anchor.diff:        (v1 0.)
         (v2 0.)
         (v3 0.)
  +      (ti 0.0)
         Jt1 Jt2 Jt3 mg1 mg2 mg3 mg rhs)
     (defun integrate (dt)
       (progn
  
positive.code: 	    (setf x1 (+ x1 (* dt v1))) 
  	    (setf x2 (+ x2 (* dt v2))) 
  	    (setf x3 (+ x3 (* dt v3)))
  	    )))
        (with-open-file (stream "traj.txt")
  	(format stream "~a ~a ~a ~a ~%" (read-line stream)))
        (print (list x1 x2 x3)))))
  
  
  (loop for i from 0 to 10000 do (integrate 1e-3))
  
  ;; Time Integration 
  
  
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))))
  