(defmacro nlet (tag var-vals &body body)
  `(labels ((,tag ,(mapcar #'car var-vals) ,@body))
     (,tag ,@(mapcar #'cadr var-vals))))

(defun iota (n)
  (nlet loop ((i 0))
    (if (>= i n) '()
      (cons i (loop (+ i 1))))))