OOP and FP: Bridging the Gap

Transition to functional programming. Gently.

Transcript

1. OOP and FP: Bridging the Gap Damir Zekić
 @sidonath
2. “A man who knows two languages is worth two men.” ‒ French Proverb
3. “Those who know nothing of foreign languages
 know nothing of their own.” ‒ Johann Wolfgang von Goethe
4. “A great programmer might be ten
 or a hundred times as productive as an ordinary one” ‒ Paul Graham
5. “Still, I don't think it's a stretch to believe this data
 shows 5:1 or 10:1 productivity differences between programmers.” ‒ Joel Spolsky
6. What Can We Learn From FP? Increase in productivity Concurrency safety
7. Functional Programming
 Is Getting Mainstream
8. Indicators
9. Indicators People talk about FP at conferences
10. Indicators People talk about FP at conferences Real-world applications built with FP languages
11. Indicators People talk about FP at conferences Real-world applications built with FP languages OOP languages are getting FP features
12. Sceptics Say…
13. Sceptics Say… Functional programming is like jetpack
14. Sceptics Say… Functional programming is like jetpack FP is only for academia
15. Sceptics Say… Functional programming is like jetpack FP is only for academia It's another tool
16. Sceptics Say… Functional programming is like jetpack FP is only for academia It's another tool … it's weird
17. Real-world Apps Built with FP Pandoc: Universal markup converter Converts from: Markdown, HTML, LaTeX, Media Wiki markup… Converts to: HTML, docx, ODT, EPUB, LaTeX, PDF, Markdown… — https://github.com/jgm/pandoc/
18. Real-world Apps Built with FP "Most of SoundCloud's products are written in Scala, Clojure, or JRuby."
 — https://developers.soundcloud.com/blog/building-products-at-soundcloud-part-1-dealing-with-the-monolith
19. Real-world Apps Built with FP "Scala is one of the main application programming
 languages used at Twitter. […] Our use of Scala is mainly
 for creating high volume services that form distributed systems"
 — http://twitter.github.io/effectivescala/
20. Real-world Apps Built with FP "We do tens of millions of RPC calls every day. […] Erlang makes
 writing those kinds of servers just ridiculously simple. I would
 never write a server like that in any other languages, Erlang
 is so perfect for that."
 — http://www.infoq.com/interviews/erlang-and-github
21. Can I Build Me Some Web Apps? Om
22. Nothing can prepare you
 for functional programming (except programming functionally)
23. … so you better get started
24. Basics of FP Functions as first-class citizens Working with and writing higher-order functions
25. A Simple Task Given a list of cart item objects (product, price, quantity),
 calculate a total price for the cart
26. JavaScript: Imperative var i, total = 0; ! for (i = 0; i < cartItems.length; i++) { total += cartItems[i].price * cartItems[i].quantity; } ! alert(total);
27. JavaScript: ES5 style var total = cartItems .map(function(cartItem) { return cartItem.price * cartItem.quantity; }) .reduce(function(sum, subtotal) { return sum + subtotal; }, 0); ! alert(total);
28. JavaScript: ES6* style var total = cartItems .map(cartItem => cartItem.price * cartItem.quantity) .reduce((sum, subtotal) => sum + subtotal, 0); ! alert(total); ! ! ! ! * May require ES6 transpiler https://github.com/google/traceur-compiler
29. C#: Imperative var total = 0m; ! foreach (var cartItem in cartItems) { total += cartItem.Price * cartItem.Quantity; } ! Console.WriteLine(total);
30. C#: Functional var total = cartItems .Select(cartItem => cartItem.Price * cartItem.Quantity) .Aggregate(0m, (sum, subtotal) => sum + subtotal); ! Console.WriteLine(total);
31. Ruby: Imperative total = 0 ! cart_items.each do |cart_item| total += cart_item.price * cart_item.quantity end ! puts total
32. Ruby: Functional total = cart_items. map { |cart_item| cart_item.price * cart_item.quantity }. reduce(0) { |sum, subtotal| sum + subtotal } ! puts total
33. Ruby: Functional #2 total = cart_items. map { |cart_item| cart_item.price * cart_item.quantity }. reduce(0, :+) ! puts total !
34. Other FP Language Features Currying, partial application and composition Pattern matching Algebraic types: "product" (record) and "sum" (union) types Immutability and many more…
35. Become a Better Programmer in 3 Steps 1. Write code in functional style in your language to grasp the concepts 2. Read "Why Functional Programming Matters"
 http://www.cs.kent.ac.uk/people/staff/dat/miranda/whyfp90.pdf 3. Learn a functional programming language
36. Crossing the Bridge JavaScript → ClojureScript C# → F# Java → Scala Ruby → Elixir
37. F# let total = cartItems |> List.map (fun ci -> ci.Price * decimal ci.Quantity) |> List.fold (+) 0M ! printfn "%M" total
38. Thank you! Q&A Damir Zekić
 @sidonath Slides published at: http://bit.ly/fp-bridge