;; First we define a function that presumably have some expensive computation. user=> (defn myfunc[a] (println "doing some work") (+ a 10)) #'user/myfunc ;; Next we create a memoized version of the function. user=> (def myfunc-memo (memoize myfunc)) #'user/myfunc-memo ;; The first time we call the function with a particular argument the ;; original function is invoked and the value is returned. The next ;; time the function is called with the same argument the cached result ;; is returned and the original function is NOT called. user=> (myfunc-memo 1) doing some work 11 user=> (myfunc-memo 1) 11 user=> (myfunc-memo 20) doing some work 30 user=> (myfunc-memo 20) 30
Source
clojure/core.clj:5579
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(defn memoize
"Returns a memoized version of a referentially transparent function. The
memoized version of the function keeps a cache of the mapping from arguments
to results and, when calls with the same arguments are repeated often, has
higher performance at the expense of higher memory use."
{:added "1.0"
:static true}
[f]
(let [mem (atom {})]
(fn [& args]
(if-let [e (find @mem args)]
(val e)
(let [ret (apply f args)]
(swap! mem assoc args ret)
ret)))))
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