[Xmonad] heads up: xmonad zipper patch pushed

[Neil Mitchell]

Hi Dons

>     * Finally, Neil, if you want to rerun the Catch verifier on StackSet, that
>       would be neat. I think I've followed up on the changes you suggested
>       earlier in the week.

A couple of issues remain:

* You export some incomplete record selectors: "focus", "left" and "right".

* You export "with", which I thought was meant to be internal? I've
checked it even so.

* "new" and "view" both call error. To gain Catch safety you can mark
these errors as known by defining:

abort x = error x

Then calling abort, rather than error. The Safe library
[http://www-users.cs.york.ac.uk/~ndm/safe/] defines such an abort -
but its probably easier if you just define one yourself.

Everything else passes fine with Catch.

You may now use the "checked with Catch" logo on the XMonad website,
if you wish:

http://www.cs.york.ac.uk/fp/darcs/catch/extra/catch.png

Thanks

Neil