The document outlines an agenda for a Clojure meetup, including introductions to Clojure, incremental development with Clojure, Emacs and SLIME, Clojure STM, and a talk on optimization titled "Eratosthenes' Sieve: An Adventure in Optimization". It then provides examples of Clojure literals, collections, functions, macros, and interoperability with Java.

1. 11.10.2011

2. Agenda
• Intro til Clojure
- Alf Kristian Støyle
• Inkrementell utvikling med Clojure, Emacs og SLIME
- Stig Henriksen
• Clojure STM
- Ole Christian Rynning
• Eratosthenes' sil: et eventyr om optimalisering
- Bodil Stokke

3. Clojure
• General purpose
• Lisp (List Processing)
• Funksjonelt
• Kompilert
• Dynamisk typet

4. Literaler
"String" ;=> String

5. Literaler
"String"
(class "String") ;=> java.lang.String
String

6. Literaler
(class "String"
"String") ;=> String
java.lang.String
(class #"regex") ;=> java.util.regex.Pattern
(class 123) ;=> java.lang.Integer
(class 2147483648) ;=> java.lang.Long
(class 123M) ;=> java.math.BigDecimal
(class 123N) ;=> clojure.lang.BigInt
(class true) ;=> java.lang.Boolean
(class false) ;=> java.lang.Boolean
(class 42/43) ;=> clojure.lang.Ratio
(class c) ;=> java.lang.Character
(class 'foo) ;=> clojure.lang.Symbol
(class :bar) ;=> clojure.lang.Keyword
(class nil) ;=> nil

7. Collection literaler
; List
'(3 2 1)
; Vector
[1 2 3]
; Set
#{1 2 3}
; Map
{1 "one", 2 "two"‚ 3 "three"}

8. Collection literaler
; List
'(3 2 1) -> (list 3 2 1)
; Vector
[1 2 3] -> (vector 1 2 3)
; Set
#{1 2 3} -> (hash-set 1 2 3)
; Map
{1 "one", 2 "two"‚ 3 "three"} ->
(hash-map 1 "one", 2 "two", 3 "three")

9. Dette er en liste
'(+ 1 2)

10. Dette er en liste
'(+ 1 2)
;=> (+ 1 2)

11. Dette er en form
(+ 1 2)

12. Dette er en form
(+ 1 2)
;=> 3

13. Dette er en form
(+ 1 2)
;=> 3

14. Dette er en form
(+ 1 2)
;=> 3

15. Dette er en form
(+ 1 2)
;=> 3

16. Prefiks notasjon
(+ 1 2)
;=> 3

17. Dette er en form
(apply + '(1 2))
;=> 3

18. Dette er en form
(apply + '(1 2))
;=> 3

19. Dette er en form
(apply + '(1 2))
;=> 3

20. Dette er en java.lang.String
"(+ 1 2)"
;=> "(+ 1 2)"

21. Dette er en java.lang.String
som kan konverteres til en form
(read-string "(+ 1 2)")
;=> (+ 1 2)

22. Dette er en java.lang.String
som kan konverteres til en form
som kan evalueres
(eval (read-string "(+ 1 2)"))
;=> 3

23. Read-compile-evaluate
1. Tekst konverteres til forms
2. Forms blir konvertert til bytekode av
compiler
3. Bytekode evalueres

24. Funksjoner
(fn [n] (* 2 n))

25. Funksjoner
(fn [n] (* 2 n))
;=> #<core$eval376$fn__377 user$eval376$fn__377@5c76458f>

26. Funksjoner
((fn [n] (* 2 n)) 4)

27. Funksjoner
((fn [n] (* 2 n)) 4)
;=> 8

28. Funksjoner
(fn [n] (* 2 n))
#(* 2 %)

29. Funksjoner
(fn [n] (* 2 n))
#(* 2 %)
#(* 2 %1)

30. Funksjoner & Vars
(def times-two
(fn [n] (* 2 n)))
;=> #'user/times-two

31. Funksjoner & Vars
(def times-two
(fn [n] (* 2 n)))
;=> #'user/times-two
(times-two 4)
;=> 8

32. Funksjoner & Vars
(def times-two
(fn [n] (* 2 n)))
(defn times-two
[n] (* 2 n))

33. Immutable og persistente
datastrukturer
(def my-list '(3 2 1))
; => (3 2 1)

34. Immutable og persistente
datastrukturer
(def my-list '(3 2 1))
; => (3 2 1)

35. Immutable og persistente
datastrukturer
(def my-list '(3 2 1))
; => (3 2 1)
(def my-other-list (cons 4 my-list))
; => (4 3 2 1)

