Clojure

Clojure

Êëàññ ÿçûêà:	ôóíêöèîíàëüíûé, ìóëüòèïàðàäèãìàëüíûé
Ïîÿâèëñÿ â:	2007
Àâòîð(û):	Ðè÷ Õèêêè
Ðåëèç:	1.4 (15 àïðåëÿ 2012)
Òèïèçàöèÿ äàííûõ:	äèíàìè÷åñêàÿ, ñòðîãàÿ
Èñïûòàë âëèÿíèå:	Lisp, ML, Haskell, Erlang
Ëèöåíçèÿ	Eclipse Public License
Ñàéò:	http://clojure.org

Clojure (ïðîèçíîñèòñÿ êàê closure) â ýòî ñîâðåìåííûé äèàëåêò Ëèñïà. Ýòî ÿçûê ïðîãðàììèðîâàíèÿ îáùåãî íàçíà÷åíèÿ ñ ïîääåðæêîé ðàçðàáîòêè â èíòåðàêòèâíîì ðåæèìå, ïîîùðÿþùèé ôóíêöèîíàëüíîå ïðîãðàììèðîâàíèå, è óïðîùàþùèé ïîääåðæêó ìíîãîïîòî÷íîñòè. Clojure ðàáîòàåò íà ïëàòôîðìàõ JVM è CLR. Clojure îòëè÷àåò ôèëîñîôèÿ «êîä êàê äàííûå (àíãë.)» è ðàçâèòàÿ ñèñòåìà ëèñï-ìàêðîñîâ.

Òðàíñëÿòîð Clojure ñâîáîäíî ðàñïðîñòðàíÿåòñÿ íà óñëîâèÿõ Eclipse Public License.

Ôèëîñîôèÿ

Ðè÷ Õèêêè ðàçðàáîòàë Clojure êàê ñîâðåìåííûé Ëèñï äëÿ ôóíêöèîíàëüíîãî ïðîãðàììèðîâàíèÿ ñ èíòåãðàöèåé â Java ïëàòôîðìó, ñïðîåêòèðîâàííûé äëÿ ïîääåðæêè êîíêóðåíòíûõ âû÷èñëåíèé.

Ñèíòàêñèñ

Êàê è â ëþáîì äðóãîì Ëèñïå, ñèíòàêñèñ Clojure îñíîâàí íà S-âûðàæåíèÿõ, êîòîðûå ïåðåä êîìïèëÿöèåé òðàíñëèðóþòñÿ ñèíòàêñè÷åñêèì àíàëèçàòîðîì â ñòðóêòóðû äàííûõ. Ñèíòàêñè÷åñêèé àíàëèçàòîð Clojure ïîääåðæèâàåò, ïîìèìî îáû÷íûõ ñïèñêîâ, ñèíòàêñèñ ëèòåðàëîâ äëÿ àññîöèàòèâíûõ ìàññèâîâ, ìíîæåñòâ è âåêòîðîâ, ïåðåäàâàÿ çàòåì âñå ýòè ñòðóêòóðû äàííûõ êîìïèëÿòîðó. Èíà÷å ãîâîðÿ, êîìïèëÿòîð Clojure êîìïèëèðóåò íå òîëüêî ñïèñêîâûå ñòðóêòóðû äàííûõ, íî íàïðÿìóþ ïîääåðæèâàåò âñå óêàçàííûå òèïû. Clojure ÿâëÿåòñÿ ðàñøèðåíèåì èçíà÷àëüíîé âåðñèè Lisp, è íå ïðåäíàçíà÷åí äëÿ êîäà ñîâìåñòèìîãî ñ äðóãèìè äèàëåêòàìè Ëèñïà.

