Demystify Functional Programming in Swift
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Trying to explain functional programming core concepts stripping away category theory (but with a lot of respect!)
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Demystify Functional Programming in Swift
- 1. DEMYSTIFY FUNCTIONAL PROGRAMMING IN (OR TRYING TO … 🤔) ENNIO MASI SENIOR IOS DEV @ YOOX NET-A-PORTER
- 2. IN COMPUTER SCIENCE, FP IS A PROGRAMMING PARADIGM - A STYLE OF BUILDING THE STRUCTURE AND ELEMENTS OF COMPUTER PROGRAMS - THAT TREATS COMPUTATION AS THE EVALUATION OF MATHEMATICAL FUNCTIONS AND AVOIDS CHANGING - STATE AND MUTABLE DATA. IN COMPUTER SCIENCE, FP IS A PROGRAMMING PARADIGM - A STYLE OF BUILDING THE STRUCTURE AND ELEMENTS OF COMPUTER PROGRAMS - THAT TREATS COMPUTATION AS THE EVALUATION OF MATHEMATICAL FUNCTIONS AND AVOIDS CHANGING - STATE AND MUTABLE DATA. FUNCTIONAL PROGRAMMING IN COMPUTER SCIENCE, FP IS A PROGRAMMING PARADIGM - A STYLE OF BUILDING THE STRUCTURE AND ELEMENTS OF COMPUTER PROGRAMS - THAT TREATS COMPUTATION AS THE EVALUATION OF MATHEMATICAL FUNCTIONS AND AVOIDS CHANGING - STATE AND MUTABLE DATA. IN COMPUTER SCIENCE, FP IS A PROGRAMMING PARADIGM - A STYLE OF BUILDING THE STRUCTURE AND ELEMENTS OF COMPUTER PROGRAMS - THAT TREATS COMPUTATION AS THE EVALUATION OF MATHEMATICAL FUNCTIONS AND AVOIDS CHANGING - STATE AND MUTABLE DATA. Someone on Wikipedia
- 3. FP HAS ITS ORIGINS IN LAMBDA CALCULUS, A FORMAL SYSTEM DEVELOPED IN THE 1930S TO INVESTIGATE COMPUTABILITY, THE ENTSCHEIDUNGSPROBLEM, FUNCTION DEFINITION, FUNCTION APPLICATION, AND RECURSION. MANY FUNCTIONAL PROGRAMMING LANGUAGES CAN BE VIEWED AS ELABORATIONS ON THE LAMBDA CALCULUS. Someone else on Wikipedia FUNCTIONAL PROGRAMMING FP HAS ITS ORIGINS IN LAMBDA CALCULUS, A FORMAL SYSTEM DEVELOPED IN THE 1930S TO INVESTIGATE COMPUTABILITY, THE ENTSCHEIDUNGSPROBLEM, FUNCTION DEFINITION, FUNCTION APPLICATION, AND RECURSION. MANY FUNCTIONAL PROGRAMMING LANGUAGES CAN BE VIEWED AS ELABORATIONS ON THE LAMBDA CALCULUS. FP HAS ITS ORIGINS IN LAMBDA CALCULUS, A FORMAL SYSTEM DEVELOPED IN THE 1930S TO INVESTIGATE COMPUTABILITY, THE ENTSCHEIDUNGSPROBLEM, FUNCTION DEFINITION, FUNCTION APPLICATION, AND RECURSION. MANY FUNCTIONAL PROGRAMMING LANGUAGES CAN BE VIEWED AS ELABORATIONS ON THE LAMBDA CALCULUS. FP HAS ITS ORIGINS IN LAMBDA CALCULUS, A FORMAL SYSTEM DEVELOPED IN THE 1930S TO INVESTIGATE COMPUTABILITY, THE ENTSCHEIDUNGSPROBLEM, FUNCTION DEFINITION, FUNCTION APPLICATION, AND RECURSION. MANY FUNCTIONAL PROGRAMMING LANGUAGES CAN BE VIEWED AS ELABORATIONS ON THE LAMBDA CALCULUS.
