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 2

It looks like this... (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)) 3

Primitives 4

Collections 5

Sequences 6

Functions 7

Compiler 8

Casting spells 9

Creating functions 10

An example... 11

map 12

Sequence of lines 13

Sequence of files 14

Sequence functions 15

You 16

Lazy sequences 17

Power 19

Objects 20

Maps as cheap objects 21

Records 22

Javapackage domain; int result = 1; result = prime * result + Float.floatToIntBits(alcohol);public class Beer { result = prime * result + ((beer == null) ? 0 : beer.hashCode()); private String beer; result = prime * result + ((brewery == null) ? 0 : private String brewery; brewery.hashCode()); private float alcohol; result = prime * result + ibu; private int ibu; return result; } public Beer(String beer, String brewery, float alcohol, int ibu) { super(); @Override this.beer = beer; public boolean equals(Object obj) { this.brewery = brewery; if (this == obj) this.alcohol = alcohol; return true; this.ibu = ibu; if (obj == null) } return false; if (getClass() != obj.getClass()) public String getBeer() { return false; return beer; Beer other = (Beer) obj; } if (Float.floatToIntBits(alcohol) != Float public String getBrewery() { .floatToIntBits(other.alcohol)) return brewery; return false; } if (beer == null) { public float getAlcohol() { if (other.beer != null) return alcohol; return false; } } else if (!beer.equals(other.beer)) public int getIbu() { return false; return ibu; if (brewery == null) { } if (other.brewery != null) public void setBeer(String beer) { return false; this.beer = beer; } else if (!brewery.equals(other.brewery)) } return false; public void setBrewery(String brewery) { if (ibu != other.ibu) this.brewery = brewery; return false; } return true; public void setAlcohol(float alcohol) { } this.alcohol = alcohol; } @Override public void setIbu(int ibu) { public String toString() { this.ibu = ibu; return "Beer [beer=" + beer + ", brewery=" + brewery + ", } alcohol=" + alcohol + ", ibu=" + ibu + "]"; } @Override } public int hashCode() { final int prime = 31; 23

Javapackage domain; int result = 1; result = prime * result + Float.floatToIntBits(alcohol);public class Beer { result = prime * result + ((beer == null) ? 0 : beer.hashCode()); private String beer; result = prime * result + ((brewery == null) ? 0 : private String brewery; brewery.hashCode()); private float alcohol; Fields and types result = prime * result + ibu; private int ibu; } return result; Hashing public Beer(String beer, String brewery, float alcohol, int ibu) { super(); @Override this.beer = beer; public boolean equals(Object obj) { this.brewery = brewery; this.alcohol = alcohol; Construction if (this == obj) return true; Equality this.ibu = ibu; if (obj == null) } return false; if (getClass() != obj.getClass()) public String getBeer() { return false; return beer; Beer other = (Beer) obj; } if (Float.floatToIntBits(alcohol) != Float public String getBrewery() { .floatToIntBits(other.alcohol)) return brewery; return false; } public float getAlcohol() { Getters if (beer == null) { if (other.beer != null) return alcohol; return false; } } else if (!beer.equals(other.beer)) public int getIbu() { return false; return ibu; if (brewery == null) { } if (other.brewery != null) public void setBeer(String beer) { return false; this.beer = beer; } else if (!brewery.equals(other.brewery)) } return false; public void setBrewery(String brewery) { if (ibu != other.ibu) this.brewery = brewery; return false; } return true; public void setAlcohol(float alcohol) { this.alcohol = alcohol; Setters } } @Override public void setIbu(int ibu) { public String toString() { this.ibu = ibu; return "Beer [beer=" + beer + ", brewery=" + brewery + ", } alcohol=" + alcohol + ", ibu=" + ibu + "]"; Printing } @Override } public int hashCode() { final int prime = 31; 23

Data interfaces 24

Data interfaces 25

Data - Clojure vs Java 26

Polymorphism 27

Generic access FTW 28

Multimethods 29

Multimethod dispatch 30

Protocols 31

State 32

Atoms 33

Refs 34

Agents 35

Destructuring 36

for comprehensions 37

Macros 38

Macros 39

Review CONCURRENCY HOST DATA CODE 40

Review CONCURRENCY HOST DATA CODE primitives 40

Review CONCURRENCY HOST DATA CODE collections primitives 40

Review CONCURRENCY HOST sequences DATA CODE collections primitives 40

Review CONCURRENCY HOST laziness sequences DATA CODE collections primitives 40

Review CONCURRENCY HOST laziness sequences FP DATA CODE collections primitives 40

Review CONCURRENCY HOST laziness sequence library sequences FP DATA CODE collections primitives 40

Review CONCURRENCY HOST laziness sequence library sequences FP records types DATA CODE collections primitives 40

Review CONCURRENCY HOST laziness sequence library sequences multimethods FP protocols records types DATA CODE collections primitives 40

Review refs agentsatoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA CODE collections primitives 40

Review refs agentsatoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA CODE collections primitives destructuring 40

Review refs agentsatoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA macros CODE collections primitives destructuring 40

Review refs agentsatoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA macros CODE metadata collections primitives destructuring transients 40

Review refs agentsatoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA macros CODE metadata collections namespaces primitives destructuring transients 40

Review refs agentsatoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types recursion DATA macros CODE metadata collections namespaces primitives destructuring transients 40

Review refs agentsatoms CONCURRENCY HOST state Java libs laziness sequence library Java sequences interop multimethods FP protocols records types recursion DATA macros CODE metadata collections namespaces primitives destructuring transients 40

Review futures promises refs agentsatoms pmap CONCURRENCY HOST state Java libs laziness sequence library Java sequences interop multimethods FP protocols records types recursion DATA macros CODE metadata collections namespaces primitives destructuring transients 40

Conways Life Lifes rules: If alive and 2 or 3 neighbors Then stay alive Else die If dead and 3 neighbors Then come to life "Blinker" conﬁguration Implementation courtesy of Christophe Grand http://clj-me.cgrand.net/2011/08/19/conways-game-of-life/ 41

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! 43

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Cracking clojure

by Alex Miller on Nov 16, 2011

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