Ìàêðîñû

Ìàêðî ñèñòåìà Clojure î÷åíü ïîõîæà íà àíàëîãè÷íóþ ñèñòåìó Common Lisp, çà òåì èñêëþ÷åíèåì ÷òî èñïîëüçóåìûé â Clojure âàðèàíò îáðàòíîé êàâû÷êè (òàê íàçûâàåìûé «ñèíòàêñèñ öèòèðîâàíèÿ») êâàëèôèöèðóåò ñèìâîëû èõ èìåíåì. Ýòî ïîìîãàåò ïðåäîòâðàòèòü íåïðåäíàìåðåííûé çàõâàò èìåíè ïðè ïðèâÿçêå ê ïðîñòðàíñòâó èì¸í â êâàëèôèêàöèÿ èì¸í çàïðåùåíà. Ìîæíî âûïîëíèòü òàêîé çàõâàò ïðè ìàêðîïîäñòàíîâêå, íî ýòî äîëæíî áûòü ñäåëàíî ÿâíî. Clojure òàêæå çàïðåùàåò ñâÿçûâàíèå ãëîáàëüíûõ èì¸í èç äðóãèõ ïðîñòðàíñòâ èì¸í, êîòîðûå áûëè èìïîðòèðîâàíû â òåêóùåå ïðîñòðàíñòâå èì¸í.

Îñîáåííîñòè ÿçûêà

• Äèíàìè÷åñêàÿ, èíòåðàêòèâíàÿ ðàçðàáîòêà â REPL-öèêëå
• Ôóíêöèè êàê îáúåêòû ïåðâîãî êëàññà ñ àêöåíòîì íà ðåêóðñèþ, à íå íà îñíîâàííóþ íà ïîáî÷íûõ ýôôåêòàõ èòåðàöèþ
• «Ëåíèâûå» ïîñëåäîâàòåëüíîñòè
• Îáåñïå÷èâàåò áîãàòûé íàáîð íåèçìåíÿåìûõ, ñîõðàíÿåìûõ ñòðóêòóð äàííûõ (àíãë.)
• ïàðàëëåëüíîå ïðîãðàììèðîâàíèå ñ ïîääåðæêîé òðàíçàêöèîííîé ïàìÿòè, àãåíòíîé ñèñòåìû è ñèñòåìû äèíàìè÷åñêèõ ïåðåìåííûõ
• Clojure êîìïèëèðóåìûé ÿçûê, ðåçóëüòàòîì êîìïèëÿöèè ÿâëÿåòñÿ áàéòêîä JVM
• Òåñíàÿ èíòåãðàöèÿ ñ Java: çà ñ÷¸ò êîìïèëÿöèè â áàéòêîä JVM ïðîãðàììû íà Clojure ëåãêî ïåðåíîñÿòñÿ â ëþáóþ ñðåäó ñ JVM. ßçûê òàêæå îáåñïå÷èâàåò ðÿä ìàêðîñîâ, êîòîðûå óïðîùàþò èñïîëüçîâàíèå â í¸ì ñóùåñòâóþùèõ Java API. Ñòðóêòóðû äàííûõ Clojure ðåàëèçóþò âñå ñòàíäàðòíûå èíòåðôåéñû Java, ÷òî äåëàåò ëåãêèì çàïóñê èç Java ïðîãðàììíîãî êîäà íàïèñàííîãî íà Clojure.

Ïðèìåðû

Hello world:

(println "Çäðàâñòâóé, ìèð!")

Ïîòîêîáåçîïàñíûé ãåíåðàòîð óíèêàëüíûõ ñåðèéíûõ íîìåðîâ:

(let [i (atom 0)]
  (defn generate-unique-id
    "Âîçâðàùàåò ðàçëè÷íûå ÷èñëîâûå ID äëÿ êàæäîãî âûçîâà."
    []
    (swap! i inc)))

Àíîíèìíûé ïîäêëàññ java.io.Writer êîòîðûé íè÷åãî íå âûâîäèò, è ìàêðîñ èñïîëüçóåìûé, ÷òîáû çàãëóøèòü âåñü âûâîä âíóòðè íåãî:

(def bit-bucket-writer
  (proxy [java.io.Writer] []
    (write [buf] nil)
    (close []    nil)
    (flush []    nil)))
 
(defmacro noprint
  "Âû÷èñëÿåò çàäàííûå âûðàæåíèÿ, çàãëóøàÿ âåñü *âûâîä* íà ýêðàí".
  [& forms]
  `(binding [*out* bit-bucket-writer]
     ~@forms))
 
(noprint
 (println "Hello, nobody!"))

