The Towers of Hanoi – Haskell/Swift comparison

haskell_towers.hs

type Peg = String
type Move = (Peg, Peg)

hanoi :: Integer -> Peg -> Peg -> Peg -> [Move]
hanoi 0 _ _ _ = []
hanoi n a b c = hanoi (n-1) a c b ++ [(a,b)] ++ hanoi (n-1) c b a

{-
Usage:
hanoi 3 "a" "b" "c"

Result:
[("a","b"),("a","c"),("b","c"),("a","b"),("c","a"),("c","b"),("a","b")]
-}

swift_towers.swift

typealias Peg = String
typealias Move = (Peg, Peg)

func hanoi(n:Int, a:Peg, b:Peg, c:Peg) -> [Move] {
    switch n {
    case 0 : return []
    default : return hanoi(n-1, a, c, b) + [(a,b)] + hanoi(n-1, c, b, a)
    }
}

/*
Usage:
hanoi(3, "a", "b", "c")

Result:
[("a","b"),("a","c"),("b","c"),("a","b"),("c","a"),("c","b"),("a","b")]
*/

Details about the puzzle can be found here: http://en.wikipedia.org/wiki/Tower_of_Hanoi