Functional programming in Swift
Swift Other
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Swiftz

Swiftz is a Swift library for functional programming.

It defines functional data structures, functions, idioms, and extensions that augment the Swift standard library.

For a small, simpler way to introduce functional primitives into any codebase, see Swiftx.

Introduction

Swiftz draws inspiration from a number of functional libraries and languages. Chief among them are Scalaz, Prelude/Base, SML Basis, and the OCaml Standard Library. Elements of the library rely on their combinatorial semantics to allow declarative ideas to be expressed more clearly in Swift.

Swiftz is a proper superset of Swiftx that implements higher-level data types like Arrows, Lists, HLists, and a number of typeclasses integral to programming with the maximum amount of support from the type system.

To illustrate use of these abstractions, take these few examples:

Lists

import struct Swiftz.List

//: Cycles a finite list of numbers into an infinite list.
let finite : List<UInt> = [1, 2, 3, 4, 5]
let infiniteCycle = finite.cycle()

//: Lists also support the standard map, filter, and reduce operators.
let l : List<Int> = [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]

Semigroups and Monoids

let xs = [1, 2, 0, 3, 4]

import protocol Swiftz.Semigroup
import func Swiftz.sconcat
import struct Swiftz.Min

//: The least element of a list can be had with the Min Semigroup.
let smallestElement = sconcat(Min(2), t: xs.map { Min($0) }).value() // 0

import protocol Swiftz.Monoid
import func Swiftz.mconcat
import struct Swiftz.Sum

//: Or the sum of a list with the Sum Monoid.
let sum = mconcat(xs.map { Sum($0) }).value() // 10

import struct Swiftz.Product

//: Or the product of a list with the Product Monoid.
let product = mconcat(xs.map { Product($0) }).value() // 0

Arrows

import struct Swiftz.Function
import struct Swiftz.Either

//: An Arrow is a function just like any other.  Only this time around we
//: can treat them like a full algebraic structure and introduce a number
//: of operators to augment them.
let comp = Function.arr(+3)  Function.arr(*6)  Function.arr(/2)
let both = comp.apply(10) // 33

//: An Arrow that runs both operations on its input and combines both
//: results into a tuple.
let add5AndMultiply2 = Function.arr(+5) &&& Function.arr(*2)
let both = add5AndMultiply2.apply(10) // (15, 20)

//: Produces an Arrow that chooses a particular function to apply
//: when presented with the side of an Either.
let divideLeftMultiplyRight = Function.arr(/2) ||| Function.arr(*2)
let left = divideLeftMultiplyRight.apply(.Left(4)) // 2
let right = divideLeftMultiplyRight.apply(.Right(7)) // 14

Operators

See Operators for a list of supported operators.

Setup

To add Swiftz to your application:

Using Carthage

  • Add Swiftz to your Cartfile
  • Run carthage update
  • Drag the relevant copy of Swiftz into your project.
  • Expand the Link Binary With Libraries phase
  • Click the + and add Swiftz
  • Click the + at the top left corner to add a Copy Files build phase
  • Set the directory to Frameworks
  • Click the + and add Swiftz

Using Git Submodules

  • Clone Swiftz as a submodule into the directory of your choice
  • Run git submodule init -i --recursive
  • Drag Swiftz.xcodeproj or Swiftz-iOS.xcodeproj into your project tree as a subproject
  • Under your project's Build Phases, expand Target Dependencies
  • Click the + and add Swiftz
  • Expand the Link Binary With Libraries phase
  • Click the + and add Swiftz
  • Click the + at the top left corner to add a Copy Files build phase
  • Set the directory to Frameworks
  • Click the + and add Swiftz

Using Swift Package Manager

  • Add Swiftz to your Package.swift file's dependencies section:
.Package(url: "https://github.com/typelift/Swiftz", versions: Version(0,6,0)..<Version(1,0,0))

System Requirements

Swiftz supports OS X 10.9+ and iOS 8.0+.

License

Swiftz is released under the BSD license.