OOP is dead only if FP is dead

It is common to see Functional Programming (FP) presented as the opposite of Object-oriented Programming (OOP). These two programming paradigms have important differences, but they can share a lot in common, so they are not in direct opposition. In this talk, Andre will explore the gray area between OOP and FP, with code samples in JavaScript, TypeScript, and Haskell, kept easy enough enough for any programmer to follow.

Transcript

1. OOP is dead 
 only if FP is dead @andrestaltz
2. Is object-oriented programming fundamentally different or superficially different to functional programming?
3. OOP FP
4. Closures Objects Immutability Mutation Assignment
 syntax Assignment
 semantics Typed Dynamic Evaluate Execute
5. Evaluate Execute
6. Evaluate Execute Calculate the value of an expression Perform a sequence of get/set actions
7. Evaluate Execute Calculate the value of an expression Perform a sequence of get/set actions Imperative Functional
8. Evaluate Execute (weight => height => weight / 
 (height * height * 0.01 * 0.01) )(70)(177) var weight = 70; var height = 177; var bmi = weight; bmi /= height; bmi /= height; bmi /= 0.01; bmi /= 0.01;
9. Evaluate Execute Foundation is Lambda calculus Foundation is
 Random access machine
10. Closures Objects
11. Closures Objects Put data in an object, attach methods to the object Put data in a closure, functions refer to the closure
12. Closures Objects const greeter = { isFemale: false, greet(name) { return this.isFemale ? "Hi Ms. " + name : "Hi Mr. " + name; } }; const greet = (isFemale => name => isFemale ? "Hi Ms. " + name : "Hi Mr. " + name )(false);
13. Closures Objects const greeter = { // ... }; greeter.greet.bind({isFemale: true})('Lisa'); Advantage: allows changing the this object for a method.
14. Closures Objects const greeter = { // ... }; greeter.greet.bind({isFemale: true})('Lisa'); Advantage: allows changing the this object for a method. Disadvantage: allows changing the this object for a method.
15. Immutability Mutation
16. Immutability Mutation
17. Immutability Mutation final String s = "ABC"; s.toLowerCase(); Java
18. Immutability Mutation Haskell import Data.Char str1 = "ABC" str2 = map toLower str1
19. Immutability Mutation Haskell import Data.IORef f :: Num a => a -> IO a f x = do y <- newIORef 5 -- :: IORef Int writeIORef y 10 val <- readIORef y -- :: Int return 2 * val
20. Immutability Mutation Haskell import Data.STRef import Control.Monad.ST f :: Num a => a -> a f x = runST $ do y <- newSTRef 5 -- :: STRef Int writeSTRef y 10 val <- readSTRef y -- :: Int return 2 * val
21. Assignment
 syntax Assignment
 semantics
22. Assignment
 syntax Assignment
 semantics Haskell do text <- readFile "foo" writeFile "bar" text readFile "foo" >>= writeFile "bar"
23. Assignment
 syntax Assignment
 semantics Haskell do text <- readFile "foo" writeFile "bar" text readFile "foo" >>= writeFile "bar"
24. Assignment
 syntax Assignment
 semantics JavaScript var text = fs.readFileSync('foo'); fs.writeFileSync('bar', text);
25. Assignment
 syntax Assignment
 semantics strongConnect v graph index stack indices lowlinks output = do i <- readSTRef index modifySTRef' indices (I.insert v i) modifySTRef' lowlinks (I.insert v i) modifySTRef' index (+1) push stack v forM_ (graph A.! v) $ \w -> do wIndex <- I.lookup w <$> readSTRef indices if isNothing wIndex then do strongConnect w graph index stack indices lowlinks output vLowLink <- fromJust . I.lookup v <$> readSTRef lowlinks wLowLink <- fromJust . I.lookup w <$> readSTRef lowlinks modifySTRef' lowlinks (I.insert v $ min vLowLink wLowLink) else do wOnStack <- elem w <$> readSTRef stack when wOnStack $ do vLowLink <- fromJust . I.lookup v <$> readSTRef lowlinks modifySTRef' lowlinks (I.insert v $ min vLowLink (fromJust wIndex)) vLowLink <- fromJust . I.lookup v <$> readSTRef lowlinks vIndex <- fromJust . I.lookup v <$> readSTRef indices when (vLowLink == vIndex) $ do scc <- addSCC v [] stack modifySTRef' output (scc:) http://vaibhavsagar.com/blog/2017/05/29/imperative-haskell/
