vect.h

// vect.h -- Vector class with <<, mode state
#ifndef VECTOR_H_
#define VECTOR_H_
#include <iostream>
namespace VECTOR
{
    class Vector
    {
    public:
        enum Mode {RECT, POL};
    // RECT for rectangular, POL for Polar modes
    private:
        double x;          // horizontal value
        double y;          // vertical value
        
		// Newly added:remove mag and ang
		// double mag;        // length of vector
        // double ang;        // direction of vector in degrees
        Mode mode;         // RECT or POL
    
		
		// private methods for setting values        
		
		// Newly added: as we use magval() and angval(), and don't store mag and ang
		// therefor no need to keep these 2 data components
		// void set_mag();
        // void set_ang();
        void set_x(double mag, double ang);
        void set_y(double mag, double ang);
    public:
		Vector();       
        Vector(double n1, double n2, Mode form = RECT);
        void reset(double n1, double n2, Mode form = RECT);
        ~Vector();
        double xval() const {return x;}       // report x value
        double yval() const {return y;}       // report y value



		// Newly added: replace mag with its expression
        double magval() const {return sqrt(x * x + y * y);}   // report magnitude
		double angval() const
		{
			if (x == 0.0 && y == 0.0)
				return 0.0;
			else
				return atan2(y, x);
		}// 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);
    };

}   // end namespace VECTOR
#endif
 

vect.cpp

// vect.cpp -- methods for the Vector class
#include <cmath>
#include "vect.h"   // includes <iostream>
using std::sqrt;
using std::sin;
using std::cos;
using std::atan;
using std::atan2;
using std::cout;

namespace VECTOR
{
    // compute degrees in one radian
    const double Rad_to_deg = 45.0 / atan(1.0);
    // should be about 57.2957795130823

    // private methods


    // set x from polar coordinate
	// Newly added:alter,consider replace mag with magval(), ang with angval()
	// but magval() needs x to to calculate,they can't help each other
    void Vector::set_x(double mag,double ang)
    {
        x = mag * cos(ang);
    }

    // set y from polar coordinate
	// Newly added:alter,replay mag with magval(), ang with angval()
	void Vector::set_y(double mag, double ang)
    {
        y = mag * sin(ang);
    }

    // public methods
	// Newly added: remove mag and ang
    Vector::Vector()             // default constructor
    {
        x = y = 0.0;
        mode = RECT;
    }

    // construct vector from rectangular coordinates if form is r
    // (the default) or else from polar coordinates if form is p
    Vector::Vector(double n1, double n2, Mode form)
    {
        mode = form;
        if (form == RECT)
         {
             x = n1;
             y = n2;

			 // Newly added:remove these 2 methods
             // set_mag();
             // set_ang();
        }
        else if (form == POL)
        {
			 // Newly added:remove these 2 variable 
			 // mag = n1;
             // ang = n2 / Rad_to_deg;
			 // inside(),use n1,n2 as mag,ang
             set_x(n1,n2);
             set_y(n1,n2);
        }
        else
        {
             cout << "Incorrect 3rd argument to Vector() -- ";
             cout << "vector set to 0\n";

			 // Newly added:remove these 2 variable
             x = y = 0.0;
             mode = RECT;
        }
    }

    // reset vector from rectangular coordinates if form is
    // RECT (the default) or else from polar coordinates if
    // form is POL
    void Vector:: reset(double n1, double n2, Mode form)
    {
        mode = form;
        if (form == RECT)
         {
             x = n1;
             y = n2;

			 // Newly added:remove these 2 methods
			 // set_mag();
			 // set_ang();
        }
        else if (form == POL)
        {
			 // Newly added:remove these 2 variable 
			 // mag = n1;
             // ang = n2 / Rad_to_deg;
			set_x(n1, n2);
			set_y(n1, n2);
        }
        else
        {
             cout << "Incorrect 3rd argument to Vector() -- ";
             cout << "vector set to 0\n";

			 // Newly added:remove these 2 variable
             x = y = 0.0;
             mode = RECT;
        }
    }

    Vector::~Vector()    // destructor
    {
    }

    void Vector::polar_mode()    // set to polar mode
    {
        mode = POL;
    }

    void Vector::rect_mode()     // set to rectangular mode
    {
        mode = RECT;
    }

    // operator overloading
    // add two Vectors
    Vector Vector::operator+(const Vector & b) const
    {
        return Vector(x + b.x, y + b.y);
    }

    // subtract Vector b from a
    Vector Vector::operator-(const Vector & b) const
    {
        return Vector(x - b.x, y - b.y);
    }

    // reverse sign of Vector
    Vector Vector::operator-() const
    {
        return Vector(-x, -y);
    }

    // multiply vector by n
    Vector Vector::operator*(double n) const
    {
        return Vector(n * x, n * y);
    }

    // friend methods
    // multiply n by Vector a
    Vector operator*(double n, const Vector & a)
    {
        return a * n;
    }

    // display rectangular coordinates if mode is RECT,
    // else display polar coordinates if mode is POL
    std::ostream & operator<<(std::ostream & os, const Vector & v)
    {
        if (v.mode == Vector::RECT)
             os << "(x,y) = (" << v.x << ", " << v.y << ")";
        else if (v.mode == Vector::POL)
        {
             os << "(m,a) = (" << v.magval() << ", "
                 << v.angval() * Rad_to_deg << ")";
        }
        else
             os << "Vector object mode is invalid";
        return os; 
    }

}  // end namespace VECTOR
 

main

// randwalk.cpp -- using the Vector class
// compile with the vect.cpp file
#include <iostream>
#include <cstdlib>      // rand(), srand() prototypes
#include <ctime>        // time() prototype
#include "vect.h"
int main()
{
    using namespace std;
    using VECTOR::Vector;
    srand(time(0));     // seed random-number generator
    double direction;
    Vector step;
    Vector result(0.0, 0.0);
    unsigned long steps = 0;
    double target;
    double dstep;
    cout << "Enter target distance (q to quit): ";
    while (cin >> target)
    {
        cout << "Enter step length: ";
        if (!(cin >> dstep))
            break;

        while (result.magval() < target)
        {
            direction = rand() % 360;
            step.reset(dstep, direction, Vector::POL);
            result = result + step;
            steps++;
        }
        cout << "After " << steps << " steps, the subject "
            "has the following location:\n";
        cout << result << endl;
        result.polar_mode();
        cout << " or\n" << result << endl;
        cout << "Average outward distance per step = "
            << result.magval()/steps << endl;
        steps = 0;
        result.reset(0.0, 0.0);
        cout << "Enter target distance (q to quit): ";
    }
    cout << "Bye!\n";
/* keep window open
    cin.clear();
    while (cin.get() != '\n')
        continue;
    cin.get();
*/
    return 0; 
}