21. E D
func valueChanger<T, U>(value: T, _ f: (T) -> U) -> U {
return f(value)
}
let name = "Original"
// Original
let changedName = valueChanger(value: name) { "($0) Changed" }
// Original Changed
22. E D
class Functor<T> {
let value: T
init(_ v: T) {
value = v
}
func map<U>(_ f: (T) -> U) -> Functor<U> {
let u = f(value)
return Functor<U>(u)
}
}
23. E D
let name = "Original" // Original
let changedName = Functor(name).map { "($0) Changed" }.value
// Original Changed
let changedNameLength = Functor(name) // Functor<String>
.map { "($0) Changed" } // Functor<String>
.map { $0.count } // Functor<Int>
.map { $0 * $0 } // Functor<Int>
.value // Int
// 256
24. E D
func stringLength(_ s: String) -> Functor<Int> {
return Functor(s).map { $0.count }
}
let name = "Original" // Original
let changedName = Functor(name).map { "($0) Changed" }.value
// Original Changed
let changedNameLength = Functor(name) // Functor<String>
.map { "($0) Changed" } // Functor<String>
.map (stringLength) // Functor<Functor<Int>>
.map { $0 * $0 }
.value
25. E D
func stringLength(_ s: String) -> Functor<Int> {
return Functor(s).map { $0.count }
}
let name = "Original" // Original
let changedName = Functor(name).map { "($0) Changed" }.value
// Original Changed
let changedNameLength = Functor(name) // Functor<String>
.map { "($0) Changed" } // Functor<String>
.map (stringLength) // Functor<Functor<Int>>
.map { $0 * $0 }
.value
Functor<Functor<Int>> 의 중첩된 것을 단일(Mono)하게 만들어야 함.
26. class Monad<T>: Functor<T> {
override func map<U>(_ f: (T) -> U) -> Monad<U> {
let cu = super.map(f)
return Monad<U>(cu.value)
}
func flatMap<U>(_ f: (T) -> Functor<U>) -> Monad<U> {
let fu = f(value)
return Monad<U>(fu.value)
}
}
27. func stringLength(_ s: String) -> Functor<Int> {
return Functor(s).map { $0.count }
}
let name = "Original" // Original
let changedName = Monad(name).map { "($0) Changed" }.value
// Original Changed
let changedNameLength = Monad(name) // Monad<String>
.map { "($0) Changed" } // Monad<String>
.flatMap (stringLength) // Monad<Int>
.map { $0 * $0 } // Monad<Int>
.value // Int
//256
28. E I
Immutable data 는 변하지 않는 값
f
g = f - ) -
b df - )
-) ).-
e f P
map / flatMap
Data
get / set
유지보수하기 좋다