(def = args
  (if (no (cdr args))  t
      (some atom args) (all [id _ (car args)] (cdr args))
                       (and (apply = (map car args))
                            (apply = (map cdr args)))))

(def symbol (x) (= (type x) 'symbol))

(def pair   (x) (= (type x) 'pair))

(def char   (x) (= (type x) 'char))

(def stream (x) (= (type x) 'stream))

(def proper (x)
  (or (no x)
      (and (pair x) (proper (cdr x)))))

(def string (x)
  (and (proper x) (all char x)))