![Data Structures Type Example Characteristics list (2 4 6 8) • singly linked • grows at front vector [2 4 6 8] • indexed • grows at end map {:fname “Rich”, :lname • key/value pairs “Hickey”} • unique key set #{2 4 6 8} • unordered • unique keys](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-31-2048.jpg)
![Function Definition define fn fn name (defn add-numbers “Add two numbers” documentation [x y] arguments (println “result: ” (+ x y))) fn body](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-36-2048.jpg)
![Essence vs Ceremony public class AddNumbers { public static void main(String args[]) { long sum = 0; for (int i = 1; i < 1001; i++) { sum += i; } System.out.println("The sum is: " + sum); } }](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-40-2048.jpg)
![Useful Functions count: returns number of items in a collection – (count *4 “hello” c+) => 3 apply: applies a function on the arguments – (apply – [10 5 2]) => 3](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-42-2048.jpg)
![REPL: Doc Documentation can be viewed with the doc macro user=> (doc +) ------------------------- clojure.core/+ ([] [x] [x y] [x y & more]) Returns the sum of nums. (+) returns 0. nil](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-44-2048.jpg)
![REPL: source Displays the source for the function user=> (source even?) (defn even? "Returns true if n is even, throws an exception if n is not an integer" {:added "1.0"} [n] (zero? (bit-and n 1))) nil](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-46-2048.jpg)
![Calling Clojure from Java public class ClojureGreeter { public static void main(String[] args) { RT.loadResourceScript("clojure_script.clj"); Var greet = RT.var("clj.sample", “say"); String result = (String) greet.invoke(“John"); System.out.println(“Greeting: " + result); } }](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-54-2048.jpg)
![Macro Example (defmacro def-print-fn [fn-name args & body] `(defn ~fn-name ~args (println "Invoking ...") ~@body)) (def-print-fn simple-call[] (println "This is a simple call function."))](https://image.slidesharecdn.com/introductiontoclojure-111011005254-phpapp02/75/Introduction-to-clojure-62-2048.jpg)
Introduction to clojure
- 1. Introduction to Clojure Programming Silicon Valley Code Camp October 8th, 2011 Abbas Raza
- 2. Myself user => (defspeaker { :name “Abbas Raza” :company “SuccessFactors” :team “Platform Engineering” :twitter “theceo”})
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- 5. Thanks! Rich Hickey ClojureCreator
- 6. What is Clojure GeneralPurpose Language Dynamic Functional Lisp Strengths Java/CLR/Javascript
- 7. Clojure - Timeline Firstreleased October 16, 2007 1.0 released 05/04/09 1.1 released 12/31/09 1.2 released 08/19/10 1.3 released 09/23/11 ClojureScript released July, 2011
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- 10. H/W Perf FreeLunch is over http://www.gotw.ca/publications/concurrency-ddj.htm
- 11. Functional Programming No sideeffects – immutable Functions are first class citizens Functions passed in as parameters Functions return functions Functions can be created at runtime
- 12. Software Transactional Memory Providestransactional feature for application in memory Implements Multi Value Concurrency Control (MVCC) Atomic, Consistent, and Isolated
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- 14. LISP Lisp is worth learning for the profound enlightenment experience you will have when you finally get it; that experience will make you a better programmer for the rest of your days, even if you never actually use Lisp itself a lot. - Eric Raymond, How to Become a Hacker
- 15. Homoiconicity Code is datais code
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- 18. Java Interop Plethora oflibraries Highly performant Wide deployment Calling Java from Clojure and vice versa
- 19. What you getfrom Clojure Power: JVM/CLR/JS Robustness: functional Concurrency: STM Focus: lisp
- 20. Suggestion Focus on thecore. Ignore the edges.
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- 22. Getting Started Download clojurezip from clojure.org/downloads Run: java –cp clojure.jar clojure.main
- 23. REPL Interactive environment forfaster development Read-Eval-Print-Loop ns expression user => (+ 3 4) 7 result user =>
- 24. Let’s code abit
- 25. Namespace Define modules Avoid collision Format: (nsname & references) Example: (ns svcc)
- 26. Symbols Symbols are usedto name functions, values, etc. Example: str or concat
- 27. Keywords A keyword islike a Symbol except that it begins with a colon (:). It resolves to itself. Example: :foo => :foo
- 28. S-expressions Stands for "symbolicexpression" List-based data structures that represent semi- structured data. Example: (def port 8080)
- 29. Form Any s-expression thatevaluates to a value Example: (+ 2 3 4)
- 30. Atomic Data Types Clojure Example Java string “hello” String character a Character integer 10 Int/Long/BigInteger double 3.14159 Double double 3.14159M BigDecimal boolean true Boolean nil nil null symbol foo, + N/A keyword :foo, ::foo N/A
- 31. Data Structures Type Example Characteristics list (2 4 6 8) • singly linked • grows at front vector [2 4 6 8] • indexed • grows at end map {:fname “Rich”, :lname • key/value pairs “Hickey”} • unique key set #{2 4 6 8} • unordered • unique keys
- 32. Sequences An abstraction overtraditional lisp lists Provides a view into the lists Are lazy Some functions on sequences: (first seq): returns first element (cons elem seq): prepends element
- 33. Syntax – (Prefix)Polish Notation The operator appears before the operands Format: (operator operand operand)
- 34. Structure list symbol string (println “Hello World”)
- 35. Semantics fncall argument (println “Hello World”)
- 36. Function Definition define fn fn name (defn add-numbers “Add two numbers” documentation [x y] arguments (println “result: ” (+ x y))) fn body
- 37. Comments Comments start witha semi-colon (do ;; line comment ;;; block comment (println “Hello World”) (println “GoodBye!”) ) ; end of line comment
- 38. Predicate It is afunction that returns a boolean. The name ends with a ?. Example: even?
