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Clojure Lauro Caetano 14/01/2014

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Just an introduction

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• Intro (Syntax, Data Structures, Functions) • Persistent Data Structures • Macros • Famous projects • Should I use Clojure? • Learn more.

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• Clojure is a dynamic programming language that targets the Java Virtual Machine. • Clojure is a dialect of Lisp (code as data). • Functional (features a rich set of immutable, persistent data structure). • When mutable state is needed, Clojure offers a software transactional memory system and reactive Agent system that ensure clean, correct, multithreaded designs.

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• All operations have this form: (operator operands)

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• Other languages mixes infix notation, dot operators and parentheses. Example:

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• Nil, String, numbers, keywords, symbols, collections…

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• Collections are immutable and persistent.

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• Maps are similar to dictionaries or hashes in other languages. They are a way of associating some value with some other value.

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• Vector is similar to an Array.

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• Lists are similar to vector in that they are linear collections of values.

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• Sets are collections of unique values.

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• Functions

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• Clojure evaluates all function arguments recursively before passing them to the function.

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• Valid function calls

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• Persistent Data Structures.

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• There is no Clojure equivalent for the following Ruby:

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• Ok.. Immutable, but what about persistent?

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• While persistence can be achieved by simple copying, this is inefficient in CPU and RAM usage, because most operations make only small changes to a data structure.

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• A better method is to exploit the similarity between the new and old versions to share structure between them, such as using the same subtree in a number of tree structures. • (Fat Node, Path Copying, A combination)

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• Macros

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• Macro is a tool for transforming an arbitrary data structure into one which can be evaluated by Clojure. (Allows new syntax)

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• the -> (threading macro)

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• Famous Projects

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• Should I use Clojure?

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• Learn. • Improve the way you write code in other languages. • Motivation.

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• Learn more

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• References • https://github.com/clojure/clojure • clojure.org • http://en.wikipedia.org/wiki/ Persistent_data_structure • http://www.braveclojure.com/ • http://www.infoq.com/presentations/Value- Identity-State-Rich-Hickey