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//
// Version 3 of pagesFromData from Functional Wish Fulfillment
// http://robnapier.net/functional-wish-fulfillment
//

import Foundation

func pagesFromData(data: NSData) -> Result<[Page]> {
  return continueWith(asJSON(data)) {
    continueWith(asJSONArray($0)) {

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// Based on https://gist.github.com/kristopherjohnson/adde22d2c53adfb756a1
// Warning, this is insanely slow to compile in Beta6 (can take several minutes)
// Remove some of the |> lines to speed things up
// For more on |>, see http://undefinedvalue.com/2014/07/13/fs-pipe-forward-operator-swift

infix operator |>   { precedence 50 associativity left }

// "x |> f" is equivalent to "f(x)"
public func |> <T,U>(lhs: T, rhs: T -> U) -> U {
  return rhs(lhs)

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// Generics do not compose

// The generic f()
func f<T>(x: T) -> T { return g(x) }

// The every-day g() that f() calls
func g<T>(x: T) -> T {
  return x
}

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import Foundation

// Standard Result and Beta6-workaround Box
enum Result<A> {
  case Success(Box<A>)
  case Failure(NSError)
}

final class Box<T> {
  let unbox: T

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// Page has title and identifier propeties
// >>== is >>= (flatMap)
// Goal is to convert a Page into a future, possibly failing, list of titles of image pages
// (I'm contemplating later to defining a Promise<T> as a Future<Result<T>>)
// If there are no images, then we should return [], not an error (even though the "images" key will be missing)
// But we should return an error if parsing otherwise fails (including missing keys)
// How much information/education does an incoming dev need to be able to read this and feel
// feel comfortable doing minor adjustments to it if the API changed?

rnapier

//
// Version 1 of pagesFromData from Flat All The Things
// http://robnapier.net/flatmap
//

import Foundation

func pagesFromData(data: NSData) -> Result<[Page]> {
  return asJSON(data)
    .flatMap(asJSONArray)

rnapier

// Fun fact. You can attach associated objects onto numeric constants.
// I feel this is probably a horrible idea.

import Foundation

func ten() -> Int { return 10 }

var MyKey: Character = "0"
objc_setAssociatedObject(10, &MyKey, "I'm a value!", objc_AssociationPolicy(OBJC_ASSOCIATION_COPY))
println(objc_getAssociatedObject(10, &MyKey)) // yes

rnapier

enum Result<A> {
  case Success(Box<A>)
  case Failure(NSError)
}

// Due to current swift limitations, we have to include this Box in Result.
// Swift cannot handle an enum with multiple associated data (A, NSError) where one is of unknown size (A)
final class Box<T> {
  let unbox: T
  init(_ value: T) { self.unbox = value }

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struct Customer {
  let name: String
  let emails: [String]
}

let customers = [
  Customer(name: "Alice", emails: ["alice@example.com"]),
  Customer(name: "Bob", emails: ["bob@example.org", "bobby@home.example"])]

let names = customers.map { $0.name }

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// Claim: flatMap<Result> and continueWith are the the same function

//
// Begin with flatMap and its dependencies
//
func flatMap<T,U>(x: Result<T>, f: T -> Result<U>) -> Result<U> {
  return flatten(map(x, f))
}

func map<T, U>(x: Result<T>, f: T -> U) -> Result<U> {