Mercurial > dylan

     1 (ns mtg.frame)

     2 

     3 ;; GENERALLY USEFUL FUNCTIONS

     4 

     5 (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]

     6   (reduce #(if ((first %2) x) (conj %1 (second %2))) '() pred-vals)

     7   )

     8 (defn alter-val "Applies f to the current value associated with each key, associating each key with the value returned." [m f & keys]

     9   (map #(assoc m % (f (get m %))) keys))

    10 

    11 (defn every-nth "Returns every nth member of coll. If n is not positive, returns an empty list." [n coll]

    12   (if (<= n 0) '()

    13   (take-while (comp not nil?) (map first (iterate #(nthnext % n) coll)))))

    14 

    15 

    16 

    17 

    18 

    19 ;; FRAME MANIPULATION

    20 

    21 

    22 (defn conj-key "Adds the xs to the seq associated with the given key." [map key & xs]

    23  (assoc map key (apply conj (get map key []) xs)))

    24 

    25 (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."

    26   [frame & kfs]

    27   (let [id (gensym "up_")

    28 	keys (every-nth 2 kfs)

    29 	fns (every-nth 2 (rest kfs))]

    30 

    31     ((reduce comp (map (fn[k f](fn[m](conj-key m k (list id f) )) keys fns))

    32     (conj-key frame :*bindings* (map (fn [k f](list id k)) keys fns))

    33     )

    34 ))

    35 

    36 

    37 

    38 

    39 (def *frame* (atom {:*bindings* '()}))
author	Robert McIntyre <rlm@mit.edu>
date	Fri, 28 Oct 2011 00:03:05 -0700
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