10 ïîòîêîâ, ìàíèïóëèðóþùèõ îäíîé îáùåé ñòðóêòóðîé äàííûõ, êîòîðàÿ ñîñòîèò èç 100 âåêòîðîâ, êàæäûé èç êîòîðûõ ñîäåðæèò 10 (èçíà÷àëüíî ïîñëåäîâàòåëüíûõ) óíèêàëüíûõ ÷èñåë. Êàæäûé ïîòîê ìíîãîêðàòíî âûáèðàåò äâå ñëó÷àéíûõ ïîçèöèè â äâóõ ñëó÷àéíûõ âåêòîðàõ è îáìåíèâàåò ìåñòàìè èõ çíà÷åíèÿ. Âñå èçìåíåíèÿ âåêòîðîâ ïðîèñõîäÿò â åäèíîé òðàíçàêöèè ïóòåì èñïîëüçîâàíèÿ ñèñòåìû òðàíçàêöèîííîé ïàìÿòè clojure. Ïîýòîìó äàæå ïîñëå 1000 èòåðàöèé â êàæäîì èç ïîòîêîâ ÷èñëà íå òåðÿþòñÿ.

(defn run [nvecs nitems nthreads niters]
  (let [vec-refs (vec (map (comp ref vec)
                           (partition nitems (range (* nvecs nitems)))))
        swap #(let [v1 (rand-int nvecs)
                    v2 (rand-int nvecs)
                    i1 (rand-int nitems)
                    i2 (rand-int nitems)]
                (dosync
                 (let [temp (nth @(vec-refs v1) i1)]
                   (alter (vec-refs v1) assoc i1 (nth @(vec-refs v2) i2))
                   (alter (vec-refs v2) assoc i2 temp))))
        report #(do
                 (prn (map deref vec-refs))
                 (println "Distinct:"
                          (count (distinct (apply concat (map deref vec-refs))))))]
    (report)
    (dorun (apply pcalls (repeat nthreads #(dotimes [_ niters] (swap)))))
    (report)))
 
(run 100 10 10 100000)

Âûâîä ïðåäûäóùåãî ïðèìåðà:

([0 1 2 3 4 5 6 7 8 9] [10 11 12 13 14 15 16 17 18 19] ...
 [990 991 992 993 994 995 996 997 998 999])
Distinct: 1000
 
([382 318 466 963 619 22 21 273 45 596] [808 639 804 471 394 904 952 75 289 778] ...
 [484 216 622 139 651 592 379 228 242 355])
Distinct: 1000

Áèáëèîãðàôèÿ

• Halloway, Stuart (May 28, 2009), Programming Clojure (1st ed.), Pragmatic Bookshelf, pp. 304, ISBN 1934356336, <http://pragprog.com/titles/shcloj/programming-clojure> 
• VanderHart, Luke (June 7, 2010), Practical Clojure (1st ed.), Apress, pp. 350, ISBN 1430272317, <http://www.apress.com/book/view/9781430272311> 
• Rathore, Amit (Early 2011), Clojure in Action (1st ed.), Manning, pp. 475, ISBN 9781935182597, <http://www.manning.com/rathore/> 
• Fogus, Michael & Houser, Chris (December, 2010), The Joy of Clojure (1st ed.), Manning, pp. 300, ISBN 9781935182641, <http://www.manning.com/fogus/> 

Ññûëêè

• îôèöèàëüíûé ñàéò Clojure  (àíãë.)
• ðåïîçèòîðèé êîäà Clojure íà GitHub (àíãë.)
• Clojure â Functional Programming for the JVM (àíãë.) â ïîäðîáíûé îáçîð ÿçûêà
• Full Disclojure â Âèäåîäåìîíñòðàöèÿ (àíãë.)

Íà ðóññêîì ÿçûêå

• ßçûê ïðîãðàììèðîâàíèÿ Clojure â Ââåäåíèå íà IBM developerWorks
• Àëåêñ Îòò. Clojure, èëè «Âû âñå åù¸ èñïîëüçóåòå Java? Òîãäà ìû èäåì ê âàì!» â 4 âûïóñêå æóðíàëà «Ïðàêòèêà ôóíêöèîíàëüíîãî ïðîãðàììèðîâàíèÿ» (Îáíîâëåííàÿ âåðñèÿ ñòàòüè, ñ îïèñàíèåì âåðñèè 1.2)
• Ôîðóì î Clojure íà lisper.ru
• ru_clojure â ñîîáùåñòâî «Clojure» â Æèâîì Æóðíàëå
• Ðóññêàÿ ïëàíåòà Clojure â àããðåãàòîð ðóññêîÿçû÷íûõ áëîãîâ î Clojure