Overview of the basics of Functional Programming using the Swift programming language. Presented at the Functional Programming Miniconf at Linux.conf.au 2016, in Geelong.
$ sudo apt-get install clang libicu-dev Download a binary from https://swift.org/download/#linux; extract it $ tar xzf swift--.tar.gz $ export PATH=/path/to/usr/bin:"${PATH}" This creates a usr/ directory; add it to your path: Swift is now installed! Download the pre-requisites:
$ swift Welcome to Apple Swift version 2.1.1 (swiftlang-700.1.101.15 clang-700.1.81). Type :help for assistance. 1> let text = "Don t worry if you are not computer" text: String = "Don t worry if you are not computer" 2> text.uppercaseString $R0: String = "DON T WORRY IF YOU ARE NOT COMPUTER" 3>
–John Carmack “No matter what language you work in, programming in a functional style provides benefits. You should do it whenever it is convenient, and you should think hard about the decision when it isn't convenient.”
typealias TransformFunction = Int -> Int func manipulateArray(theArray: [Int], transform: TransformFunction) -> [Int] { var result: [Int] = [] for item in theArray { result.append(transform(item)) } return result }
// Compose a function from two functions func compose(funcA: T->T, _ funcB: T->T) -> T->T { // Return a new function that calls them both return { funcB(funcA($0)) } }
// Compose a function from two functions func compose(funcA: T->T, _ funcB: T->T) -> T->T { // Return a new function that calls them both return { funcB(funcA($0)) } } // Two dumb lil functions let double = { $0 * 2 } let addOne = { $0 + 1 }
// Compose a function from two functions func compose(funcA: T->T, _ funcB: T->T) -> T->T { // Return a new function that calls them both return { funcB(funcA($0)) } } // Two dumb lil functions let double = { $0 * 2 } let addOne = { $0 + 1 } // Compose 'em! let doubleAndAddOne = compose(double, addOne)
// Compose a function from two functions func compose(funcA: T->T, _ funcB: T->T) -> T->T { // Return a new function that calls them both return { funcB(funcA($0)) } } // Two dumb lil functions let double = { $0 * 2 } let addOne = { $0 + 1 } // Compose 'em! let doubleAndAddOne = compose(double, addOne) doubleAndAddOne(5)
import struct Swiftz.List // Cycles a finite list of numbers into an infinite list. let finite : List = [1, 2, 3, 4, 5] let infiniteCycle = finite.cycle() // Lists also support the standard map, filter, and reduce operators. let l : List = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] let twoToEleven = l.map(+1) // [2, 3, 4, 5, 6, 7, 8, 9, 10, 11] let even = l.filter((==0) • (%2)) // [2, 4, 6, 8, 10] let sum = l.reduce(curry(+), initial: 0) // 55 // Plus a few more. let partialSums = l.scanl(curry(+), initial: 0) // [0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55] let firstHalf = l.take(5) // [1, 2, 3, 4, 5] let lastHalf = l.drop(5) // [6, 7, 8, 9, 10]
Learning more • Learn You a Haskell for Great Good! • Pearls of Functional Algorithm Design • Programming in Haskell (Hutton) • Apple’s Swift Book(s) • IBM Swift Resources: https://developer.ibm.com/swift/
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