Into Clojure

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

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

Literaler
"String" ;=> String

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

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

Collection literaler
; List
'(3 2 1)

; Vector
[1 2 3]

; Set
#{1 2 3}

; Map
{1 "one", 2 "two"‚ 3 "three"}

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")

Dette er en liste

'(+ 1 2)
;=> (+ 1 2)

Dette er en form

(+ 1 2)
;=> 3

Preﬁks notasjon

(+ 1 2)
;=> 3

Dette er en form

(apply + '(1 2))
;=> 3

Dette er en java.lang.String

"(+ 1 2)"
;=> "(+ 1 2)"

som kan konverteres til en form

(read-string "(+ 1 2)")
;=> (+ 1 2)

som kan konverteres til en form
som kan evalueres

(eval (read-string "(+ 1 2)"))
;=> 3

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

Funksjoner

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

Funksjoner

((fn [n] (* 2 n)) 4)

Funksjoner

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

Funksjoner

(fn [n] (* 2 n))
#(* 2 %)

Funksjoner

(fn [n] (* 2 n))
#(* 2 %)
#(* 2 %1)

Funksjoner & Vars

(def times-two
(fn [n] (* 2 n)))
;=> #'user/times-two

Funksjoner & Vars

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

Funksjoner & Vars

(def times-two
(fn [n] (* 2 n)))

(defn times-two
[n] (* 2 n))

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

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)

Immutable collections
; List
'(3 2 1)

; Vector
[1 2 3]

; Set
#{1 2 3}

; Map
{1 "one", 2 "two"‚ 3 "three"}

ﬁrst
(first '(1 2 3))

(first [1 2 3])

(first #{1 2 3})

(first {:one "one" :two "two"})

ﬁrst
(first '(1 2 3))
;=> 1

(first [1 2 3])
;=> 1

(first #{1 2 3})
;=> 1


ﬁrst
(first '(1 2 3))
;=> 1

(first [1 2 3])
;=> 1

(first #{1 2 3})
;=> 1

;=> [:one "one"]

rest
(rest '(1 2 3))

(rest [1 2 3])

(rest #{1 2 3})

(rest {:one "one" :two "two"})

rest
(rest '(1 2 3))
;=> (2 3)

(rest [1 2 3])
;=> (2 3)

(rest #{1 2 3})
;=> (2 3)


rest
(rest '(1 2 3))
;=> (2 3)

(rest [1 2 3])
;=> (2 3)

(rest #{1 2 3})
;=> (2 3)

;=> ([:two "two"])

rest
(rest '())

(rest [])

(rest #{})

(rest {})

rest
(rest '())
;=> ()

(rest [])
;=> ()

(rest #{})
;=> ()

(rest {})
;=> ()

get
(get '(1 2 3) 0)

(get [1 2 3] 0)

(get #{3 2 1} 1)

(get {:one 1 :two 2 :three 3} :one)

get
(get '(1 2 3) 0)

(get [1 2 3] 0)
;=> 1

(get #{3 2 1} 1)


get
(get '(1 2 3) 0)

(get [1 2 3] 0)
;=> 1

(get #{3 2 1} 1)
;=> 1


get
(get '(1 2 3) 0)

(get [1 2 3] 0)
;=> 1

(get #{3 2 1} 1)
;=> 1

;=> 1

get
(get '(1 2 3) 0)
;=> nil

(get [1 2 3] 0)
;=> 1

(get #{3 2 1} 1)
;=> 1

;=> 1

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

collections er
('(1 2 3) 0)
funksjoner

([1 2 3] 0)

(#{3 2 1} 1)

({:one 1 :two 2 :three 3} :one)

collections er
('(1 2 3) 0)
funksjoner

([1 2 3] 0)
;=> 1

(#{3 2 1} 1)
;=> 1

;=> 1

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

;=> 1

contains?
(contains? '(10 11 12) 10)

(contains? '[10 11 12] 1)

(contains? #{3 2 1} 1)

(contains? {:one 1 :two 2 :three 3} :one)

contains?
(contains? '(10 11 12) 10)

(contains? '[10 11 12] 1)

(contains? #{3 2 1} 1)
;=> true


contains?
(contains? '(10 11 12) 10)

(contains? '[10 11 12] 1)

(contains? #{3 2 1} 1)
;=> true

;=> true

contains?
(contains? '(10 11 12) 10)
;=> false

(contains? '[10 11 12] 1)

(contains? #{3 2 1} 1)
;=> true

;=> true

contains?
(contains? '(10 11 12) 10)
;=> false

(contains? '[10 11 12] 1)
;=> true

(contains? #{3 2 1} 1)
;=> true

;=> true

.contains
(.contains '(10 11 12) 10)

(.contains '[10 11 12] 1)

(.contains #{3 2 1} 1)

(.contains {:one 1 :two 2 :three 3} :one)

.contains
(.contains '(10 11 12) 10)
;=> true

(.contains '[10 11 12] 1)
;=> false

(.contains #{3 2 1} 1)
;=> true


.contains
(.contains '(10 11 12) 10)
;=> true

(.contains '[10 11 12] 1)
;=> false

(.contains #{3 2 1} 1)
;=> true

;=> java.lang.IllegalArgumentException: No matching method
found: contains for class clojure.lang.PersistentArrayMap

.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

Java interop

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

Java interop

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

(java.util.ArrayList.)
;=> #<ArrayList []>

Java interop
(System/currentTimeMillis)
;=> 1318164613423

(.size (new java.util.ArrayList))
;=> 0

(. (new java.util.ArrayList) size)
;=> 0

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

(defmacro infix [form]
(list (second form) (first form) (first (nnext form))))
;=> #'user/infix

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

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

;=> #'user/infix

(macroexpand '(infix (1 + 2)))
;=> (+ 1 2)

Makroer

;=> #'user/infix

`(~(second form) ~(first form) ~@(nnext form)))
;=> #'user/infix

Makroer
• The two rules of the macro club

Programming Clojure - Stuart Halloway 2009

Makroer
1. Don’t write macros.


Makroer
2. Only write macros if that is the only way to
encapsulate a pattern.


Makroer
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.


REPL demo
“late collections/funksjoner”

Into Clojure

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Editor's Notes