Zero to Clojure in 90 Minutes Colin Jones Software Craftsman at 8th Light @trptcolin Thursday, August 12, 2010

What is Clojure? Thursday, August 12, 2010

(It’s a Lisp) Thursday, August 12, 2010

It runs on the JVM Thursday, August 12, 2010

Created in 2007 by Rich Hickey Thursday, August 12, 2010

Why should we care? Thursday, August 12, 2010

Learning is good. Thursday, August 12, 2010

Concurrency can be scary. Thursday, August 12, 2010

Side effects can cause a mess. Thursday, August 12, 2010

Functional programming can help Thursday, August 12, 2010

Syntax & Data Structures Thursday, August 12, 2010

Expressions (doc +) (find-doc “regex”) Thursday, August 12, 2010

Numbers Integer 42 Long 9999999999999 BigInteger 9999999999999999999 Double 4.2 BigDecimal 4000.2M Ratio 1/3 Thursday, August 12, 2010

More String “go to the” Character \p \a \r \k Regex #”\d+” Nil nil Boolean true false Keyword :really/soon Symbol some-time Thursday, August 12, 2010

Collections List (1 2 3 4 5) Vector [1 2 3 4 5] Map {:first-name “colin”, :last-name “jones”} Set #{a b c d e} Thursday, August 12, 2010

Expressions (doc +) (find-doc “regex”) Thursday, August 12, 2010

Diving in Thursday, August 12, 2010

Clojure Functional Koans http://trptcolin.github.com USB Drives Thursday, August 12, 2010

REPL => Read => Evaluate => Print Thursday, August 12, 2010

java -jar /path/to/clojure.jar (+ JRE functional-koans) => WIN! From Functional Koans directory: Mac / Linux: ./repl.sh Windows: repl From anywhere: Thursday, August 12, 2010

Functions Thursday, August 12, 2010

clojure.test user=> (is (= 1 2)) FAIL in clojure.lang.PersistentList$EmptyList@1 15) expected: (= 1 2) actual: (not (= 1 2)) false user=> (use ‘clojure.test) nil user=> (is (= 1 1)) true Thursday, August 12, 2010

Equality user=> (is (= “Colin” “Colin”)) true user=> (is (= nil nil)) true user=> (is (= ‘(1 2 3) [1 2 3])) true user=> (is (= 1.0 1 4/4)) true Thursday, August 12, 2010

Math fun(ctions) user=> (is (= 15 (+ 1 2 3 4 5))) true user=> (is (< 1 2 3)) true Thursday, August 12, 2010

Hide and seq? user=> (is (= :a (first [:a :b :c]))) true user=> (is (= [:c :b :a] (reverse [:a :b :c]))) true user=> (is (= [:b :c] (rest [:a :b :c]))) true Thursday, August 12, 2010

Defining our own functions user=> (def square-1 (fn [x] (* x x))) #‘user/square-1 user=> (defn square-3 [x] (* x x)) #‘user/square-3 user=> (def square-2 #(* % %)) #‘user/square-2 user=> (is (= 9 (square-1 3))) true user=> (is (= 9 (square-2 3))) true user=> (is (= 9 (square-3 3))) true Thursday, August 12, 2010

map user=> (defn square [x] (* x x)) #‘user/square user=> (is (= ‘(1 4 9 16 25) (map square ‘(1 2 3 4 5)))) true Thursday, August 12, 2010

filter user=> (is (= [odd?] (filter fn? [“odd” :odd odd?]))) true Thursday, August 12, 2010

apply user=> (is (= “dog” (str \d \o \g))) true user=> (is (= “dog” (str dog-letters))) FAIL in clojure.lang.PersistentList$EmptyList expected: (= “dog” (str dog-letters)) actual: (not (= “dog” “[\\d \\o \\g]”)) false user=> (def dog-letters [\d \o \g]) true user=> (is (= “dog” (apply str dog-letters))) true Thursday, August 12, 2010

Laziness Thursday, August 12, 2010

The whole numbers user=> (def whole-numbers (iterate inc 0)) #‘user/whole-numbers user=> (is (= (range 20 40) (take 20 (drop 20 whole-numbers)))) true user=> (is (= (range 0 20) (take 20 whole-numbers))) true Thursday, August 12, 2010

Let’s try it in the REPL user=> (def whole-numbers (iterate inc 0)) #‘user/whole-numbers user=> whole-numbers (0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 OH NOEZ!!! Thursday, August 12, 2010

Don’t hold onto your head user=> (def whole-numbers (iterate inc 0)) #‘user/whole-numbers user=> (first (drop 10000000 whole-numbers)) Exception in thread "main" java.lang.OutOfMemoryError: Java heap space user=> (defn whole-numbers [] (iterate inc 0)) #'user/whole-numbers user=> (first (drop 10000000 (whole-numbers))) 10000000 Thursday, August 12, 2010

BIG NUMBERS!!! Thursday, August 12, 2010

Clojure Functional Koans Thursday, August 12, 2010

Background Aaron Bedra of Relevance based on EdgeCase’s Ruby Koans Thursday, August 12, 2010

Towards Clojure Enlightement Mac / Linux: ./run.sh Windows: run Thursday, August 12, 2010

Managing State Thursday, August 12, 2010

vars user=> (def x 42) #‘user/x user=> (let [x :foo] x) :foo user=> x 42 user=> x 42 Thursday, August 12, 2010

refs user=> (def attendees (ref 30)) #‘user/attendees user=> attendees # user=> @attendees 30 user=> (alter attendees dec) java.lang.IllegalStateException: No transaction running user=> (dosync (alter attendees dec)) 29 user=> @attendees 29 Thursday, August 12, 2010

refs (defn transfer [amount a b] (dosync (alter a - amount) (alter b + amount))) (def checking (ref 10)) (def savings (ref 50)) Bank Accounts Branch (transfer 25 checking savings) snapshot (checking=10, savings=50) checking = 60, savings=0 ATM (transfer 25 checking savings) snapshot (checking=10, savings=50) commit (checking=35, savings=25) Conflict discovered! (transfer 25 checking savings) Automatic Retry: commit (checking=60, savings=0) snapshot (checking=35, savings=25) Thursday, August 12, 2010

Further Study Thursday, August 12, 2010

Books Thursday, August 12, 2010

The Internets Functional Koans http://github.com/relevance/functional-koans/tree/clojure Web docs http://clojure.org/ Google Group http://groups.google.com/group/clojure IRC #clojure on freenode.net Thursday, August 12, 2010

Questions? Thursday, August 12, 2010

Uncle Bob Martin, Corey Haines, Dave Astels, Ken Auer, Chad Fowler, Keavy McMinn, Michael Feathers, Doug Bradbury, Enrique Comba Riepenhausen, and more... Thursday, August 12, 2010