Tail Recursive QuickSort using Continuation Passing Style

//val qsort: 'a list -> 'a list
let rec qsort = function
                | [] -> []
                | x::xs' -> let (l, r) = List.partition ((>) x) xs'
                            List.concat [(qsort l);[x];(qsort r)]

//val qsortCPS: 'a list -> 'a list
let qsortCPS xs =   
    let rec loop xs cont =
            match xs with
            | [] -> cont []
            | x::xs' -> let (l, r) = List.partition ((>) x) xs'                          
                        loop l (fun lacc ->
                        loop r (fun racc -> cont (lacc @ x :: racc)))
    loop xs (fun x -> x)