36. Immutable og persistente
datastrukturer
(def my-list '(3 2 1))
; => (3 2 1)
(def my-other-list (cons 4 my-list))
; => (4 3 2 1)

37. Immutable collections
; List
'(3 2 1)
; Vector
[1 2 3]
; Set
#{1 2 3}
; Map
{1 "one", 2 "two"‚ 3 "three"}

38. first
(first '(1 2 3))
(first [1 2 3])
(first #{1 2 3})
(first {:one "one" :two "two"})

39. first
(first '(1 2 3))
;=> 1
(first [1 2 3])
;=> 1
(first #{1 2 3})
;=> 1
(first {:one "one" :two "two"})

40. first
(first '(1 2 3))
;=> 1
(first [1 2 3])
;=> 1
(first #{1 2 3})
;=> 1
(first {:one "one" :two "two"})
;=> [:one "one"]

41. rest
(rest '(1 2 3))
(rest [1 2 3])
(rest #{1 2 3})
(rest {:one "one" :two "two"})

42. rest
(rest '(1 2 3))
;=> (2 3)
(rest [1 2 3])
;=> (2 3)
(rest #{1 2 3})
;=> (2 3)
(rest {:one "one" :two "two"})

43. rest
(rest '(1 2 3))
;=> (2 3)
(rest [1 2 3])
;=> (2 3)
(rest #{1 2 3})
;=> (2 3)
(rest {:one "one" :two "two"})
;=> ([:two "two"])

44. rest
(rest '())
(rest [])
(rest #{})
(rest {})

45. rest
(rest '())
;=> ()
(rest [])
;=> ()
(rest #{})
;=> ()
(rest {})
;=> ()

46. get
(get '(1 2 3) 0)
(get [1 2 3] 0)
(get #{3 2 1} 1)
(get {:one 1 :two 2 :three 3} :one)

47. get
(get '(1 2 3) 0)
(get [1 2 3] 0)
;=> 1
(get #{3 2 1} 1)
(get {:one 1 :two 2 :three 3} :one)

48. get
(get '(1 2 3) 0)
(get [1 2 3] 0)
;=> 1
(get #{3 2 1} 1)
;=> 1
(get {:one 1 :two 2 :three 3} :one)

49. get
(get '(1 2 3) 0)
(get [1 2 3] 0)
;=> 1
(get #{3 2 1} 1)
;=> 1
(get {:one 1 :two 2 :three 3} :one)
;=> 1

50. get
(get '(1 2 3) 0)
;=> nil
(get [1 2 3] 0)
;=> 1
(get #{3 2 1} 1)
;=> 1
(get {:one 1 :two 2 :three 3} :one)
;=> 1

51. get
(get '(1 2 3) 0 "yay")
;=> yay
(get [1 2 3] -1 "yay")
;=> yay
(get #{3 2 1} 0 "yay")
;=> yay
(get {:one 1 :two 2 :three 3} :zero "yay")
;=> yay

52. collections er
('(1 2 3) 0)
funksjoner
([1 2 3] 0)
(#{3 2 1} 1)
({:one 1 :two 2 :three 3} :one)

53. collections er
('(1 2 3) 0)
funksjoner
([1 2 3] 0)
;=> 1
(#{3 2 1} 1)
;=> 1
({:one 1 :two 2 :three 3} :one)
;=> 1

54. noen collections er
funksjoner
('(1 2 3) 0)
;=> java.lang.ClassCastException: clojure.lang.PersistentList cannot be cast to clojure.lang.IFn
([1 2 3] 0)
;=> 1
(#{3 2 1} 1)
;=> 1
({:one 1 :two 2 :three 3} :one)
;=> 1

55. contains?
(contains? '(10 11 12) 10)
(contains? '[10 11 12] 1)
(contains? #{3 2 1} 1)
(contains? {:one 1 :two 2 :three 3} :one)

