hist.fs

type HistoryBuffer () =
    let elements = ResizeArray<string>()
    let mutable current = 0

    member this.AddElement element =
        elements.Add element
        current <- elements.Count - 1

    member this.NextElement() =
        if elements.Count <> 0 then
            current <- (current + 1) % elements.Count
            elements.[current]
        else
            ""

    member this.PreviousElement() =
        if elements.Count <> 0 then
            let element = elements.[current]
            current <- if current = 0 then elements.Count - 1 else current - 1
            element
        else
            ""