Experimental package to explore functional programming in Swift.

Inspired by PointFree, objc.io and other bright minds out there.

Generic operator, which forwards a value in the next function call.

Example:

func increment(_ value: Int) -> Int { value + 1 }
func square(_ value: Int) -> Int { value * value }
2 |> increment |> square // (2 + 1) ^ 2 (result is 9)

Generic operator, which takes two functions ((A) -> B and (B) -> C) and composes them into new function (A) -> C.

Example:

func increment(_ value: Int) -> Int { value + 1 }
func isEven(_ value: Int) -> Bool { value % 2 == .zero }
func isIncrementedValueEven(_ value: Int) -> (Int) -> Bool { increment >>> isEven }
1 |> isIncrementedValueEven // (1 + 1) % 2 == 0 (result is true)

More constrained version of the Forward Composition operator, which takes two functions of the same type (A) -> A and composes them into new function of the same signature.

Example:

func increment(_ value: Int) -> Int { value + 1 }
func square(_ value: Int) -> Int { value * value }
func incrementAndSquare(_ value: Int) -> (Int) -> Int { increment <> square }
3 |> incrementAndSquare // (3 + 1) ^ 2 (result is 16)

curry is a higher-order function, that takes a function with several arguments and transforms it into a chain of single-argument functions.

NOTE: Current implementation of curry supports exactly two arguments, but overloads to handle more might be added later (if needed).

flip is a higher-order function, that takes a chain consisting of several single-argument functions and transforms it into a chain of same-signature functions, but with flipped order (except for the final result). It is often used in conjuction with curry to create more general functions and avoid code repetition at the caller site.

NOTE: Overloads to handle curried functions with more arguments might be added later (if needed).

Example:

let stringConstructor = flip(curry(String.init(data:encoding:)))
let utf8StringConstructor = stringConstructor(.utf8)
let data = … // some string data
let string = utf8StringConstructor(data) // optional string

These are just simple composable implementations of their vanilla counterparts.

Example:

func increment(_ value: Int) -> Int { value + 1 }
func square(_ value: Int) -> Int { value * value }
func isEven(_ value: Int) -> Bool { value % 2 == .zero }
[1, 2, 3, 4] |> filter(isEven) >>> map(increment >>> square) // [9, 25]