BRUG - Hello, Scala
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Introduction to functional programming for the Bristol Ruby User Group
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BRUG - Hello, Scala
- 1. Hello, Scala Timothy Perrett BRUG, October 2011 software. done right.
- 2. About Me Author of Lift in Action Coding Scala since 2007 (its awesome) Background in both dynamic and statically typed languages Manufacturing and marketing automation is my day job http://manning.com/perrett/ software. done right.
- 4. A statically typed, hybrid object- functional programming language software. done right.
- 5. functional programming is... software. done right.
- 6. …programming with functions software. done right.
- 7. A program is software. done right.
- 8. a single, referentially transparent expression software. done right.
- 9. An expression is software. done right.
- 10. a combination of sub expressions, using the constructs of a language. It evaluates to a result. software. done right.
- 11. a referentially transparent expression... software. done right.
- 12. …is an expression that can be replaced directly by its result without affecting the program operation. i.e. no side-effects software. done right.
- 13. a side-effect is... software. done right.
- 14. for example: I/O variable mutation throwing exceptions software. done right.
- 15. a function is... software. done right.
- 16. a relation between every value of type A to exactly one value of type B. (given f: A => B) software. done right.
- 17. functional programming gives you… software. done right.
- 18. modularity and compositionality software. done right.
- 19. fpis a style, not a language software. done right.
- 20. and static typing?... software. done right.
- 21. well, ruby is… software. done right.
- 22. duck typed… software. done right.
- 23. …scala is statically typed software. done right.
- 24. ”…types save you from errors, give you useful program documentation and act as a safety net for refactoring…" Martin Odersky software. done right.
- 25. code samples software. done right.
- 26. nums = [1,2,3,4] nums.select do |n| n % 2 == 0 end software. done right.
- 27. valnums = Seq(1,2,3,4) nums.filter { n => n % 2 == 0 } software. done right.
- 28. valnums = Seq(1,2,3,4) nums.filter(_ % 2 == 0) software. done right.
- 29. useful data types software. done right.
- 30. valfoo = Option("thing") //=>Some(“thing”) val bar = Option(null) //=> None software. done right.
- 31. foo = … // comes from user input if foo == nil then // do something with foo end software. done right.
- 32. // where foo is user input Option(foo).map(x => …) software. done right.
- 33. implicit pimps software. done right.
- 34. class Foo(word: String) { def say = println(word) } implicit def strToFoo(in: String): Foo … “word”.say software. done right.
- 35. supports DSLs… software. done right.
- 36. take 2 pills and call me in the morning take(2.pills).and(call).me(in).the(morning) software. done right.
- 37. blistering performance software. done right.
- 38. Performance 60 50 40 30 Scala Ruby (Jruby) Ruby 1.9 20 10 0 Scala Ruby (Jruby) Ruby 1.9 source: http://shootout.alioth.debian.org/ software. done right.
- 39. heaps more awesome Concurrency abstractions Parallel data structures BDD & property testing Ad-hoc polymorphism Higher-kinded types Existential types software. done right.
- 40. Questions? twitter.com/timperrett Lift in Action github.com/timperrett manning.com/perrett/ blog.getintheloop.eu software. done right.
Notes de l'éditeur
- Afternoon everyone; welcome to this talk on Lift the web framework for Scala.
- Before we get started with the presentation here’s a little information about me.** CLICK **I’ve been working on the lift project for around 2.5 years and using it in production for about 3 years. I work on a lot of different aspects of the framework but I am particularly interested in localization and process abstractions within Lift core. I also use Lift during my day job as do most of the other committers so in that sense we are not just making a framework for the sake of it, what we put into lift are real-life abstractions from the field ** CLICK **I am the author of a new book called Lift in Action, available on Manning publications. At the end of this talk I will be giving away a 40% discount for people who are interested in learning more about Lift.** CLICK **CodingScala since the end of 2007 – both with Lift and standalone Scala applications** CLICK **Before I came to the scala community I was working extensively with Ruby, along with Rails. Before that I was coding a lot of Objective-C and Java for desktop applications. ** CLICK **My day job is producing interesting sections of middleware for marketing automation and cross-media marketing for a division of Xerox corporation.** CLICK **
- ModularityThe degree to which the parts can be separated and recombined.CompositionalityUnderstand the parts, and the connections, and you understand the whole.
- creating a block (Ruby’s name for a closure) which takes a single parameter and passes it to the built-in puts method. This block is then passed as an object to the each method of class Array, which calls the block once for each element in series
- creating a block (Ruby’s name for a closure) which takes a single parameter and passes it to the built-in puts method. This block is then passed as an object to the each method of class Array, which calls the block once for each element in series