Vector模拟随机散步

#include 
#include     // rand(), srand() prototypes
#include       // 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";
    cin.clear();
    while (cin.get() != '\n')
        continue;
    return 0;
}

Enter target distance (q to quit): 50
Enter step length: 2
After 253 steps, the subject has the following location:
(x,y) = (46.1512, 20.4902)
or
(m,a) = (50.495, 23.9402)
Average outward distance per step = 0.199587
Enter target distance (q to quit): 50
Enter step length: 2
After 951 steps, the subject has the following location:
(x,y) = (-21.9577, 45.3019)
or
(m,a) = (50.3429, 115.8593)
Average outward distance per step = 0.0529362
Enter target distance (q to quit): 50
Enter step length: 1
After 1716 steps, the subject has the following location:
(x,y) = (40.0164, 31.1244)
or
(m,a) = (50.6956, 37.8755)
Average outward distance per step = 0.0295429
Enter target distance (q to quit): q
Bye!