#include "mplot.h"void parabola(double x0, double y0, double x1, double y1, double xb, double yb){	register double x, y, t;	double	c0x, c0y, c1x, c1y;	double	dt, d2, d1;	d1 = sqrt((xb - x0) * (xb - x0) + (yb - y0) * (yb - y0));	d2 = sqrt((xb - x1) * (xb - x1) + (yb - y1) * (yb - y1));	if (d1 <= e1->quantum || d2 <= e1->quantum) { 		plotline(x0, y0, x1, y1); 		return; 	}	c0x = x0 + x1 - 2. * xb; 	c1x = 2. * (xb - x0);	c0y = y0 + y1 - 2. * yb; 	c1y = 2. * (yb - y0);	move(x0, y0);	dt = e1->quantum / d1;	dt /= e1->grade;	for (t = dt; t < 0.5; t += dt) {		x = (c0x * t + c1x) * t + x0;		y = (c0y * t + c1y) * t + y0;		vec(x, y);	}	dt = e1->quantum / d2;	dt /= e1->grade;	for (; t < 1.0; t += dt) {		x = (c0x * t + c1x) * t + x0;		y = (c0y * t + c1y) * t + y0;		vec(x, y);	}	vec(x1, y1);}