readers from grammars

reader.clj

(defn lazy-reader [start prods]
  (let [step (vm/stepper (asm/link (grammar start prods)))]
    (fn self
      ([input] (self input (vector-tree-builder input)))
      ([input builder]
        ((fn f [state i]
           (lazy-seq
             (when (< i (count input))
               (let [state (step state i (nth input i))]
                 (if (when-let [stacks (get state -2)]
                       (zero? (-> stacks :carry (:error 0))))
                   (cons (builder (reduce builder (builder) (:events (:carry (get state -2)))))
                     (f (step) (inc i)))
                 (f state (inc i)))))))
          (step) 0)))))
          
=> (let [r (lazy-reader :root lang)]
      (r "(todo)[todo]"))
([[:list "(" [:symbol "todo"] ")"]] [[:vector "(todo)[" [:symbol "todo"] "]"]])
=> (count *1)
2
=> (let [r (lazy-reader :root lang)]
      (r "(todo)  [todo]"))
([[:list "(" [:symbol "todo"] ")"]] [[:whitespace "(todo)  "] [:vector "[" [:symbol "todo"] "]"]])
=> (count *1)
2