56. contains?
(contains? '(10 11 12) 10)
(contains? '[10 11 12] 1)
(contains? #{3 2 1} 1)
;=> true
(contains? {:one 1 :two 2 :three 3} :one)

57. contains?
(contains? '(10 11 12) 10)
(contains? '[10 11 12] 1)
(contains? #{3 2 1} 1)
;=> true
(contains? {:one 1 :two 2 :three 3} :one)
;=> true

58. contains?
(contains? '(10 11 12) 10)
;=> false
(contains? '[10 11 12] 1)
(contains? #{3 2 1} 1)
;=> true
(contains? {:one 1 :two 2 :three 3} :one)
;=> true

59. contains?
(contains? '(10 11 12) 10)
;=> false
(contains? '[10 11 12] 1)
;=> true
(contains? #{3 2 1} 1)
;=> true
(contains? {:one 1 :two 2 :three 3} :one)
;=> true

60. .contains
(.contains '(10 11 12) 10)
(.contains '[10 11 12] 1)
(.contains #{3 2 1} 1)
(.contains {:one 1 :two 2 :three 3} :one)

61. .contains
(.contains '(10 11 12) 10)
;=> true
(.contains '[10 11 12] 1)
;=> false
(.contains #{3 2 1} 1)
;=> true
(.contains {:one 1 :two 2 :three 3} :one)

62. .contains
(.contains '(10 11 12) 10)
;=> true
(.contains '[10 11 12] 1)
;=> false
(.contains #{3 2 1} 1)
;=> true
(.contains {:one 1 :two 2 :three 3} :one)
;=> java.lang.IllegalArgumentException: No matching method
found: contains for class clojure.lang.PersistentArrayMap

63. .contains
(.contains '(10 11 12) 10)
;=> true
(.contains '[10 11 12] 1)
;=> false
(.contains #{3 2 1} 1)
;=> true
(.containsKey {:one 1 :two 2 :three 3} :one)
;=> true

64. Java interop
(new java.util.ArrayList)
;=> #<ArrayList []>

65. Java interop
(new java.util.ArrayList)
;=> #<ArrayList []>
(java.util.ArrayList.)
;=> #<ArrayList []>

66. Java interop
(System/currentTimeMillis)
;=> 1318164613423
(.size (new java.util.ArrayList))
;=> 0
(. (new java.util.ArrayList) size)
;=> 0

67. Makroer
(infix (1 + 2))
;=> 3

68. Makroer
(infix (1 + 2))
;=> 3
(defmacro infix [form]
(list (second form) (first form) (first (nnext form))))
;=> #'user/infix

69. Read-compile-evaluate
1. Tekst konverteres til forms
2. Forms blir konvertert til bytekode av
compiler
3. Dersom compiler finner en makro,
ekspander makro og begynn på 1.
4. Bytekode evalueres

70. Makroer
(infix (1 + 2))
;=> 3
(defmacro infix [form]
(list (second form) (first form) (first (nnext form))))
;=> #'user/infix

71. Makroer
(infix (1 + 2))
;=> 3
(defmacro infix [form]
(list (second form) (first form) (first (nnext form))))
;=> #'user/infix
(macroexpand '(infix (1 + 2)))
;=> (+ 1 2)

72. Makroer
(defmacro infix [form]
(list (second form) (first form) (first (nnext form))))
;=> #'user/infix
(defmacro infix [form]
`(~(second form) ~(first form) ~@(nnext form)))
;=> #'user/infix

73. Makroer
• The two rules of the macro club
Programming Clojure - Stuart Halloway 2009

74. Makroer
• The two rules of the macro club
1. Don’t write macros.
Programming Clojure - Stuart Halloway 2009

75. Makroer
• The two rules of the macro club
1. Don’t write macros.
2. Only write macros if that is the only way to
encapsulate a pattern.
Programming Clojure - Stuart Halloway 2009

76. Makroer
• The two rules of the macro club
1. Don’t write macros.
2. Only write macros if that is the only way to
encapsulate a pattern.
3. You can write any macro that makes life
easier for your callers when compared
with an equivalent function.
Programming Clojure - Stuart Halloway 2009

77. REPL demo
“late collections/funksjoner”