SwiftLille Meetup #4 - @kamidude - Bool Tricks

Booleans - Logic tips and tricks for a better code : Comment utiliser les booleens pour simplifier votre code, le rendre plus lisible et plus robuste ? Comment les reconnaitre, les recombiner et aussi ne pas s’en servir quand il ne faut pas.
🎤Présenté par Jérémie Girault, Founder & CTO @ Hubvisor

Transcript

1. Bool Tricks @kamidude
2. Agenda @kamidude
3. Agenda false @kamidude
4. Agenda true false @kamidude
5. Agenda true @kamidude Bool Basics
6. Agenda @kamidude Bool Basics Advanced tricks
7. Bool Basics @kamidude
8. Basics 〉Priorities ❗ @kamidude
9. Basics 〉Priorities let E = !A || B && C || D @kamidude
10. Basics 〉Priorities let E = !A || B && C || D let E = ((!A) || (B && C)) || D @kamidude
11. Basics 〉ShortCircuits ⚡ @kamidude
12. Basics 〉ShortCircuits func doThis () -> Bool { print("doThis") return false } func doThat () -> Bool { print("doThat") return false } let x = doThis() && doThat() print(x) @kamidude
13. public static func && (lhs: Bool, rhs: @autoclosure () throws -> Bool) rethrows -> Bool
 public static func || (lhs: Bool, rhs: @autoclosure () throws -> Bool) rethrows -> Bool Basics 〉ShortCircuits func doThis () -> Bool { print("doThis") return false } func doThat () -> Bool { print("doThat") return false } let x = doThis() && doThat() print(x) @kamidude
14. Basics 〉Extract names @kamidude
15. Basics 〉Extract names func canEnterRollercoaster(age: UInt, size: UInt) -> Bool { age >= 15 && size > 150 } @kamidude
16. Basics 〉Extract names func canEnterRollercoaster(age: UInt, size: UInt) -> Bool { age >= 15 && size > 150 } func canEnterRollercoaster(age: UInt, size: UInt) -> Bool { let isTallEnough = size > 150 let isOldEnough = age >= 15 return isTallEnough && isOldEnough } @kamidude
17. Basics 〉Logic Semantic Only @kamidude
18. Basics 〉Logic Semantic Only @kamidude struct AppleCard { let isMan: Bool func getCreditScore () -> Double { isMan ? 100 : 50 } }
19. Basics 〉Logic Semantic Only @kamidude struct AppleCard { let isMan: Bool func getCreditScore (useNewAlgorithm: Bool) -> Double { let initialValue: Double = isMan ? 100 : 50 return useNewAlgorithm ? random * initialValue : initialValue } }
20. Basics 〉Logic Semantic Only @kamidude struct AppleCard { let isMan: Bool func getCreditScore (algorithm: Algorithm) -> Double { let initialValue: Double = isMan ? 100 : 50 switch (algorithm) { case .old: return random * initialValue case .new: return initialValue } } }
21. Basics 〉Linearize code @kamidude
22. Basics 〉Linearize code @kamidude func performActionIfAllowed (action: () -> Void) { if (isLoggedIn) { if (hasAccessRights) { action() } else { showError("User has not access rights !") } } else { showError("User is not logged in !") } }
23. Basics 〉Linearize code @kamidude func performActionIfAllowed (action: () -> Void) { if (isLoggedIn) { if (hasAccessRights) { action() } else { showError("User has not access rights !") } } else { showError("User is not logged in !") } } func performActionIfAllowed (action: () -> Void) { guard isLoggedIn else { return showError("User is not logged in !") } guard hasAccessRights else { return showError("User has not access rights !") } action() }
24. Advanced tricks @kamidude
25. Advanced 〉Operators Symbol Name Swift @kamidude
26. Advanced 〉Operators Symbol Name Swift ¬ Négation ! @kamidude