- 39. Higher Order Function Functionsthat have functions are parameters. Example: map, reduce
- 40. Essence vs Ceremony publicclass AddNumbers { public static void main(String args[]) { long sum = 0; for (int i = 1; i < 1001; i++) { sum += i; } System.out.println("The sum is: " + sum); } }
- 41. Essence vs Ceremony (println(reduce + (range 1 1001)))
- 42. Useful Functions count: returnsnumber of items in a collection – (count *4 “hello” c+) => 3 apply: applies a function on the arguments – (apply – [10 5 2]) => 3
- 43. Program Flow if, if-not – (if test consequent alternative) cond, condp – (cond & clauses) when, when-not – (when test & body)
- 44. REPL: Doc Documentation canbe viewed with the doc macro user=> (doc +) ------------------------- clojure.core/+ ([] [x] [x y] [x y & more]) Returns the sum of nums. (+) returns 0. nil
- 45. REPL: javadoc Opens abrowser with the javadoc for the requested class user=> (javadoc java.util.Random) "http://java.sun.com/javase/6/docs/api/java/uti l/Random.html"
- 46. REPL: source Displays thesource for the function user=> (source even?) (defn even? "Returns true if n is even, throws an exception if n is not an integer" {:added "1.0"} [n] (zero? (bit-and n 1))) nil
- 47. REPL: inspector Creates aSwing inspector on supplied object user=> (use 'clojure.inspector) nil user=> (inspect (Math/PI))
- 49. Java Class Import Importingjava classes Format: (import & import-symbols-or-lists) Example: (import '(java.util Random) '(java.util Date))
- 50. Instantiate Java Class Format:(def instanceName (new ClassName)) Example: (def sdf (new SimpleDateFormat “yyyy-mm”)) Another way: (def sdf (SimpleDateFormat. “yyyy-mm”))
- 51. Java Member Access Format:(.method instance arguments) Example: (.parse sdf date-string)
- 52. Java Static Access Format:(Classname/staticMethod args*) Example: (Math/PI)
- 53. Calling Java fromClojure (import '(java.util Random)) (def rnd (Random.)) (.nextInt rnd 10)
- 54. Calling Clojure fromJava public class ClojureGreeter { public static void main(String[] args) { RT.loadResourceScript("clojure_script.clj"); Var greet = RT.var("clj.sample", “say"); String result = (String) greet.invoke(“John"); System.out.println(“Greeting: " + result); } }
- 55. Error Handling All exceptionsthrown are Runtime Exceptions. (try expr* catch-clause* finally-clause?) Example: (try (/ 1 0) (catch Exception e (println "in catch")) (finally (println "in finally")))
- 56. MultiMethods Provides a generalindirect dispatching mechanism Dispatches based on type values, attributes, and metadata defmulti creates new multimethods defmethod create methods for defmulti
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- 61. Macro System Allows extendingthe compiler Lot of clojure features are based on macros Transform code
- 62. Macro Example (defmacro def-print-fn[fn-name args & body] `(defn ~fn-name ~args (println "Invoking ...") ~@body)) (def-print-fn simple-call[] (println "This is a simple call function."))
- 63. Concurrency Mutation done intransaction Readers do not block writers Writers do not block readers First one to commit succeeds
- 64. Concurrency Mechanism Shared data Synchronous Coordinated Change Ref Yes Yes Yes Atom Yes Yes No Agent Yes No No Var No No No
- 65. Leinengin Build tool Commands –compile, test, jar, install, pom, repl
- 66. IDE Support Eclipse Counterclockwise IntelliJIDEA La Clojure Netbeans Enclojure JEdit Emacs Vim Clooj
- 67. Clojure and theWeb Compojure Ring Noir Heroku support
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- 70. … and onelast thing
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