Cyclic tag system in Clojure

gta

; t a list of productions, a an initial sequence
; note this halts with a NPE - it should really 
; check for (empty? a) and reduced

(defn g [t a]
  (reductions 
    (fn [[g & t] a] 
      (if (== 1 g) (concat t a) t)) 
    a (cycle t)))
    
(take 32 (g [[0 1 1] [1 1 1]] [1]))