27. Advanced 〉Operators Symbol Name Swift ¬ Négation ! ∧ Conjonction && @kamidude
28. Advanced 〉Operators Symbol Name Swift ¬ Négation ! ∧ Conjonction && ∨ Disjonction || @kamidude
29. Advanced 〉Operators Symbol Name Swift 㱻 Equivalence ¬ Négation ! ∧ Conjonction && ∨ Disjonction || @kamidude
30. Advanced 〉Operators Symbol Name Swift 㱻 Equivalence == ¬ Négation ! ∧ Conjonction && ∨ Disjonction || @kamidude
31. Advanced 〉Operators Symbol Name Swift 㱻 Equivalence == ¬ Négation ! ∧ Conjonction && ∨ Disjonction || ⊻ Disjonction exclusive @kamidude
32. Advanced 〉Operators Symbol Name Swift 㱻 Equivalence == ¬ Négation ! ∧ Conjonction && ∨ Disjonction || ⊻ Disjonction exclusive != @kamidude
33. Advanced 〉Operators Symbol Name Swift 㱺 Implication 㱻 Equivalence == ¬ Négation ! ∧ Conjonction && ∨ Disjonction || ⊻ Disjonction exclusive != @kamidude
34. Advanced 〉Implication ☔ @kamidude
35. Advanced 〉Implication A B A㱺B 0 0 1 0 1 1 1 0 0 1 1 1 @kamidude
36. Advanced 〉Implication A B A㱺B 0 0 1 0 1 1 1 0 0 1 1 1 A 㱺 B 㱻 ¬B 㱺 ¬A @kamidude
37. Advanced 〉Implication A B A㱺B 0 0 1 0 1 1 1 0 0 1 1 1 A 㱺 B 㱻 ¬A ∨ B 㱻 ¬B 㱺 ¬A @kamidude
38. Advanced 〉Implication extension Bool { func implies (_ other: @autoclosure () -> Bool) -> Bool { return !self || other() } } @kamidude
39. struct User { let age: UInt let hasParentsAuthorization: Bool let hasActiveSubscription: Bool } Advanced 〉Implication @kamidude
40. struct User { let age: UInt let hasParentsAuthorization: Bool let hasActiveSubscription: Bool } func isAdmissible (user: User) -> Bool { if (user.hasActiveSubscription) { if (user.age < 18) { return user.hasParentsAuthorization } else { return true } } else { return false } } Advanced 〉Implication @kamidude
41. struct User { let age: UInt let hasParentsAuthorization: Bool let hasActiveSubscription: Bool } func isAdmissible (user: User) -> Bool { if (user.hasActiveSubscription) { if (user.age < 18) { return user.hasParentsAuthorization } else { return true } } else { return false } } extension User { var isJuvenile: Bool { age < 18 } } Advanced 〉Implication @kamidude
42. struct User { let age: UInt let hasParentsAuthorization: Bool let hasActiveSubscription: Bool } func isAdmissible (user: User) -> Bool { if (user.hasActiveSubscription) { if (user.age < 18) { return user.hasParentsAuthorization } else { return true } } else { return false } } extension User { var isJuvenile: Bool { age < 18 } } func isAdmissible (user: User) -> Bool { return user.hasActiveSubscription && user.isJuvenile.implies(user.hasParentsAuthorization) } Advanced 〉Implication @kamidude
43. Advanced 〉Transformations ¬¬A 㱻 A @kamidude Double Negation
44. Advanced 〉Transformations Usage let canSeeMovie = !(age < 18) guard (canSeeMovie) else { return } @kamidude
45. Advanced 〉Transformations Usage let canSeeMovie = !(!(age >= 18))
 guard (canSeeMovie) else { return } @kamidude
46. Advanced 〉Transformations Usage let canSeeMovie = age >= 18
 guard (canSeeMovie) else { return } @kamidude
47. Advanced 〉Transformations (A∨B)∧C 㱻 (A∧C)∨(B∧C)
 (A∧B)∨C 㱻 (A∨C)∧(B∨C) @kamidude Distributivity
48. Advanced 〉Transformations Usage if (shouldDisplayData && (hasLocalData || isNetworkAvailable)) { // show results screen } @kamidude
