anchor.diff:  	    (setf x1 (+ x1 (* dt v1))) 
   	    (setf x2 (+ x2 (* dt v2))) 
   	    (setf x3 (+ x3 (* dt v3)))
  +	    (setf ti (+ ti dt))
   	    )))
  -      (with-open-file (stream "traj.txt")
  -	(format stream "~a ~a ~a ~a ~%" (read-line stream)))
  -      (print (list x1 x2 x3)))))
  +      (with-open-file (stream "traj.txt" :direction :output :if-exists :append)
  +	(format stream "~a ~a ~a ~a ~%" ti x1 x2 x3)))))
   
   
  -(loop for i from 0 to 10000 do (integrate 1e-3))
  +(loop for i from 0 to 1000 do (integrate 1e-3))
   
   ;; Time Integration 
   
  
positive.code:       (v1 0.)
        (v2 0.)
        (v3 0.)
        Jt1 Jt2 Jt3 mg1 mg2 mg3 mg rhs)
    (defun integrate (dt)
      (progn
  
negative.code:       (multiple-value-bind  (L U P) (lu (val mg))
  	(let ((x #m((0) (0) (0))))
  	  (progn
  	    (with-open-file (stream "traj.txt" :direction :output :if-exists :append)
  	      (format stream "gravity : ~a ~a ~a ~%" (mref rhs 0 0 ) (mref rhs 1 0 ) (mref rhs 2 0 )))
  	    (solve P L U x rhs)
  	    (setf v1 (+ v1 (* dt (mref x 0 0)))) 
  	    (setf v2 (+ v2 (* dt (mref x 1 0))))
  