parsley-teaser.clj

(def simple-lisp 
  (parser 
    {:main [[:w ? :expr]* :w ?]
     :expr #{:symbol ["("[:w ? :expr]* :w ? ")"]}
     :symbol #"\w+"
     :w #"\s+"}))   

;; helper functions to display results in a more readable way 
(defn terse-result [[items _]]
  (map (fn self [item]
         (if (map? item)
           (cons (:class item) (map self (:contents item)))
           item)) items))

(defn prn-terse [results]
  (doseq [result results]
    (prn (terse-result result))))
    
;; let's parse this snippet
(-> simple-lisp (step "()(hello)") results prn-terse)
;;> ((:main (:expr "()") (:expr "(" (:expr (:symbol "hello")) ")")))

;; let's parse this snippet in two steps
(-> simple-lisp (step "()(hel") (step "lo)") results prn-terse)
;;> ((:main (:expr "()") (:expr "(" (:expr (:symbol "hello")) ")")))

;; and now, the incremental parsing!
(let [c1 (-> simple-lisp reset (step "()(hel"))
      c2 (-> c1 reset (step "lo)" nil))
      _ (-> (stitch c1 c2) results prn-terse) ; business as usual
      c1b (-> simple-lisp reset (step "(bonjour)(hel")) ; an updated 1st chunk
      _ (-> (stitch c1b c2) results prn-terse)] 
  nil)
;;> ((:main (:expr "()") (:expr "(" (:expr (:symbol "hello")) ")")))
;;> ((:main (:expr "(" (:expr (:symbol "bonjour")) ")") (:expr "(" (:expr (:symbol "hello")) ")")))