I've been reading a bit about the STM, and here's an implementation of a
FIFO cache for producing a memoized version of a function. Is it correct to
use the STM in this case, or are there any drawbacks?
(defn bounded-memoize
"Return a bounded memoized version of fn 'f'
that caches the last 'k' computed values"
[f k]
(let [cache (ref {})
values (ref clojure.lang.PersistentQueue/EMPTY)]
(fn [& args]
(if-let [e (find @cache args)]
(val e)
(let [result (apply f args)]
(dosync
(alter values conj args)
(alter cache assoc args result)
(if (> (count @values) k)
(let [evict (peek @values)]
(alter values pop)
(alter cache dissoc evict))
)
result
))
)
))
)
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