The ideas of Clojure - Things I learn from Clojure

A basic Clojure introduction.

Transcript

1. THE IDEAS OF CLOJURE JCConf 2015/12/04 Randy Lien Things I learn from Clojure
2. About me @randylien UI Engineer #WebAppsRocks #JavaScriptIsNotSoJavaScript #WhenIsNextReactJS.TwMeetup #clojurians.tw@facebook
3. Survey! • Heard Clojure? • Clojure developer? • Enjoy Java development?
4. “I don’t know Java.” – Speaker
6. History of programming languages
7. LISP
8. Clojure ?
9. React.js Conf 2015
10. Tapestry Dude - https://goo.gl/R5m3am (CC BY-SA 2.0) The Creator of Clojure
 Rich Hickey
11. "Hickey is the new Messiah of software development. Watch and listen to his talks, and you will understand." – http://bepsays.com/2014/07/08/how-rich-is-rich-hickey/
12. Few ideas I want to share
13. Philosophy
14. Philosophy Focus Simplicity Empowerment Pure functions Expressive Practical Clarity
 Consistency Separation 
 of 
 concerns Concise Direct Interop - The Joy of Clojure
15. Philosophy - Simplicity • Pure functions • Immutable • Simple abstractions • defprotocol • deftype
16. Philosophy - Focus • Syntax will not bother you • Consistency • Dynamic System • Almost everything defined in Clojure can be redefined (Even while program is running) • Use Macro you can build anything you want to do
17. Philosophy - Empowerment • Use Java Virtual Machine • Java is mature and has many libraries • JavaScript is everywhere (ClojureScript)
18. Consistency
19. Syntax does matter
20. Java + Python + JavaScript ?
21. JaPythonScript?
22. Data Types • Integers - 123 • Doubles - 1.23 • Ratios - 1/23 • Strings - "JCConf" • "Double Quotes Only" • Characters - \J \C
23. Data Types (cont.) • Symbols - bar • Keywords - :foo • Booleans - true false • Null - nil • Regex - #"[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]+"
24. Data Structure • Lists - (1 2 3) • Prepend • Vectors - [1 2 3] • Zero indexed. Append • Maps - {:a 1, :b 2, :c "3"} • Key-value pair • Comma will be ignored • Sets - #{1 2 3} • Unique. Unordered
25. function definition
26. function definition doc string
27. Clojure • (+ 1 2) • (+ 1 2 3) • (into [] 2) General • 1 + 2 • 1 + 2 + 3 • [].push(2)
29. Use host libraries - Java
30. Use host libraries - JavaScript
31. DEMO
32. functions & composition
33. functions & composition • map, reduce, filter • partial, comp • iterate • repeat, repeatedly • Many built-in functions and you don’t need to create.
 Just compose it!
34. DEMO
35. Values
36. Values should be… • Value! • operated by functions • time-relative • Immutable
37. Why Immutable?
38. Why mutable?
39. Why mutable? • Limitations of early computers: Small RAM and disk • New information replaces old
40. Why immutable? • No resource limitation • Persistent data structure • Record - Share the same data • Key to do functional programming • No side effect • atom is mutable
41. REPL Driven Development
42. REPL ? • Read–Eval–Print Loop • nREPL (network REPL) • Good for doing TDD • clojure.test • ClojureScript - Browser can connect to nREPL
43. REPL DEMO - ClojureScript
44. REPL DEMO - Clojure
45. Tooling Eco-system
46. Clojars emacs LightTable
47. Leiningen
48. Summary
49. Summary • Clojure is a practical functional programming language • Java and JavaScript are two major languages and Clojure and ClojureScript can run on them • Using REPL in your TDD practices would be helpful • Pure functions and Immutable data structure can make your system stable and easy to reason about
50. Summary (cont.) • Clojure has much better tooling and keep improving it • ClojureScript is hotter than Clojure! • Many companies are using Clojure • booking.com, Yahoo, Puppet, Walmart, twitter, heroku, nubank…etc • STM, transducer, core.asyn
51. If you want to know more… • Living Clojure • The Joy of Clojure • ClojureScript Unraveled • Clojure Applied • Clojure for the Brave and True
52. Online resource • http://www.tryclj.com/ • http://www.4clojure.com/
54. Worth to watch • Simple Made Easy • Clojure Made Simple • The Value of Values • The Language of the System
55. Thanks