Cracking clojure
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This document provides an overview of the Clojure programming language and its key features. It discusses Clojure's dynamic and functional nature, its use of immutable data and state management via atoms, refs, and agents. It also covers Clojure's interactive development environment via the REPL, its treatment of code as data, and how functions and macros are defined. Examples are provided of Clojure code for Conway's Game of Life.
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Cracking clojure
- 2. 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
- 3. 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
- 4. Primitives 4
- 5. Collections 5
- 6. Sequences 6
- 7. Sequences 6
- 8. Functions 7
- 9. Functions 7
- 10. Functions 7
- 11. Compiler 8
- 12. Casting spells 9
- 13. Creating functions 10
- 14. Creating functions 10
- 15. Creating functions 10
- 16. Creating functions 10
- 17. Creating functions 10
- 18. An example... 11
- 19. map 12
- 20. Sequence of lines 13
- 21. Sequence of files 14
- 22. Sequence of files 14
- 23. Sequence functions 15
- 24. You 16
- 25. Lazy sequences 17
- 26. 18
- 27. 18
- 28. Power 19
- 29. Objects 20
- 30. Maps as cheap objects 21
- 31. Records 22
- 32. Java package 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
- 33. Java package 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
- 34. Data interfaces 24
- 35. Data interfaces 24
- 36. Data interfaces 25
- 37. Data - Clojure vs Java 26
- 38. Data - Clojure vs Java 26
- 39. Polymorphism 27
- 40. Generic access FTW 28
- 41. Multimethods 29
- 42. Multimethod dispatch 30
- 43. Protocols 31
- 44. State 32
- 45. Atoms 33
- 46. Refs 34
- 47. Agents 35
- 48. Destructuring 36
- 49. for comprehensions 37
- 50. for comprehensions 37
- 51. Macros 38
- 52. Macros 39
- 53. Review CONCURRENCY HOST DATA CODE 40
- 54. Review CONCURRENCY HOST DATA CODE primitives 40
- 55. Review CONCURRENCY HOST DATA CODE collections primitives 40
- 56. Review CONCURRENCY HOST sequences DATA CODE collections primitives 40
- 57. Review CONCURRENCY HOST laziness sequences DATA CODE collections primitives 40
- 58. Review CONCURRENCY HOST laziness sequences FP DATA CODE collections primitives 40
- 59. Review CONCURRENCY HOST laziness sequence library sequences FP DATA CODE collections primitives 40
- 60. Review CONCURRENCY HOST laziness sequence library sequences FP records types DATA CODE collections primitives 40
- 61. Review CONCURRENCY HOST laziness sequence library sequences multimethods FP protocols records types DATA CODE collections primitives 40
- 62. Review refs agents atoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA CODE collections primitives 40
- 63. Review refs agents atoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA CODE collections primitives destructuring 40
- 64. Review refs agents atoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA macros CODE collections primitives destructuring 40
- 65. Review refs agents atoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA macros CODE metadata collections primitives destructuring transients 40
- 66. Review refs agents atoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types DATA macros CODE metadata collections namespaces primitives destructuring transients 40
- 67. Review refs agents atoms CONCURRENCY HOST state laziness sequence library sequences multimethods FP protocols records types recursion DATA macros CODE metadata collections namespaces primitives destructuring transients 40
- 68. Review refs agents atoms 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
- 69. Review futures promises refs agents atoms 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
- 70. Conway's Life Life's 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
- 73. 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