My Clojure talk at GNUnify 2010.

1. Functional Programming on the JVM
using Clojure
Baishampayan Ghose
Infinitely Beta Technologies
GNUnify 2010
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2. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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3. Who am I?
My name is BG and I am a Computer guy
FP head
Scale nerd
Prog-lang lawyer
Web standards ninja
FOSS geek
Startup-ist
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4. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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5. What, why and how of Clojure
What is Clojure?
Why a new programming language?
How is Clojure any better than X?
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6. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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7. Fundamentals
Clojure is a Lisp
Clojure is dynamic
Clojure is hosted on the JVM
Clojure is functional
Clojure is geared towards concurrency
Free & Open Source
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8. Integers — 1234567891234
Doubles — 3.14, BigDecimals — 1.23M
Ratios — 22/4
Strings — “foo”, Characters — a b c
Symbols — foo bar, Keyword — :foo :bar
Booleans — true false, Null — nil
Regex patterns — #“[a-zA-Z0-9]”
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9. Data Structures
Lists
(1 2 3 4 5), (foo bar baz), (list 1 2 3)
Vectors
[1 2 3 4 5], [foo bar baz], (vector 1 2 3)
Maps
{:a 1 :b 2 :c 3}, (hash-map :x 1 :y 2)
Sets
#{foo bar baz}
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10. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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11. Syntax
There is no other syntax!
Data structures are the code
No other text based syntax, just different
interpretations
There is a fancy name for this — Homoiconicity
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12. Syntax
There is no other syntax!
Data structures are the code
No other text based syntax, just different
interpretations
There is a fancy name for this — Homoiconicity
Everything is an expression
All data literals stand for themselves, except —
Symbols
Lists
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13. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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14. Hello, Clojure!
hello.clj
(ns hello)
(defn hello
"Say hello to name"
[name]
(str "Hello, " name "!"))
(hello "Clojure") ; -> "Hello, Clojure!"
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15. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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16. Sequences
An abstraction over traditional Lisp lists
Provides an uniform way of walking through data
structures
(seq coll)
If collection is non-empty, return a sequence object
(first s)
Return the first item
(rest s)
Return a seq of the rest of elements
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17. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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18. Java Inter-op
Wrapper free interface to Java
Syntactic sugar to make Java invocation easy
Core Clojure abstractions are Java interfaces
Clojure functions implement Callable & Runnable
Clojure sequence library works on Java iterables
Easy to implement, extend Java interfaces (if
needed)
Almost identical to Java in terms of speed
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19. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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20. Concurrency
Simultaneous execution
Avoid reading,yielding inconsistent data
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21. Concurrency
Simultaneous execution
Avoid reading,yielding inconsistent data
Synchronous Asynchronous
Coordinated ref
Independent atom agent
Unshared var
Table: Building blocks of Clojure concurrency
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22. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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23. Multimethods
Generalised indirect dispatch
Dispatch on a arbitrary function of the arguments
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24. Multimethods
Generalised indirect dispatch
Dispatch on a arbitrary function of the arguments
Call sequence
Call dispatch function on args to get dispatch value
Find method associated with dispatch value
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25. Multimethods
Generalised indirect dispatch
Dispatch on a arbitrary function of the arguments
Call sequence
Call dispatch function on args to get dispatch value
Find method associated with dispatch value
Else call default method, else error
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26. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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27. There is more!
Metadata
Destructuring
Transients
Zippers
Futures, Promises
clojure.contrib
Ping me after the talk for details
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28. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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29. Tools
Emacs + SLIME + paredit
ViMClojure
Enclojure + IntelliJ IDEA
Counterclockwise + Eclipse
Leiningen
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30. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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31. Resources
Programming Clojure by Stuart Halloway
http://en.wikibooks.org/wiki/Clojure
http://clojure.org
http://groups.google.com/group/clojure
http://planet.clojure.in
http://clojure.blip.tv
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32. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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33. Questions?
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34. Outline
1 Who am I?
2 What, why and how of Clojure
3 Fundamentals
4 Syntax
5 Hello, Clojure!
6 Sequences
7 Java Inter-op
8 Concurrency
9 Multimethods
10 There is more!
11 Tools
12 Resources
13 Q&A
14 Contacting me
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35. Contacting me
http://freegeek.in/
bg@infinitelybeta.com
@ghoseb on Twitter
Slides on - http://bit.ly/gnunify-clojure
Infinitely Beta is recruiting smart hackers!
http://infinitelybeta.com/jobs/
CC BY SA
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