ang;
        Mode mode;

        void set_mag(){
            mag=sqrt(x*x+y*y);
        };

        void set_ang(){
            if(x==0.0&&y==0.0)
                ang=0.0;
            else
                ang=atan2(y,x);
        };
        void set_x(){
            x=mag*cos(ang);
        };
        void set_y(){
            y=mag*sin(ang);
        };
        //from here
       //static const double Rad_to_deg=45.0/atan(1.0);
    public:
        mVector(){
         x=y=mag=ang=0.0;
         mode=RECT;
        };

        mVector(double n1,double n2,Mode form=RECT){
            mode=form;
            if(form==RECT)
            {
                x=n1;
                y=n2;
                set_mag();
                set_ang();
            }
            else if(form==POL)
            {
                mag=n1;
                ang=n2;
                set_x();
                set_y();
            }
            else
            {
                cout<<"Incorrect 3rd argument to mVector()--";
                cout<<"mVector set to 0\n";
                x=y=mag=0.0;
                mode=RECT;
            }
        };
        ~mVector(){
        };

        void reset(double n1,double n2,Mode form=RECT){
            mode=form;
            if(form==RECT)
            {
                x=n1;
                y=n2;
                set_mag();
                set_ang();
            }
            else if(form==POL)
            {
                mag=n1;
                ang=n2;
                set_x();
                set_y();
            }
            else
            {
                cout<<"Incorrect 3rd argument to mVector()--";
                cout<<"mVector set to 0\n";
                x=y=mag=0.0;
                mode=RECT;
            }
        };
        double xval()const{return x;};
        double yval()const{return y;};
        double magval()const {return mag;};
        double angval()const {return ang;};

        void polar_mode(){
            mode=POL;
        };
        void rect_mode(){
            mode=RECT;
        };

        mVector operator+(const mVector &b)const{
         return mVector(x+b.x,y+b.y);
        };
        mVector operator-(const mVector &b)const{
            return mVector(x-b.x,y-b.y);
        };
        mVector operator-()const{
            return mVector(-x,-y);
        };
        mVector operator*(double n)const{
            return mVector(n*x,n*y);
        };
        void show(ofstream &os){
          //ofstream os;
		if(mode==mVector::RECT)//必须用Vector::
			os<<"(x,y)=("<<x<<","<<y<<")";
		else if(mode==mVector::POL)
			os<<"(m,a)=("<<mag<<","<<ang<<")";
  	 };	//add it

        friend mVector operator*(double n,const mVector &b){
          return b*n;
        };
        //friend ostream & operator<<(ostream &os,const mVector &v);
        friend ofstream & operator<<(ofstream &fs,const mVector &v){//写到文件
            if(v.mode==mVector::RECT)//必须用Vector::
                fs<<"(x,y)=("<<v.x<<","<<v.y<<")";
            else if(v.mode==mVector::POL)
            {
                fs<<"(m,a)=("<<v.mag<<","<<v.ang*Rad_to_deg<<")";
            }
            else
                fs<<"mVector object mode is invalid!";
            return fs;
        }

    };
#endif

m.cpp

 

#include <iostream>
#include <fstream>
#include <cstdio>
#include <cstdlib>
#include <ctime>
//#include <mVector>
#include "mvector.h"
using namespace std;
int main(int argc,char **argv)
{
    ofstream fin;
    fin.open("111.txt");//打开文件
    if(fin.fail())
        cout<<"open fali!"<<endl;
    //else
        //cout<<"Sucess!"<<endl;
    //fin<<"111";
    srand(time(0));
    double direction;
	mVector step;
	mVector result(0.0,0.0);
    unsigned long steps=0;
    double target;//要走的距离
    double dstep;//每一步的距离
    cout<<"Enter target step length:(q to quit:)";
    while(cin>>target)
    {
        cout<<"Enter dstep length:";
        if(!(cin>>dstep))
            break;
        int i=0;	//上面的少了这个
        while(result.magval()<target)
        {
        		fin<<"\n"<<i++<<"  ";
				result.show(fin);//2
            direction=rand()%360;
            step.reset(dstep,direction,mVector::mVector::POL);
            result=result+step;
            steps++;
        }
        cout<<endl<<"After "<<steps<<" steps ,the subject "
            <<" has the following location:"<<endl;
        fin<<"After "<<steps<<" steps ,the subject "
            <<" has the following location:"<<endl;
        fin<<result;
        result.polar_mode();
        //cout<<" or \n"<<result<<endl;
        fin<<" or \n";
        fin<<result<<endl;
        cout<<"Average outward distance per step="
            <<result.magval()/steps<<endl;
        fin<<"Average outward distance per step="
            <<result.magval()/steps<<endl;
        steps=0;
        result.reset(0.0,0.0);
        cout<<"Enter target distance (q to quit):";

