Swift folding

gistfile1.swift

operator infix |> {associativity left precedence 140}
func |> <T,U> (left: @auto_closure () -> T,right: T -> U) -> U {
    return right(left())
}

func fold<S,T>(f : (S,T) -> S,acc: S)(s : Array<T>) -> S {
    if s.isEmpty {
        return acc
    }
    else {
        return fold(f,f(acc,s[0]))(s: Array(s[1..s.count]))
    }
}


// Ints
let z =
    [1,2,3,4,5,6]
        |> fold({
        (acc,value) in
            return acc + value
        },0)

// Not generic as it relies on the + operator (Swift type hierarchy makes this difficult to make generic - will try and work out a better solution)
func sum(s : Array<Int>, seed: Int) -> Int {
        return s |> fold({(acc,value) in acc + value},seed)
    }

sum([1,2,3,4,5],10) // 25
sum([],0) // 0



// Strings
let z1 =
    ["Andy","Calderbank"]
        |> fold({
            (acc,value) in
            acc + ":" + value
},"Name") // Name:Andy:Calderbank