26. Typed Dynamic
27. Typed Dynamic Clojure (FP) Python (OOP) Haskell (FP) Java (OOP)
28. Typed Dynamic Is x => 2 * x pure?
29. Typed Dynamic Is x => 2 * x pure? const double = x => 2 * x; const lol = {}; lol.valueOf = Math.random; double(lol); // 0.21666564647375441 double(lol); // 1.4260443726695509
30. Typed Dynamic Is x => 2 * x pure? const double: (x: number) => number = x => 2 * x;
31. Typed Dynamic Abstractions: solving problems on the level of ideas
32. Typed Dynamic
33. Typed Dynamic
34. Typed Dynamic Abstraction = flexibility. integers = [1, 2..] list1 = take 5 integers -- [1,2,3,4,5] list2 = take 10 integers -- [1,2,3,4,5,6,7,8,9,10] Haskell
35. Typed Dynamic In Java... Objects are concrete. Interfaces are abstract. Classes are a bit of both.
36. Typed Dynamic In Haskell... Basic types are concrete. Type classes are abstract. Abstract Data Types too.
37. Typed Dynamic Inheritance In OOP: reusability of classes (= data + methods) In FP: reusability of type classes (= functions)
38. Typed Dynamic Inheritance In OOP: reusability of classes (= data + methods) In FP: reusability of type classes (= functions)
39. Typed Dynamic Inheritance In OOP: reusability of classes (= data + methods) In FP: reusability of type classes (= functions)
40. Typed Dynamic Inheritance In OOP: reusability of classes (= data + methods) In FP: reusability of type classes (= functions)
41. Typed Dynamic Inheritance In OOP: reusability of classes (= data + methods) In FP: reusability of type classes (= functions)
42. Typed Dynamic Inheritance In OOP: reusability of classes (= data + methods) In FP: reusability of type classes (= functions)
43. Typed Dynamic Diamond problem in typed OOP Object equals() Rectangle equals() Clickable equals() Button
44. The real problem is that programmers have spent far too much time worrying about efficiency in the wrong places and at the wrong times; 
 premature optimization is the root of all evil (or at least most of it) in programming. – Donald Knuth
45. Premature concretization is the root of all complexity (or at least most of it) in programming. – André Staltz
46. Typed Dynamic Haskell can reliably do multiple inheritance.
47. Typed Dynamic Haskell can reliably do multiple inheritance.
48. Typed Dynamic JavaScript can unreliably do multiple inheritance.
49. Typed Dynamic JavaScript can unreliably do multiple inheritance. // Creating objects var o1, o2, o3, obj = multiInherit(o1={a:1}, o2={b:2}, o3={a:3, b:3}); // Setting properties obj.c = 3; // Reading properties obj.a; // 1 (inherited from o1) obj.b; // 2 (inherited from o2) obj.c; // 3 (own property) obj.d; // undefined (not found) https://stackoverflow.com/questions/9163341/multiple-inheritance-prototypes-in-javascript/31236132#31236132
50. Typed Dynamic JavaScript can unreliably do multiple inheritance. function multiInherit (...protos) { return Object.create(new Proxy(Object.create(null), { get (target, prop, receiver) { var obj = protos.find(obj => prop in obj); return obj ? Reflect.get(obj, prop, receiver) : void 0; }, set (target, prop, value, receiver) { var obj = protos.find(obj => prop in obj); return Reflect.set(obj || Object.create(null), prop, value, receiver); }, has: (target, prop) => protos.some(obj => prop in obj), ownKeys(target) { // ... }, getOwnPropertyDescriptor(target, prop) { // ... }, *enumerate (target) { yield* this.ownKeys(target); }, preventExtensions: (target) => false, defineProperty: (target, prop, desc) => false, })); }
51. Typed Dynamic Strongly typed FP Haskell
52. Haskell v1.3 Report
53. Haskell v1.3 Report
54. Evaluate Execute Calculate the value of an expression Perform a sequence of get/set actions Imperative Functional
57. OOP FP Should we mix everything?
58. OOP FP Should we mix everything? Languages should be coherent
59. Koka Typed Evaluate Immutability Assignment syntax Closures Object syntax
68. Closures Objects Immutability Mutation Assignment
 syntax Assignment
 semantics Typed Dynamic Evaluate Execute Thanks : )