[xmonad] how do I get a layout like this?

[Karl Hasselström]

[ Apologies if this is a duplicate -- I haven't seen it show up on the
  list, so I'm resending from the address that I subscribed with. ]

Hi all.

I just started using xmonad, and there's a layout I want to have but
can't quite figure out how to get. I'm sure it's just a matter of
gluing the right pieces from the contrib library together, but I
haven't gotten it right yet.

I want the workspace to be divided vertically into two areas. Each
area should show just one window at a time. Pressing Alt-Tab (or
something) should cycle through, in the currently focused half of the
screen, all windows except the one that's visible in the other area.
The idea being that visible but non-focused windows should stay
visible and non-focused.

For example, assume the workspace has five windows, A through E, with
C and E currently visible. Alt-Tabbing when the focus is on the left
half of the workspace should cycle through A, B, C, and D; if the
right half is focused, we should cycle through A, B, D, and E.

XMonad.Actions.CycleWS lets me do exactly this with workspaces and two
Xinerama screens, by binding (moveTo Next HiddenNonEmptyWS) to a key.

-- 
Karl Hasselström, kha at treskal.com
      www.treskal.com/kalle