Functional Swift

Presented at NSCoder Night Copenhagen

Transcript

1. Hi! I’m ULRIK @ULRIKDAMM
2. FUNCTIONAL Swift
3. FUNCTIONS AS FIRST Class citizens
4. Int -> Int func sqr(i : Int) -> Int { return i * i } { i in i * i } ~
7. PROCEDURAL
8. 1 2 ff 2e ad load value to a load value to b > add a and b and store in c print value c
9. FUNCTIONAL
11. MAP & REDUCE
12. MAP
13. REDUCE
14. MAP & REDUCE 1 2 3 1 4 9 0 14 (((0 + 1) + 4) + 9) = 14 sqr sqr sqr + + + =
15. IN SWIFT
16. IN SWIFT func map<U>(transform: (T) -> U) -> [U] func reduce<U>(initial: U, combine: (U, T) -> U) -> U
17. IN SWIFT values.map(transform) values.reduce(initial, transform)
18. IN SWIFT [1, 2, 3].map { value in value + 1 } [1, 2, 3].reduce(0) { result, value in result + value }
19. CLOSURE SYNTAX
20. CLOSURE SYNTAX let closure : (Int, Int) -> Int = { value1, value2 -> Int in return value1 + value2 } [1, 2, 3].reduce(0, closure)
21. CLOSURE SYNTAX [1, 2, 3].reduce(0, { value1, value2 -> Int in return value1 + value2 })
22. CLOSURE SYNTAX [1, 2, 3].reduce(0, { value1, value2 -> Int in return value1 + value2 })
23. CLOSURE SYNTAX [1, 2, 3].reduce(0) { value1, value2 -> Int in return value1 + value2 }
24. CLOSURE SYNTAX [1, 2, 3].reduce(0) { value1, value2 -> Int in return value1 + value2 }
25. CLOSURE SYNTAX [1, 2, 3].reduce(0) { value1, value2 in return value1 + value2 }
26. CLOSURE SYNTAX [1, 2, 3].reduce(0) { value1, value2 in return value1 + value2 }
27. CLOSURE SYNTAX [1, 2, 3].reduce(0) { value1, value2 in value1 + value2 }
28. CLOSURE SYNTAX [1, 2, 3].reduce(0) { value1, value2 in value1 + value2 } // most common
29. CLOSURE SYNTAX [1, 2, 3].reduce(0) { value1, value2 in value1 + value2 }
30. CLOSURE SYNTAX [1, 2, 3].reduce(0) { $0 + $1 }
31. CLOSURE SYNTAX [1, 2, 3].reduce(0) { $0 + $1 } // short form
32. CLOSURE SYNTAX [1, 2, 3].reduce(0, +)
33. EXAMPLES
34. AVERAGE let values = [5, 8, 17] // procedural var sum = 0 for value in values { sum += value } let average = sum / values.count // functional values.reduce(0, +) / values.count
35. COUNT OCCURENCES func count_occurences(vals : [Int], of val : Int) -> Int { return vals.reduce(0) { count, this in return count + (val == this ? 1 : 0) } }
36. CONTAINS func contains(vals : [Int], find val : Int) -> Bool { return vals.reduce(false) { found, this in if found { return true } else { return val == this } } }
37. WORDBASE func createPositions(positions : (Int, Int)...) -> [Position] { return positions.map { position in return Position(x: position.0, y: position.1) } } func wordFromTiles(tiles : [Position]) -> String { return tiles.reduce("") { string, position in return string + self.characterAtPosition(position) } }
38. TYPE INFERENCE let ns = [1, 2, 3] ns.reduce(0, +) // 6 let ss = ["1", "2", "3"] ss.reduce("", +) // “123" let moves = [(0,1) => (0,2), (5, 7) => (7, 7)] moves.reduce(ChessBoard(), +)
39. FIN