-- hyperfun for quaternions
-- Author: Frederic Delhoume
-- command: hfp quaternion.hf -g 100 -b 1.8 -d 2 
 
 my_quaternion(x[3], a[1])
 {
 -- replace these values to obtain new objects
     c1 = -1.0;
     c2 = -0.13;
     c3 = 0.0;
     c4 = 0.0;

     bailout = 4.0;
     maxiter = 8;
     lvalue = 0.0;

 -- start of program
     q1 = x[1];
     q2 = x[2];
     q3 = x[3];
     q4 = lvalue;

     bailoutsq = bailout * bailout;
     i = 0;
     while (i < maxiter) loop
	temp = 2.0 * q1;
	q1 = q1^2 - q2^2 - q3^2 - q4^2 + c1;
        q2 = (temp * q2) + c2;
        q3 = (temp * q3) + c3;
        q4 = (temp * q4) + c4;
        length = q1^2 + q2^2 + q3^2 + q4^2;
	if (length > bailoutsq) then
           i = maxiter;
        endif;
        i = i + 1;
     endloop;
 
    my_quaternion =  sqrt(length) - bailout;
 }