Functional Programming is the new black

Transcript

1. Sunday, 7 October 12
2. Plan B Sunday, 7 October 12
3. Why functional is the new black Elise Huard @elise_huard JSConf EU 2012 Sunday, 7 October 12
4. Why functional is the new black Elise Huard @elise_huard JSConf EU 2012 Sunday, 7 October 12
5. Why functional is the new black Elise Huard @elise_huard JSConf EU 2012 Sunday, 7 October 12
6. Sunday, 7 October 12
7. λ λ Sunday, 7 October 12
8. λ λ Sunday, 7 October 12
9. Sunday, 7 October 12
10. Sunday, 7 October 12
11. It’s all functions Sunday, 7 October 12
12. It’s all functions no global variables or global state Sunday, 7 October 12
13. It’s all functions no global variables or global state no side-effects Sunday, 7 October 12
14. It’s all functions no global variables or global state no side-effects no destructive updates Sunday, 7 October 12
15. function Person(gender) { this.gender = gender; } Person.prototype.sayGender = function() { console.log(this.gender); }; var person1 = new Person('Male'); var genderTeller = person1.sayGender; Sunday, 7 October 12
16. Sunday, 7 October 12
17. Some “patterns” Sunday, 7 October 12
18. Higher order functions Sunday, 7 October 12
19. Taking functions as arguments Sunday, 7 October 12
20. input.change(function(event) {...}); app.get('/', function(req, res) { ...}); Sunday, 7 October 12
21. returning functions Sunday, 7 October 12
22. var validate = function(validationFunction) { return function(field) { var isError, errorMessage = validationFunction(field); return (isError,errorMessage); } } var requiredField = validate(function(field) { var errorMessage = null; if (!field) { errorMessage = "should have a field" } return [!field, errorMessage]; }) Sunday, 7 October 12
23. Utilities Sunday, 7 October 12
24. [1,3,5].map(function(x) {return x+1 }); http://underscorejs.org/ _.map([1,2,3], function(x) {return x+1}); http://osteele.com/sources/javascript/functional/ map('x+1', [1,2,3,4]) Sunday, 7 October 12
25. for (var i = 0; i < array.length; i++) doSomething(array[i]); // => map for (var i = 0; i < array.length; i++) { if (array[i]%2 == 0) doSomething(array[i]); } // => filter var sum = 0; for (var i = 0; i < array.length; i++) { sum += array[i]; } // => reduce/foldl http://notes-on-haskell.blogspot.co.uk/2007/02/whats-wrong-with-for-loop.html Sunday, 7 October 12
26. Currying Sunday, 7 October 12
27. var phoneListing = function(name,home) { return name + “ - “ + phone; } listing(“Sam”,”012345678”); listing(“Sam”); // => undefined Sunday, 7 October 12
28. // getLocalArgs() = Array.prototype.slice.call(arguments) function partial(f) { var args = getLocalArgs(), givenArgs = args.slice(1); return function() { var remainingArgs = getLocaLArgs(); return f.apply(this, givenArgs.concat(remainingArgs)); } } var samsPartner= partial(phoneListing, ”Sam”); samsPartner(“0999999999”); // => “Sam - 0999999999” Sunday, 7 October 12
29. Monads Sunday, 7 October 12
30. Sunday, 7 October 12
31. // make a monadic value (“return”) var makeMonadicValue = function(value) { return function(state) { return {value: value, state: state}; } } Sunday, 7 October 12
32. // make a very simple monadic value var makeMonadicValue = function(value) { return function() { return value; } } Sunday, 7 October 12
33. // make a monadic value (“return”) var makeMonadicValue = function(value) { return function(state) { return {value: value, state: state}; } } Sunday, 7 October 12
34. // Joe is in the kitchen var mv = makeMonadicValue("Joe"); mv(10); // => {value: "Joe", state: 10} Sunday, 7 October 12
35. // bind to a function var bindToFunction = function(mv, f) { return function(state) { var monadOutput = mv(state), value = monadOutput.value, newState = monadOutput.state; return (f(value))(newState); } } Sunday, 7 October 12
36. // you could act on the value directly var addPerson = function(value, name) { return value + " and " + name; } // but here's the monadic way to do it var mAddPerson = function(mv, name) { return bindToFunction(mv, function(value) { return makeMonadicValue(value + " and " + name); }) } Sunday, 7 October 12
37. (mAddPerson(mv, "Tom"))(10); // => {value:"Joe and Tom", state: 10} Sunday, 7 October 12
38. // you can act on state var takeYoghurt = function(state) { return state - 1; } var mTakeYoghurt = function(mv) { return bindToFunction(mv, function(value) { return function(state) { return {value: value, state: state-1}; } }) } (mTakeYoghurt(mv))(10); // => {value: "Joe", state: 9 } Sunday, 7 October 12
39. (mTakeYoghurt( (mAddPerson( (mTakeYoghurt( (mAddPerson (mv,"Tom") ))), "Shelley")))) (10); // => { value: 'Joe and Tom and Shelley', state: 8 } http://www.infoq.com/presentations/Why-is-a-Monad-Like-a- Writing-Desk Sunday, 7 October 12
40. Lazy evaluation (?) Sunday, 7 October 12
41. The Good Sunday, 7 October 12
42. Easier to debug Sunday, 7 October 12
43. Easier to test Sunday, 7 October 12
44. Easier to refactor Sunday, 7 October 12
45. Parallelization (?) Sunday, 7 October 12
46. Hard? Sunday, 7 October 12
47. <rant> Sunday, 7 October 12
48. "the greatest single programming language ever designed" - Alan Kay, on Lisp, the 70s Sunday, 7 October 12
49. “Object-oriented programming (...) allows software structure to be based on real-world structures, and gives programmers a powerful way to simplify the design and construction of complex programs. - D. Gelernter, the 80s Sunday, 7 October 12
50. Sunday, 7 October 12
51. Software is hard Sunday, 7 October 12
52. Sunday, 7 October 12
53. </rant> Sunday, 7 October 12
54. But: Sunday, 7 October 12
55. Thank you. Elise Huard @elise_huard Sunday, 7 October 12