Haskel Fmap in Swift. Get optiona value and call function with that values as parameter

fmap.swift

infix operator <^> { associativity left }

func <^><A, B>(f: A -> B, a: A?) -> B? {
  
  switch a {
  case .Some(let x): return f(x)
  case .None: return .None
  }
}

fmapExample.swift

func increment(someNumber: Int) -> Int {
  return someNumber + 1
}

increment <^> 5   // Some 6
increment <^> nil


let s = { $0 + 1 } <^> 10
let s0 = { a in a + 1 } <^> nil