This document is a presentation on functional programming using Clojure on the JVM. The presentation covers an introduction to Clojure including what it is, why it was created, and how it is better than other languages. It then discusses Clojure fundamentals like being a Lisp, being dynamic and functional. The remainder of the presentation covers Clojure syntax, basics like Hello World, sequences, Java interoperability, concurrency, multimethods, tools and resources for Clojure.

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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