Introduction to Clojure

Transcript

1. Introduction to Clojure Pablo Tamarit October 30, 2012 GenevaJUG
2. ? 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 1999 - 2005 EIG 2007 - 2049 CERN
3. (def basket [{:name "apples", :type :fruits} {:name "pears", :type :fruits} {:name "scoubidous", :type :objects}]) (group-by :type basket) {:fruits [{:type :fruits, :name "apples"} {:type :fruits, :name "pears"}], :objects [{:type :objects, :name "scoubidous"}]} Sampling 
4. • Philosophical part • Theoretical part • Practical part
5. Philosophical part
6. Clojure • Created in 2007 • Simplicity • Not object oriented! • Dynamic typing • Everything is immutable • No state • No side effects • Dialect of Lisp! + λ
7. Lisp • Invented in 1958
8. John McCarthy 1927 – 2011
9. Lisp • Invented in 1958 • Lots of Irritating Superfluous Parentheses?
10. Lisp • Invented in 1958 • Lots of Irritating Superfluous Parentheses • Homoiconicity • Macros paulgraham.com/avg.html
11. Theoretical part
12. Language • Simple syntax, rich vocabulary. – Syntax: data, functions – Vocabulary: functions clojure.org/cheatsheet
13. Syntax: collections List ("one" 2 3 3) Vector ["one" 2 3 3] Set #{"one" 2 3} Map {:name "Pablo", :age 28} (:age {:name "Pablo", :age 28})  28
14. Syntax: functions Call (+ 1 2 3) Definition (defn abs [n] (if (neg? n) (- n) n)) Anonymous definition (fn [x y] (+ (abs x) (abs y))) Sugared anonymous definition #(+ (abs %1) (abs %2)) condition then else vector list fn args
15. Vocabulary: functions (def coll [-42 5 -0.1]) (map abs coll)  (42 5 0.1) (reduce + 0 coll)  -37.1 (filter neg? coll)  (-42 -0.1)
16. Interop Java Clojure new JFrame("Titre") (JFrame. "Titre") Color.RED Color/RED frame.setTitle("Titre2") (.setTitle frame "Titre2") frame.getTitle().toLowerCase() (.. frame getTitle toLowerCase) frame.add(panel) frame.pack() frame.setVisible(true) (doto frame (.add panel) (.pack) (.setVisible true)) 2 4 1 3
17. Practical part
18. What to install? • Nothing! <dependency> <groupId>org.clojure</groupId> <artifactId>clojure</artifactId> <version>1.4.0</version> </dependency> • What’s in the JAR? – The library – REPL: java -jar clojure.jar – Compiler: .clj  .class
19. Tools • Build – leiningen – clojure-maven-plugin • IDE – Counterclockwise (Eclipse) – La Clojure (IntelliJ IDEA) – Emacs!
20. Resources • Presentations: – blip.tv/clojure – infoq.com/clojure • Books: – clojurebook.com – joyofclojure.com • Exercises: – 4clojure.com
21. Questions?
22. Image credits • Clojure logo: © Tom Hickey (tomhickey.com) • Aerial view of the LHC: © 2001 CERN (cdsweb.cern.ch/record/42370) • The Treachery of Images: © 1929 René Magritte • Duke models: © Sun Microsystems Inc. (duke.kenai.com/models) • Portrait of John McCarthy: © 2006 null0 (flic.kr/p/q39Sg) • The Call of the Peaks: © 1942 René Magritte • Clairvoyance: © 1936 René Magritte • Cooled Beans: © 2008 Chris Bay (flic.kr/p/4z6CBA) • Gears: © Dima Yagnyuk (thenounproject.com/noun/gears/#icon- No2174, thenounproject.com/Deadtype) • Tools: © Jacob Hardbower (thenounproject.com/noun/tools/#icon- No4684, thenounproject.com/HeartWired)