(defun eulsum (sum term jterm wksp) (declare (type double-float sum))
 (declare (type double-float term)) (declare (type fixnum jterm))
 (declare (type (simple-array double-float (*)) wksp))
 (prog ((dum 0.0d0) (j 0) (tmp 0.0d0) (nterm 0))
  (declare (type double-float dum)) (declare (type fixnum j))
  (declare (type double-float tmp)) (declare (type fixnum nterm))
  (cond
   ((= jterm 1) (setf nterm 1) (fset (fref wksp 1) term)
    (setf sum (* 0.5 term))
   )
   (t (setf tmp (fref wksp 1)) (fset (fref wksp 1) term)
    (fdo ((j 1 (+ j 1))) ((> j nterm) nil)
     (tagbody (setf dum (fref wksp (+ j 1)))
      (fset (fref wksp (+ j 1)) (* 0.5 (+ (fref wksp j) tmp))) (setf tmp dum)
    ))
    (cond
     ((<= (abs (fref wksp (+ nterm 1))) (abs (fref wksp nterm)))
      (setf sum (+ sum (* 0.5 (fref wksp (+ nterm 1)))))
      (setf nterm (+ nterm 1))
     )
     (t (setf sum (+ sum (fref wksp (+ nterm 1)))))
  )))
  (return (values sum term jterm wksp))
))