type SortType =
    | Ascending
    | Descending
    | Unknown
    | NoSort

let rec isCurrentlySorted lastItem collectionTail currentSortType =
    match collectionTail with
    | [] -> currentSortType
    | head :: tail ->
        let suggestedSortType =
            if head = lastItem then currentSortType
            elif head > lastItem then Ascending
            else Descending
        if suggestedSortType = Unknown || suggestedSortType = currentSortType then isCurrentlySorted head tail currentSortType
        elif currentSortType = Unknown then isCurrentlySorted head tail suggestedSortType
        else NoSort

let isSorted collection =
    let currentSort = match collection with
        | [] -> NoSort
        | [single] -> Unknown
        | head :: tail -> isCurrentlySorted head tail Unknown
    match currentSort with
        | Ascending -> "Yes, ascending"
        | Descending -> "Yes, descending"
        | Unknown -> "ХЗ"
        | _ -> "No"

isSorted [1;2;3]
isSorted [3;2;1]
isSorted [3;3;3]
isSorted [1;2;2;3]
isSorted [3;2;2;1]
isSorted []
isSorted [2]
isSorted [1;2;2;2;3]
isSorted [3;2;3;1]
isSorted [3;2;2;2;0;2;-1]