// Learn more about F# at http://fsharp.org
// See the 'F# Tutorial' project for more help.

let rec sum'' xs =
    match xs with
    | []     -> 0
    | hd::tl -> hd + sum'' tl

let sum' xs =
    let rec loop xs' acc =
        match xs' with
        | []     -> acc
        | hd::tl -> loop tl (hd+acc)
    match xs with
    | []     -> 0
    | hd::tl -> loop tl hd

[<EntryPoint>]
let main argv =
    printfn "%A" argv
    0 // return an integer exit code