    -----------------------------------------------------------------------------
    -- |
    -- Module       : XMonad.Actions.RotSlaves
    -- Copyright    : (c) Hans Philipp Annen <haphi@gmx.net>, Mischa Dieterle <der_m@freenet.de>
    -- License      : BSD3-style (see LICENSE)
    --
    -- Maintainer   : Hans Philipp Annen <haphi@gmx.net>
    -- Stability    : stable
    -- Portability  : unportable
    --
    -- Rotate all windows except the master window and keep the focus in
    -- place.
    -----------------------------------------------------------------------------
    module XMonad.Actions.RotSlaves (
            -- $usage
            rotSlaves', rotSlavesUp, rotSlavesDown,
            rotAll', rotAllUp, rotAllDown
            ) where

    import XMonad.StackSet
    import XMonad

    -- $usage
    --
    -- To use this module, import it with:
    --
    -- > import XMonad.Actions.RotSlaves
    --
    -- and add whatever keybindings you would like, for example:
    --
    -- > , ((modm .|. shiftMask, xK_Tab   ), rotSlavesUp)
    --
    -- This operation will rotate all windows except the master window,
    -- while the focus stays where it is. It is useful together with the
    -- TwoPane layout (see "XMonad.Layout.TwoPane").
    --
    -- For detailed instructions on editing your key bindings, see
    -- "XMonad.Doc.Extending#Editing_key_bindings".

    -- | Rotate the windows in the current stack, excluding the first one
    --   (master).
    rotSlavesUp,rotSlavesDown :: X ()
    rotSlavesUp   = windows $ modify' (rotSlaves' (\l -> (tail l)++[head l]))
    rotSlavesDown = windows $ modify' (rotSlaves' (\l -> [last l]++(init l)))

    -- | The actual rotation, as a pure function on the window stack.
    rotSlaves' :: ([a] -> [a]) -> Stack a -> Stack a
    rotSlaves' _ s@(Stack _ [] []) = s
    rotSlaves' f   (Stack t [] rs) = Stack t [] (f rs)                -- Master has focus
    rotSlaves' f s@(Stack _ ls _ ) = Stack t' (reverse revls') rs'    -- otherwise
        where  (master:ws)     = integrate s
               (revls',t':rs') = splitAt (length ls) (master:(f ws))

    -- | Rotate all the windows in the current stack.
    rotAllUp,rotAllDown :: X ()
    rotAllUp   = windows $ modify' (rotAll' (\l -> (tail l)++[head l]))
    rotAllDown = windows $ modify' (rotAll' (\l -> [last l]++(init l)))

    -- | The actual rotation, as a pure function on the window stack.
    rotAll' :: ([a] -> [a]) -> Stack a -> Stack a
    rotAll' f s = Stack r (reverse revls) rs
        where (revls,r:rs) = splitAt (length (up s)) (f (integrate s))