(ns rlm.clojure-example)

 

 (defn curry

   "takes a function with a fixed number of args and modifies

    it to that it will be automaticaly curried when called with

    less args"

   ([num-args f & eval-list]

      (if (= num-args (count eval-list))

        (apply f eval-list)

        (fn [& args]

 	 (apply curry num-args f (concat eval-list args))))))

 

 (defn mix 

   "Takes any number of mathematically equal functions with

    possibly different run-times and returns a function that

    runs each in a separate thread, returns the result from

    the first thread which finishes, and cancels the other threads."

   {:author "Robert McIntyre"}

   ([& functions]

      (fn [& args]

        (let [result (promise)

 	     futures

 	     (doall (for [fun functions]

 		      (future (deliver result (apply fun args)))))

 	     answer @result]

 	 (dorun (map future-cancel futures))

 	 answer))))

 

 (defn memoize*

   "Returns a memoized version of a referentially transparent

   function. The memoized version of the function keeps a cache of the

   mapping from argument 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"}

   [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)))))

 

 ;;immutable data structures

 (def r {:a :a :b :b})

 (def b (assoc r :c :c))

 

 (defn collapse [coll & head]

   (if (= (count coll) 0)

     (first head)

     (let [x (first coll)]

       (if (list? x)

 	(collapse (concat x (rest coll)) (first head))

 	(collapse (rest coll) (conj (vec (first head)) x))))))

 ;;email clojure group about this

 

 

 (defn collapse* [coll]

   (loop [head [] body coll]

     (let [x (first body)]

       (cond (= (count body) 0) head

 	    (list? x) (recur head (concat x (next body)))

 	    true      (recur (conj head x) (next body))))))