Cracking ClojureAlex MillerRevelytix

Clojure• A Lisp on the JVM (also ClojureScript on JavaScript)

• Dynamic (types, code, etc)• Functional language• Compiled (there is no interpreter)• Immutability and state management• Code is data • REPL - Read / Eval / Print / Loop• Interactive development

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It looks like this...

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(defn neighbors [[x y]] (for [dx [-1 0 1] dy (if (zero? dx) [-1 1] [-1 0 1])] [(+ dx x) (+ dy y)]))

(defn live [n alive?] (or (= n 3) (and (= n 2) alive?)))

(defn step [world] (set (for [[cell n] (frequencies (mapcat neighbors world)) :when (live n (world cell))] cell)))

(defn life [initial-world] (iterate step initial-world))

Primitives

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Collections

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Sequences

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Sequences

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Functions

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Functions

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Functions

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Compiler

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Casting spells

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Creating functions

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Creating functions

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Creating functions

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Creating functions

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Creating functions

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An example...

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map

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Sequence of lines

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Sequence of files

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Sequence of files

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Sequence functions

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You

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Lazy sequences

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18

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Power

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Objects

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Maps as cheap objects

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Records

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Java

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package domain;

public class Beer { private String beer; private String brewery; private float alcohol; private int ibu; public Beer(String beer, String brewery, float alcohol, int ibu) { super(); this.beer = beer; this.brewery = brewery; this.alcohol = alcohol; this.ibu = ibu; }

public String getBeer() { return beer; } public String getBrewery() { return brewery; } public float getAlcohol() { return alcohol; } public int getIbu() { return ibu; } public void setBeer(String beer) { this.beer = beer; } public void setBrewery(String brewery) { this.brewery = brewery; } public void setAlcohol(float alcohol) { this.alcohol = alcohol; } public void setIbu(int ibu) { this.ibu = ibu; }

@Override public int hashCode() { final int prime = 31;

int result = 1; result = prime * result + Float.floatToIntBits(alcohol); result = prime * result + ((beer == null) ? 0 : beer.hashCode()); result = prime * result + ((brewery == null) ? 0 : brewery.hashCode()); result = prime * result + ibu; return result; }

@Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Beer other = (Beer) obj; if (Float.floatToIntBits(alcohol) != Float .floatToIntBits(other.alcohol)) return false; if (beer == null) { if (other.beer != null) return false; } else if (!beer.equals(other.beer)) return false; if (brewery == null) { if (other.brewery != null) return false; } else if (!brewery.equals(other.brewery)) return false; if (ibu != other.ibu) return false; return true; }

@Override public String toString() { return "Beer [beer=" + beer + ", brewery=" + brewery + ", alcohol=" + alcohol + ", ibu=" + ibu + "]"; }}

Java

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package domain;

public class Beer { private String beer; private String brewery; private float alcohol; private int ibu; public Beer(String beer, String brewery, float alcohol, int ibu) { super(); this.beer = beer; this.brewery = brewery; this.alcohol = alcohol; this.ibu = ibu; }

public String getBeer() { return beer; } public String getBrewery() { return brewery; } public float getAlcohol() { return alcohol; } public int getIbu() { return ibu; } public void setBeer(String beer) { this.beer = beer; } public void setBrewery(String brewery) { this.brewery = brewery; } public void setAlcohol(float alcohol) { this.alcohol = alcohol; } public void setIbu(int ibu) { this.ibu = ibu; }

@Override public int hashCode() { final int prime = 31;

int result = 1; result = prime * result + Float.floatToIntBits(alcohol); result = prime * result + ((beer == null) ? 0 : beer.hashCode()); result = prime * result + ((brewery == null) ? 0 : brewery.hashCode()); result = prime * result + ibu; return result; }

@Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Beer other = (Beer) obj; if (Float.floatToIntBits(alcohol) != Float .floatToIntBits(other.alcohol)) return false; if (beer == null) { if (other.beer != null) return false; } else if (!beer.equals(other.beer)) return false; if (brewery == null) { if (other.brewery != null) return false; } else if (!brewery.equals(other.brewery)) return false; if (ibu != other.ibu) return false; return true; }

