integer_sqrt.cl

; code translated from
; https://en.wikipedia.org/wiki/Integer_square_root
; note that theirs actually has an off by one error
(defun integer-sqrt (n)
  (prog ((shift 2) (result 0))
        (declare (fixnum n shift result))

        (if (< n 2) (return n))
        shifting
        (if (not (= (ash n (- shift)) 0))
            (progn  
              (incf shift)
              (incf shift)
              (go shifting)  
              ))

        unroll
        (setf result (ash result 1))
        (let ((larger (+ result 1)))
          (declare (fixnum larger))
          (if (<= (* larger larger) (ash n (- shift)))
              (setf result larger)
              )
          (decf shift)
          (decf shift)
          )
        (if (>= shift 0)
            (go unroll)
            )
        (return result)
        ))