Cracking clojure
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Maybe you've heard of Clojure, one of those new-fangled JVM languages. How does anybody get any work done in a language like that? What's up with all those parentheses?If you're coming from Java and OOP, Clojure can indeed feel disorienting. In this talk we'll demystify the basics of Clojure and dissect the source of its power. Functional programming is on the rise and Clojure is indeed a functional language, but we'll learn the real secret sauce that makes cooking with Clojure fun.We'll look at how to translate concepts you know in Java (like domain objects, interfaces, collections, and concurrency) into their natural Clojure equivalents. And more importantly, we'll learn how these components interact to make Clojure a beautiful language for building abstractions.No prior knowledge of Clojure or functional programming is assumed... Clojure novices welcome!
Transcript of Cracking clojure
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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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
40
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
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DATA CODE
HOSTCONCURRENCY
recordstypes
atoms
state
refs agents
sequences
lazinesssequence library
FP
primitives
collections
destructuring
multimethodsprotocols
Review
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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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