@Override public String toString() { return "Beer [beer=" + beer + ", brewery=" + brewery + ", alcohol=" + alcohol + ", ibu=" + ibu + "]"; }}

Fields and types

Construction

Getters

Setters

Hashing

Equality

Printing

Data interfaces

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Data interfaces

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Data interfaces

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Data - Clojure vs Java

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Data - Clojure vs Java

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Polymorphism

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Generic access FTW

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Multimethods

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Multimethod dispatch

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Protocols

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State

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Atoms

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Refs

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Agents

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Destructuring

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for comprehensions

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for comprehensions

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Macros

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Macros

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Review

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DATA CODE

HOSTCONCURRENCY

Review

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DATA CODE

HOSTCONCURRENCY

primitives

Review

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DATA CODE

HOSTCONCURRENCY

primitives

collections

Review

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DATA CODE

HOSTCONCURRENCY

sequences

primitives

collections

Review

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DATA CODE

HOSTCONCURRENCY

sequences

laziness

primitives

collections

Review

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DATA CODE

HOSTCONCURRENCY

sequences

laziness

FP

primitives

collections

Review

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DATA CODE

HOSTCONCURRENCY

sequences

lazinesssequence library

FP

primitives

collections

Review

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DATA CODE

HOSTCONCURRENCY

recordstypes

sequences

lazinesssequence library

FP

primitives

collections

Review

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DATA CODE

HOSTCONCURRENCY

recordstypes

sequences

lazinesssequence library

FP

primitives

collections

multimethodsprotocols

Review

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DATA CODE

HOSTCONCURRENCY

recordstypes

atoms

state

refs agents

sequences

lazinesssequence library

FP

primitives

collections

multimethodsprotocols

Review

40

DATA CODE

HOSTCONCURRENCY

recordstypes

atoms

state

refs agents

sequences

lazinesssequence library

FP

primitives

collections

destructuring

multimethodsprotocols

Review

40

DATA CODE

HOSTCONCURRENCY

recordstypes

atoms

state

refs agents

sequences

lazinesssequence library

FP

macros

primitives

collections

destructuring

multimethodsprotocols

Review

40

DATA CODE

HOSTCONCURRENCY

metadata

recordstypes

atoms

state

refs agents

sequences

lazinesssequence library

FP

macros

primitives

collections

transientsdestructuring

multimethodsprotocols

Review

40

DATA CODE

HOSTCONCURRENCY

metadata

recordstypes

atoms

state

refs agents

sequences

lazinesssequence library

FP

macros

primitives

collections

transientsdestructuring

namespaces

multimethodsprotocols

Review

40

DATA CODE

HOSTCONCURRENCY

metadata

recordstypes

atoms

state

refs agents

sequences

lazinesssequence library

FP

macros

primitives

collections

transientsdestructuring

namespaces

recursion

multimethodsprotocols

Review

40

DATA CODE

HOSTCONCURRENCY

metadata

recordstypes

atoms

state

refs agents

sequences

lazinesssequence library

FP

macros

primitives

collections

transientsdestructuring

namespaces

recursion

multimethodsprotocols

Java interop

Java libs

Review

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DATA CODE

HOSTCONCURRENCY

metadata

recordstypes

atoms

state

refs agents

sequences

laziness

futures promises

pmap

sequence library

FP

macros

primitives

collections

transientsdestructuring

namespaces

recursion

multimethodsprotocols

Java interop

Java libs

Conway's Life

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Implementation courtesy of Christophe Grandhttp://clj-me.cgrand.net/2011/08/19/conways-game-of-life/

"Blinker" configuration

Life's rules: If alive and 2 or 3 neighbors Then stay alive Else die If dead and 3 neighbors Then come to life

Thanks!

• Twitter: @puredanger• Blog: http://tech.puredanger.com• Work: http://revelytix.com• My conferences

– Strange Loop - http://thestrangeloop.com– Clojure/West - http://clojurewest.com

If you want to pair on Clojure during Devoxx, ping me on Twitter!

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