The design of Clojure

An outline of how the Clojure programming language is designed to be used.

Transcript

1. The Design of Clojure Shantanu Kumar, Concur 1
2. Who am I? • Engineer @ Concur • Author of “Clojure High Performance Programming” • Open Source enthusiast: https://github.com/ kumarshantanu • @kumarshantanu on Twitter 2
3. Clojure • Created by Rich Hickey, 2007 • Eclipse Public License (OSS) • Website — https://clojure.org/ • Lisp • Functional • Hosted on JVM (and CLR, JS) 3
4. Big ideas • Pervasive immutability (Epochal time model) • First-class values • First-class functions • Performance • Host interoperability • First-class state management 4
5. –Stuart Halloway “Clojure feels like a general-purpose language beamed back from the near future.” 5
6. Getting started with Clojure http://leiningen.org/ https://learnxinyminutes.com/docs/clojure/ http://www.braveclojure.com/ https://www.4clojure.com/ 6
7. Interactive REPL 7
8. Data types • Number: 42, -5.67, 22/7 • Boolean: true, false • Character: \x, \y, \newline, \space • String: “foo”, “bar” (multi-line literals are supported) • Symbol: ‘do-something, ‘bizfn • Keyword: :red, :blue • Nothing: nil 8
9. Data structures • List: ‘(“Harry” 34 :male) — sequential access • Map: {:name “Harry” :age 34} • Set: #{:red :blue} • Vector: [“Harry” 34 :male] 9
10. Working with data structures 10
11. Functions 11
12. Code is data 12
13. Persistent Data-structures • Immutable (updates return new instances) • Structure sharing (Hash array mapped trie) • 32-way branching for O(<7) performance • Sustained performance across updates • Reference: “Ideal Hash Trees” (Phil Bagwell) 13
14. Working with collections 14
15. I want a loop! No automatic tail-call optimization 15
16. –Alan J Perlis “A language that doesn't affect the way you think about programming, is not worth knowing.” 16
17. Records 17
18. Records • Class semantics (memory layout) • Behave as maps • Immutable in the same way as maps 18
19. Protocols 19
20. Protocols • Behaviour contract • Polymorphism • Dispatch on target object type • Used as implementation details 20
21. No structural inheritance! But, there are value hierarchies Image source: https://xspblog.files.wordpress.com/2008/06/owl_yarly.jpg 21
22. Macros 22
23. Sample output 23
24. Macros • Compile-time code manipulation • Because code is data 24
25. Java interop 25
26. Concurrent execution • CPU-bound and I/O-bound thread pools • `future`: Asynchronous one-time access • `pmap`: Concurrent CPU-bound processing • `promise/deliver`: Single producer-consumer • Java’s concurrent collections considered idiomatic 26
27. Concurrency and state • Atoms — uncoordinated compare and swap • Agents — asynchronous sequential operations • Refs — Software Transactional Memory • Dynamic vars — Thread-local access 27
28. Thank you! @kumarshantanu 28