- 4. FOUNDATIONS FP IS BASED ON CATEGORY THEORY WHICH IS REALLY COMPLEX
- 8. FOUNDATIONS FP IS AN APPROACH BASED ON FUNCTION CALLS F(X) —> Y
- 9. FOUNDATIONS FP IS AN APPROACH BASED ON FUNCTION CALLS OOP FP Single Responsability functions Open Closed Principle functions Dependecy Inversion functions Factory pattern functions … …
- 10. FOUNDATIONS F(X) = Y ▸ Write predictable functions FP IS AN APPROACH BASED ON FUNCTION CALLS ▸ Code easier to test ▸ Thread-safe codebase ▸ Features chaining
- 11. FOUNDATIONS FP IS AN APPROACH BASED ON FUNCTION CALLS FP IS AN APPROACH BASED ON PURE FUNCTION CALLS
- 12. FOUNDATIONS F(X) = Y FP IS AN APPROACH BASED ON PURE FUNCTION CALLS currentDate 20/11/2018 INPUT tellMeTheTruth(..) ? OUTPUT
- 13. FOUNDATIONS F(X) = Y FP IS AN APPROACH BASED ON PURE FUNCTION CALLS currentDate 20/11/2018 INPUT tellMeTheTruth(..) false OUTPUT current date 21/11/2018
- 14. FOUNDATIONS F(X) = Y FP IS AN APPROACH BASED ON PURE FUNCTION CALLS currentDate 20/11/2018 INPUT migrationStatus() true OUTPUT current date 19/11/2018
- 15. FOUNDATIONS F(X) = Y FP IS AN APPROACH BASED ON PURE FUNCTION CALLS NOT PURE NO SIDE EFFECTS, TESTABLE, THREAD SAFE PURE
- 16. FOUNDATIONS F(X) = Y FP IS AN APPROACH BASED ON PURE FUNCTION CALLS NOT PURE NO SIDE EFFECTS, TESTABLE, THREAD SAFE PURE
- 17. FOUNDATIONS F(X) = Y FP IS AN APPROACH BASED ON PURE FUNCTION CALLS NOT PURE NO SIDE EFFECTS, TESTABLE, THREAD SAFE PURE
- 18. FOUNDATIONS FP IS AN APPROACH BASED ON FUNCTION CALLS FP IS AN APPROACH BASED ON PURE FUNCTION CALLS FP IS AN APPROACH BASED ON COMPOSITION OF PURE FUNCTION CALLS
- 19. FOUNDATIONS FP IS AN APPROACH BASED ON COMPOSITION OF PURE FUNCTION CALLS f(2) —> 2 * 3 = 6 g(6) —> 6 * 6 = 36 G(F(A)) = B g(f(2)) ➡ f(2) = 6 ➡ g(6) = 36
- 20. FOUNDATIONS FP IS AN APPROACH BASED ON COMPOSITION OF PURE FUNCTION CALLS FUNCTIONS ARE FIRST CLASS CITIZENS HIGH ORDER FUNCTIONS SWIFT SUPPORTS FP
- 21. FOUNDATIONS FP IS AN APPROACH BASED ON COMPOSITION OF PURE FUNCTION CALLS COMPOSITION
- 22. FOUNDATIONS FP IS AN APPROACH BASED ON COMPOSITION OF PURE FUNCTION CALLS F: A —>B G: B —>C F: INT —>INT G: INT —>INT F: INT —>INT G: INT —>INT H: INT —>STR
- 23. FOUNDATIONS FP IS AN APPROACH BASED ON COMPOSITION OF PURE FUNCTION CALLS
- 24. FOUNDATIONS FP IS AN APPROACH BASED ON COMPOSITION OF PURE FUNCTION CALLS ▸ Write predictable functions ▸ Code easier to test ▸ Thread-safe codebase ▸ Features chaining
- 26. FOUNDATIONS: IMMUTABILITY ▸ Thread-safe ADVANTAGES OF IMMUTABILITY ▸ Chaining of functions
- 27. FOUNDATIONS: IMMUTABILITY OOP (IMPERATIVE) VS FP S + DATA[I] IS “ILLEGAL” IN FP 😈 PURE FUNCTIONS MUST BE STATELESS
- 28. FOUNDATIONS: IMMUTABILITY OOP (IMPERATIVE) VS FP TAIL RECURSION IS NOT OPTIMISED IN SWIFT 🙈 TAIL RECURSION SWIFT PARTIALLY SUPPORTS FP
- 29. “A monad is just a monoid in the category of endofunctors” Someone on Internet FOUNDATIONS: FUNCTORS & MONADS
- 31. FOUNDATIONS: FUNCTORS & MONADS SWIFT OPTIONAL OPTIONAL IS A “CONTEXT” THAT CAN INCLUDE A VALUE OR NOT
- 32. FOUNDATIONS: FUNCTORS & MONADS FUNCTORS ▸ SINCE OPTIONAL IS A “CONTEXT”, WE NEED A WAY TO EXTRACT THE POSSIBLE VALUE FROM IT ▸ MAP 😍
- 33. FOUNDATIONS: FUNCTORS & MONADS FUNCTORS ▸ SINCE OPTIONAL IS A “CONTEXT”, WE NEED A WAY TO EXTRACT THE POSSIBLE VALUE FROM IT ▸ MAP 😍 OPTIONAL MAP VALUE
- 34. FOUNDATIONS: FUNCTORS & MONADS FUNCTORS OPTIONAL MAP VALUE A FUNCTOR IS A TYPE THAT CONTAINS A VALUE AND PROVIDES A MAP FUNCTION AS INTERFACE FUNCTOR MAP VALUE HINT: OPTIONAL IS A FUNCTOR FP
- 35. FOUNDATIONS: FUNCTORS & MONADS FUNCTORS A FUNCTOR IS A TYPE THAT CONTAINS A VALUE AND PROVIDES A MAP FUNCTION AS INTERFACE HINT: OPTIONAL IS A FUNCTOR ▸ Identity Law ▸ Composition Law
- 36. FOUNDATIONS: FUNCTORS & MONADS MONADS A MONAD IS JUST A MONOID IN THE BLA BLA BLA … ▸ Well a monad is just a type on which we can apply flatMap (bind) FEATURES CHAINING (ON VALUES) HINT: OPTIONAL IS A MONAD &
- 37. FOUNDATIONS: FEATURES CHAINING MONADS IN PRACTICE Well a monad is just a type on which we can apply flatMap (bind)
- 39. FOUNDATIONS: FEATURES CHAINING string f1 f2 f Out Monad String bool bool bool error error error error bind return return
- 40. FOUNDATIONS: FEATURES CHAINING string f1 f2 f Out Monad bool bool bool bool error error error error bind return return FEATURES CHAINING (ON VALUES) ERROR MANAGEMENT VS