49. Advanced 〉Transformations Usage if (shouldDisplayData && (hasLocalData || isNetworkAvailable)) { // show results screen } let shouldDisplayLocalData = shouldDisplayData && hasLocalData let shouldDisplayRemoteData = shouldDisplayData && isNetworkAvailable if (shouldDisplayLocalData || shouldDisplayRemoteData) { // show results screen } @kamidude
50. Advanced 〉Transformations ¬(A∨B) 㱻 ¬A∧¬B
 ¬(A∧B) 㱻 ¬A∨¬B @kamidude De Morgan
51. Advanced 〉De Morgan A B ¬(A∨B) ¬A∧¬B 0 0 1 1 0 1 0 0 1 0 0 0 1 1 0 0 A B ¬(A∧B) ¬A∨¬B 0 0 1 1 0 1 1 1 1 0 1 1 1 1 0 0 Proof @kamidude
52. Advanced 〉Transformations (!(X1 || X2) || (X3 && X4)) && (!X1 || X2) @kamidude FNC && FND
53. Advanced 〉Transformations (!(X1 || X2) || (X3 && X4)) && (!X1 || X2) @kamidude 㱻 (!X1 || X3) && (!X1 || X4) && (!X2 || X3) && (!X2 || X4) && (!X1 || X2) FNC && FND
54. Advanced 〉FNC && FND @kamidude Use Case
55. Advanced 〉FNC && FND @kamidude func refundCustomerIfNeeded () { if ((!isEnterprise && !isCivil && hasFreePass) && (now < billSentTime + refundExpirationInterval) && (billHasBeenPosted || billHasBeenEmailed || billHasBeenGivenInHand) && hasBillBeenPaid && customerHasSentHandwrittenLetter) { refundNow() } else { showError("An Unknown error happened, please try again later") } } Use Case
56. Advanced 〉FNC && FND @kamidude func refundCustomerIfNeeded () { let isCustomerBillable = isEnterprise || isCivil || !hasFreePass let hasCustomerBeenSentBill = billHasBeenPosted || billHasBeenEmailed || billHasBeenGivenInHand let refundPeriodExpired = now < billSentTime + refundExpirationInterval guard isCustomerBillable else { return showError("The customer did not need to pay anything !") } guard hasCustomerBeenSentBill else { return showError("The customer has not been sent a bill yet !") } guard !refundPeriodExpired else { return showError("The refund period has expired !") } guard hasBillBeenPaid else { return showError("The bill has not been paid, no refund can be done yet") } guard customerHasSentHandwrittenLetter else { return showError("The customer must send a handwritten letter") } refundNow() } func refundCustomerIfNeeded () { if ((!isEnterprise && !isCivil && hasFreePass) && (now < billSentTime + refundExpirationInterval) && (billHasBeenPosted || billHasBeenEmailed || billHasBeenGivenInHand) && hasBillBeenPaid && customerHasSentHandwrittenLetter) { refundNow() } else { showError("An Unknown error happened, please try again later") } } Use Case
57. Recap @kamidude
58. Recap @kamidude Linearize code
59. Recap @kamidude Linearize code Extract and name terms
60. Recap @kamidude Linearize code Use Bools for logic Extract and name terms
61. Recap @kamidude Linearize code Use Bools for logic Extract and name terms Transform and optimize expressions
62. Recap @kamidude Distributivity Linearize code Use Bools for logic Extract and name terms Transform and optimize expressions
63. Recap @kamidude Distributivity Linearize code Use Bools for logic Extract and name terms Transform and optimize expressions De Morgan
64. Recap @kamidude Distributivity Linearize code Use Bools for logic Extract and name terms Transform and optimize expressions De Morgan FNC && FND
65. Recap @kamidude Distributivity Linearize code Use Bools for logic Extract and name terms Transform and optimize expressions De Morgan FNC && FND Theory is fun, go read wikipedia
66. Thank you ! @kamidude