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PAUL HUDSON — @twostraws
ELEMENTS OF
FUNCTIONAL
PROGRAMMING
www.hackingwithswift.com
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WHAT’S THE
GOAL?
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MONADS
FUNCTORS
APPLICATIVES
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WHY
BOTHER?
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CODE IS
COMING
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MAP
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[1, 2, 3, 4]
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[2, 4, 6, 8]
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camping
parking
weekend
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le camping
le parking
le weekend
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John
Paul
George
Ringo
4
4
6
5
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var result = [Int]()
for string in strings {
result.append(string.count)
}
return result
func lengthOf(strings: [String]) -> [Int] {
}
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return strings.map { $0.count }
func lengthOf(strings: [String]) -> [Int] {
}
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return strings.map { $0.count }
func lengthOf(strings: [String]) -> [Int] {
}
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return strings.map { $0.count }
func lengthOf(strings: [String]) -> [Int] {
}
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func map(_ transform: (Element) -> T) -> [T] {
var returnValue = [T]()
for item in self {
returnValue.append(transform(item))
}
return returnValue
}
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let scores = [100, 80, 85]
let formatted = scores.map {
“Your score was \($0)”
}
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let strings = [“am”, “stram”, “gram”]
let result = strings.map {
$0.uppercased()
}
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let numbers = [4.0, 9.0, 16.0]
let result = numbers.map(sqrt)
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animate(withDuration: 5)
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FLATMAP
COMPACTMAP
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init?()
try?
as?
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let a = Int(“5”)
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a: Int? = 5
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let b = Int(“non”)
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b: Int? = nil
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let input = [“1”, “5”, “Fish”]
let numbers = input.flatMap { Int($0) }
[Int]
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[“1”, “5”, “Fish”]
[Optional(1), Optional(5), nil]
[1, 5]
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let validURLs = strings.flatMap {
URL(string: $0)
}
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let imageViews = views.flatMap {
$0 as? UIImageView
}
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let valid = users.flatMap { $0 }
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OPTIONALS
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let greet = name.map { “Hi, \($0)!” }
print(greet ?? “Unknown user”)
let name: String? = getUser(id: 97)
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let greet: String
if let name = name {
greet = "Hi, \(name)!"
} else {
greet = "Unknown user"
}
print(greet)
let name: String? = getUser(id: 97)
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let number: String? = “5”
let result = number.map { Int($0) }
Int
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let number: String? = “5”
let result = number.map { Int($0) }
Int?
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let number: String? = “5”
let result = number.map { Int($0) }
Int??
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WTF?
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let number: String? = “5”
let result = number.map { Int($0) }
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let number: String? = “5”
let result = number.flatMap { Int($0) }
Int?
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map() Optional>
flatMap() Optional
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FILTER
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FILTER
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let goodWine = wine.filter {
$0.origin == “France”
}
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let banned = players.filter {
$0.hasPrefix(“Kevin”)
}
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let numbers = [1, 2, 3, 4, 5]
let odd = numbers.filter {
$0 % 2 == 1
}
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MORE
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let firstHigh = scores.first { $0 > 85 }
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let ints = [9, 5, 3, 5]
let counts = ints.map { ($0, 1) }
// [(9, 1), (5, 1), (3, 1), (5, 1)]
let dict = Dictionary(counts,
uniquingKeysWith: +)
// [9: 1, 5: 2, 3: 1]
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let numbers = Array(1…100)
let sum = numbers.reduce(0, +)
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let yes = [“oui”, “ouais”, “bien sûr”]
yes.contains(“oui”)
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let reply = “ma réponse est oui”
reply.contains(“oui”)
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let yes = [“oui”, “ouais”, “bien sûr”]
let reply = “ma réponse est oui”
yes.contains(where: reply.contains)
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CHALLENGES
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WRAP UP
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PAUL HUDSON — @twostraws
Merci beaucoup!
www.hackingwithswift.com