// PROGRAM wheel

#include "TrueBASIC.h"
int main();
void initial(double *r, double *omega, double *vcm, double *t, double *dt, 
             double *xmax);

int main()
{
    double dt, omega, r, t, vcm, x = 0, xmax, y;

    GWopen(0);

    initial(&r, &omega, &vcm, &t, &dt, &xmax);
    GWsetpen(-1, -1, -1, -1);
    while(x <= xmax)
    {
        x = -r*cos(omega*t) + vcm*t;
        y = r*sin(omega*t);
        GWline2((float)(x), (float)(y));
        t += dt;
    }

    GWquit();
    return 0;
}

void initial(double *r, double *omega, double *vcm, double *t, double *dt, 
             double *xmax)
{
    float mx, xmin;

    (*t) = 0;
    (*r) = 1;                               // 車輪の半径
    (*omega) = 1;                           // 車輪の角速度
    (*vcm) = (*r)*(*omega);                 // 質量中心の速度
    (*dt) = 0.01;                           // 時間の増分
    xmin = -1;
    (*xmax) = 50;
    mx = 0.01*((*xmax) - xmin);
    GWindow(xmin-mx, -4.0f, (float)((*xmax)+mx), 4.0f);
    // y = -r (車輪の最下部) の位置に地面を描く
    GWline(xmin, (float)(-(*r)), (float)((*xmax)), (float)(-(*r)));
}