MaybeInt.swift

import Foundation

enum MaybeInt {
    case Nothing
    case Just(Int)
}

extension MaybeInt : Printable {
    var description : String {
        switch self {
        case .Nothing:
            return "Nothing"
        case .Just(let x):
            return "\(x)"
        }
    }
}

infix operator >>= { associativity left precedence 120 }
func >>= (left: MaybeInt, right: (Int -> MaybeInt)) -> MaybeInt {
    switch left {
    case .Nothing:
        return .Nothing
    case .Just(let x):
        return right(x)
    }
}

let result1 = MaybeInt.Just(1) >>= { x in return MaybeInt.Just(x + 1) }
println(result1) //=> "2"

let result2 = MaybeInt.Just(1) >>= { x in return MaybeInt.Just(x + 1) } >>= { _ in return MaybeInt.Nothing }
println(result2) //=> "Nothing"