rlm@2: (ns mtg.frame)
rlm@2: 
rlm@2: ;; GENERALLY USEFUL FUNCTIONS
rlm@2: 
rlm@2: (defn assay "Takes x and a series of pred-value pairs. Returns a list of vals for which the corresponding preds are true of x." [x & pred-vals]
rlm@2:   (reduce #(if ((first %2) x) (conj %1 (second %2))) '() pred-vals)
rlm@2:   )
rlm@2: (defn alter-val "Applies f to the current value associated with each key, associating each key with the value returned." [m f & keys]
rlm@2:   (map #(assoc m % (f (get m %))) keys))
rlm@2: 
rlm@2: (defn every-nth "Returns every nth member of coll. If n is not positive, returns an empty list." [n coll]
rlm@2:   (if (<= n 0) '()
rlm@2:   (take-while (comp not nil?) (map first (iterate #(nthnext % n) coll)))))
rlm@2: 
rlm@2: 
rlm@2: 
rlm@2: 
rlm@2: 
rlm@2: ;; FRAME MANIPULATION
rlm@2: 
rlm@2: (defn conj-key "Adds the xs to the seq associated with the given key." [map key & xs]
rlm@2:  (assoc map key (apply conj (get map key []) xs)))
rlm@2: 
rlm@2: (defn update "Takes a frame and a sequence of key-fn pairs. Applies f to the current value associated with key, updating the current value with the result.  Frames generate and store a unique id for each call to update."
rlm@2:   [frame & kfs]
rlm@2:   (let [id (gensym "")
rlm@2: 	keys (every-nth 2 kfs)
rlm@2: 	fns (every-nth 2 (rest kfs))]
rlm@2: 
rlm@2:     ((reduce comp (map (fn[k f](fn[m](conj-key m k (list id f)))) keys fns))
rlm@2:     (conj-key frame :*bindings* (map (fn [k f](list id k)) keys fns))
rlm@2:     )
rlm@2: ))
rlm@2: 
rlm@2: (defn rollback "Undo the update with the given id." [frame id]
rlm@2:   (let [affected-keys
rlm@2: 	(conj (map second (filter #(=(first %) id) (:*bindings* frame))) :*bindings*)]
rlm@2:     (reduce (fn[frame key]
rlm@2: 	      (alter-val (partial filter #(=(first %) id)) key)
rlm@2: 	      ) frame affected-keys)
rlm@2:   ))
rlm@2: 
rlm@2: 
rlm@2: (defn get-fn "Keys in a frame store lists of modifiers. Produces the end result of applying all the modifiers in order." [frame key]
rlm@2:     (reduce #(%2) (constantly nil) (list (constantly 1)))
rlm@2: )
rlm@2: 
rlm@2: 
rlm@2: (def *frame* (atom {:*bindings* '()}))
rlm@2: