(ql:quickload :petalisp)
(defun bbp (k)
  (declare (fixnum k))
  (/ (- (/ 4 (+ (* 8 k) 1))
        (/ 2 (+ (* 8 k) 4))
        (/ 1 (+ (* 8 k) 5))
        (/ 1 (+ (* 8 k) 6)))
     (expt 16 k)))
(defvar *pi-size* (ceiling (integer-length (expt 10 10000)) 4)
  "The number of hexadecimal digits we want to calculate Pi to")
(defvar *pi*
  (petalisp:beta #'+
                 (petalisp:alpha #'bbp
                                 (coerce (loop for x from 0 to *pi-size* collect x)
                                         'vector))))
(defun write-ratio (ratio length)
  (dotimes (n length)
    (write-char (digit-char (floor (mod ratio 10))))
    (setf ratio (* ratio 10))
    (when (zerop (mod n 10))
      (fresh-line))))

(time (write-ratio (petalisp:compute *pi*) 10000))