    }
    fin<<"Bye!\n";
    cin.clear();
    while(cin.get()!='\n')
        continue;
    //cin.get();
    fin.close();
}

运行结果：

111.txt的内容：

 

0  (x,y)=(0,0)
1  (x,y)=(4.81299,1.35467)
2  (x,y)=(1.41287,5.02063)
3  (x,y)=(-3.42338,6.28974)
4  (x,y)=(-2.09017,11.1087)
5  (x,y)=(-4.09009,6.52611)
6  (x,y)=(0.221501,3.99428)
7  (x,y)=(4.72083,6.17511)
8  (x,y)=(9.25807,8.27594)
9  (x,y)=(5.92338,12.0015)
10  (x,y)=(6.21089,7.00978)
11  (x,y)=(3.65988,11.3101)
12  (x,y)=(-0.629139,13.8799)
13  (x,y)=(-4.3101,10.4961)
14  (x,y)=(-2.6812,15.2233)
15  (x,y)=(1.81814,17.4041)
16  (x,y)=(5.75671,14.3239)
17  (x,y)=(7.59331,9.67346)
18  (x,y)=(12.5651,10.2035)
19  (x,y)=(7.6596,9.23618)
20  (x,y)=(5.03286,13.4906)
21  (x,y)=(4.30536,18.4374)
22  (x,y)=(7.47196,22.3069)After 23 steps ,the subject  has the following location:
(x,y)=(12.3501,23.4041) or 
(m,a)=(26.4628,62.1799)
Average outward distance per step=1.15055
Bye!

截图：

感谢网友v_empire的指出。
谢谢!

//写的错误或者不好的地方请多多指导，可以在下面留言或者点击左上方邮件地址给我发邮件，指出我的错误以及不足，以便我修改，更好的分享给大家，谢谢。

转载请注明出处：http://blog.csdn.net/qq844352155

author:天下无双

Email:coderguang@gmail.com

2014-9-22

于GDUT

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下面的是错误的，仅做保留，请勿参考！

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vector.h

<span style="font-size:18px;">#ifndef VECTOR_H_
#define VECTOR_H_
#include <iostream>
using namespace std;
namespace VECTOR
{
	class Vector
	{
	public:
	  enum Mode{RECT,POL};
	private:
		double x;
		double y;
		double mag;
		double ang;
		Mode mode;
		
		void set_mag();
		void set_ang();
		void set_x();
		void set_y();
	public:
		Vector();

		Vector(double n1,double n2,Mode form=RECT);
		~Vector();

		void reset(double n1,double n2,Mode form=RECT);

		double xval()const{return x;};
		double yval()const{return y;};
		double magval()const {return mag;};
		double angval()const {return ang;};
		
		void polar_mode();
		void rect_mode();

		Vector operator+(const Vector &b)const;
		Vector operator-(const Vector &b)const;
		Vector operator-()const;
		Vector operator*(double n)const;

		friend Vector operator*(double n,const Vector &b);
		//friend ostream & operator<<(ostream &os,const Vector &v);
		friend ofstream & operator<<(ofstream &fs,const Vector &v);//写到文件
		

	
	};

}
#endif </span>


vector.h

<span style="font-size:18px;">/*我去啊，我不过是为了简单一点直接写在h文件里面，用不用这么多错误啊*/
#include <iostream>
#include <cmath>
#include "vector.h"
#include <fstream>
using  std::cout;
using std::sin;
using std::sqrt;
using std::cos;
using std::atan;
using std::atan2;
using namespace VECTOR;
namespace VECTOR{

	const double Rad_to_deg=45.0/atan(1.0);
	void Vector::set_mag(){
		mag=sqrt(x*x+y*y);
		};
	void Vector::set_ang(){
			if(x==0.0&&y==0.0)
				ang=0.0;
			else
				ang=atan2(y,x);
		};
	
		void Vector::set_x(){
			x=mag*cos(ang);
		};
		void Vector::set_y(){
			y=mag*sin(ang);
		};

		Vector::Vector(){
		 x=y=mag=ang=0.0;
		 mode=RECT;
		};
		//
		Vector::Vector(double n1,double n2,Mode form){
			mode=form;
			if(form==RECT)
			{
				x=n1;
				y=n2;
				set_mag();
				set_ang();
			}
			else if(form==POL)
			{
				mag=n1;
				ang=n2;
				set_x();
				set_y();
			}
			else
			{
				cout<<"Incorrect 3rd argument to Vector()--";
				cout<<"Vector set to 0\n";
				x=y=mag=0.0;
				mode=RECT;
			}
		};
		Vector::~Vector(){};

		void Vector::reset(double n1,double n2,Mode form)
		{
			mode=form;
			if(form==RECT)
			{
				x=n1;
				y=n2;
				set_mag();
				set_ang();
			}
			else if(form==POL)
			{
				mag=n1;
				ang=n2;
				set_x();
				set_y();
			}
			else
			{
				cout<<"Incorrect 3rd argument to Vector()--";
				cout<<"Vector set to 0\n";
				x=y=mag=0.0;
				mode=RECT;
			}
		};
		/*
		double Vector::xval()const{return x;};
		double Vector::yval()const{return y;};
		double Vector::magval()const {return mag;};
		double Vector::angval()const {return ang;};
		*/
		void Vector::polar_mode(){mode=POL;};
		void Vector::rect_mode(){mode=RECT;};

