foldback.fsx

let foldBack folder seq state =
    let arr = Seq.toArray seq
    Array.foldBack folder arr state

let folder a b =
    let res = a + b
    //printfn "fold %A and %A giving %A" a b res
    res

let list = seq [1..1000000]

List.fold folder 0 [1..1000000]

Seq.fold folder 0 [1..1000000]

List.foldBack folder [1..1000000] 0

foldBack folder [1..1000000] 0