#define incx() x++, dxt += d2xt, t += dxt
#define incy() y--, dyt += d2yt, t += dyt

void ellipse(int xc, int yc, int rx, int ry, int color)
{
    int x = 0, y = ry;
    long rx2 = (long)rx*rx, ry2 = (long)ry*ry;
    long crit1 = -(rx2/4 + rx%2 + ry2);
    long crit2 = -(ry2/4 + ry%2 + rx2);
    long crit3 = -(ry2/4 + ry%2);
    long t = -rx2*y; // e(x+1/2,y-1/2) - (a^2+b^2)/4
    long dxt = 2*ry2*x, dyt = -2*rx2*y;
    long d2xt = 2*ry2, d2yt = 2*rx2;

    while (y>=0 && x<=rx)
    {
        pixel(xc+x, yc+y, color);
        if (x!=0 || y!=0)
            pixel(xc-x, yc-y, color);
        if (x!=0 && y!=0)
        {
            pixel(xc+x, yc-y, color);
            pixel(xc-x, yc+y, color);
        }
        if (t + ry2*x <= crit1 ||   //e(x+1,y-1/2) <= 0
            t + rx2*y <= crit3)     //e(x+1/2,y) <= 0
            incx();
        else if (t - rx2*y > crit2) //e(x+1/2,y-1) > 0
            incy();
        else
        {
            incx();
            incy();
        }
    }
}

#define incx() do { x++; dxt += d2xt; t += dxt; } while (0)
#define incy() do { y--; dyt += d2yt; t += dyt; } while (0)

cpp cpp.c > cppout.c

# 1 "cpp.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "cpp.c"



void ellipse(int xc, int yc, int rx, int ry, int color)
{
    int x = 0, y = ry;
    long rx2 = (long)rx*rx, ry2 = (long)ry*ry;
    long crit1 = -(rx2/4 + rx%2 + ry2);
    long crit2 = -(ry2/4 + ry%2 + rx2);
    long crit3 = -(ry2/4 + ry%2);
    long t = -rx2*y;
    long dxt = 2*ry2*x, dyt = -2*rx2*y;
    long d2xt = 2*ry2, d2yt = 2*rx2;

    while (y>=0 && x<=rx)
    {
        pixel(xc+x, yc+y, color);
        if (x!=0 || y!=0)
            pixel(xc-x, yc-y, color);
        if (x!=0 && y!=0)
        {
            pixel(xc+x, yc-y, color);
            pixel(xc-x, yc+y, color);
        }
        if (t + ry2*x <= crit1 ||
            t + rx2*y <= crit3)
            x++, dxt += d2xt, t += dxt;
        else if (t - rx2*y > crit2)
            y--, dyt += d2yt, t += dyt;
        else
        {
            x++, dxt += d2xt, t += dxt;
            y--, dyt += d2yt, t += dyt;
        }
    }
}

if (t + ry2*x <= crit1 ||
        t + rx2*y <= crit3) {

        x++;
        dxt += d2xt;
        t += dxt;

    } else if (t - rx2*y > crit2) {
        y--;
        dyt += d2yt;
        t += dyt;

    } else {
        x++;
        dxt += d2xt;
        t += dxt;

        y--;
        dyt += d2yt;
        t += dyt;
    }

#define incx() x++, dxt += d2xt, t += dxt

if (t + ry2*x <= crit1 || t + rx2*y <= crit3)
    incx();

if (t + ry2*x <= crit1 || t + rx2*y <= crit3)
    x++, dxt += d2xt, t += dxt;

void ellipse(int xc, int yc, int rx, int ry, int color)
{
    int x = 0, y = ry;
    long rx2 = (long)rx*rx, ry2 = (long)ry*ry;
    long crit1 = -(rx2/4 + rx%2 + ry2);
    long crit2 = -(ry2/4 + ry%2 + rx2);
    long crit3 = -(ry2/4 + ry%2);
    long t = -rx2*y; // e(x+1/2,y-1/2) - (a^2+b^2)/4
    long dxt = 2*ry2*x, dyt = -2*rx2*y;
    long d2xt = 2*ry2, d2yt = 2*rx2;

    while (y>=0 && x<=rx)
    {
        pixel(xc+x, yc+y, color);
        if (x!=0 || y!=0)
            pixel(xc-x, yc-y, color);
        if (x!=0 && y!=0)
        {
            pixel(xc+x, yc-y, color);
            pixel(xc-x, yc+y, color);
        }
        if (t + ry2*x <= crit1 ||   //e(x+1,y-1/2) <= 0
            t + rx2*y <= crit3)     //e(x+1/2,y) <= 0
            x++, dxt += d2xt, t += dxt;
        else if (t - rx2*y > crit2) //e(x+1/2,y-1) > 0
            y--, dyt += d2yt, t += dyt;
        else
        {
            x++, dxt += d2xt, t += dxt;
            y--, dyt += d2yt, t += dyt;
        }
    }
}