		Vector Vector::operator+(const Vector &b)const{
		 return Vector(x+b.x,y+b.y);
		};
		Vector Vector::operator-(const Vector &b)const {
			return Vector(x-b.x,y-b.y);
		};
		Vector Vector::operator-()const{
			return Vector(-x,-y);
		}
		Vector Vector::operator*(double n)const{
			return Vector(n*x,n*y);
		};

		Vector operator*(double n,const Vector &b){
		  return b*n;
		};
		/*
		std::ostream & operator<<(std::ostream &os,const Vector &v)
		{
			if(v.mode==Vector::RECT)//必须用Vector::
				os<<"(x,y)=("<<v.x<<","<<v.y<<")";
			else if(v.mode==Vector::POL)
			{
				os<<"(m,a)=("<<v.mag<<","<<v.ang*Rad_to_deg<<")";
			}
			else
				os<<"Vector object mode is invalid!";
			return os;
		}
		*/
		std::ofstream & operator<<(std::ofstream &fs,const Vector &v)
		{
			if(v.mode==Vector::RECT)//必须用Vector::
				fs<<"(x,y)=("<<v.x<<","<<v.y<<")";
			else if(v.mode==Vector::POL)
			{
				fs<<"(m,a)=("<<v.mag<<","<<v.ang*Rad_to_deg<<")";
			}
			else
				fs<<"Vector object mode is invalid!";
			return fs;
		}<span style="font-family: Arial, Helvetica, sans-serif;">	void show(ofstream &os)</span>
<span style="white-space:pre">		</span>{
<span style="white-space:pre">			</span>//ofstream os;
<span style="white-space:pre">			</span>if(mode==Vector::RECT)//必须用Vector::
<span style="white-space:pre">				</span>os<<"(x,y)=("<<x<<","<<y<<")";
<span style="white-space:pre">			</span>else if(mode==Vector::POL)
<span style="white-space:pre">			</span>{
<span style="white-space:pre">				</span>os<<"(m,a)=("<<mag<<","<<ang<<")";
<span style="white-space:pre">			</span>}
<span style="white-space:pre">			</span>
<span style="white-space:pre">		</span>};</span>
	
}
</span>


main111.cpp

<span style="font-size:18px;">#include <iostream>
#include <fstream>
#include <cstdio>
#include <ctime>
//#include <vector>
#include "vector.h"
using namespace std;
using  namespace VECTOR;
void main111()
{
	ofstream fin;
	fin.open("111.txt");//打开文件
	if(fin.fail())
		cout<<"open fali!"<<endl;
	//else 
		//cout<<"Sucess!"<<endl;
	//fin<<"111";
	srand(time(0));
	double direction;
	Vector step;
	Vector result(0.0,0.0);
	unsigned long steps=0;
	double target;//要走的距离
	double dstep;//每一步的距离
	cout<<"Enter step length:(q to quit:)";
	while(cin>>target)
	{
		cout<<"Enter step length:";
		if(!(cin>>dstep))
			break;
		while(result.magval()<target)
		{</span>
<span style="font-size:18px;"><span style="white-space:pre">			fin<<"\n"<<i++<<"  ";
<span style="white-space:pre">			</span>result.show(fin);//2</span>
			direction=rand()%360;
			step.reset(dstep,direction,Vector::POL);
			result=result+step;
			steps++;
		}
		cout<<"After "<<steps<<" steps ,the subject "
			<<" has the following location:"<<endl;
		fin<<"After "<<steps<<" steps ,the subject "
			<<" has the following location:"<<endl;
		fin<<result;
		result.polar_mode();
		//cout<<" or \n"<<result<<endl;
		fin<<" or \n";
		fin<<result<<endl;
		cout<<"Average outward distance per step="
			<<result.magval()/steps<<endl;
		fin<<"Average outward distance per step="
			<<result.magval()/steps<<endl;
		steps=0;
		result.reset(0.0,0.0);
		cout<<"Enter target distance (q to quit):";
	
	}
	fin<<"Bye!\n";
	cin.clear();
	while(cin.get()!='\n')
		continue;
	//cin.get();





	fin.close();


}</span>

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//写的错误或者不好的地方请多多指导，可以在下面留言或者给我发邮件，指出我的错误以及不足，以便我修改，更好的分享给大家，谢谢。

转载请注明出处：https://www.royalchen.com/

author:royalchen

Email:royalchen@royalchen.com

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royalchen

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