[xmonad] Strange workspace switching bug in my config

[Norbert Zeh]

wagnerdm at seas.upenn.edu [2012.05.14 2219 -0400]:
> Quoting Leo Alekseyev <dnquark at gmail.com>:
> 
> >On Sun, May 13, 2012 at 8:45 AM, Norbert Zeh <nzeh at cs.dal.ca> wrote:
> >>>myWorkspaces = ["1:terminals", "2:emacs", "3:web", "4", "5", "6",
> >>>"7","8","9","0"] ++ map (\x -> show x ++ "SCR") ([1..9]++[0])
> >>>.....
> >>>
> >>>zeroSub 0 = 10
> >>>zeroSub x = x
> >>>
> >>>jumpToMain = gets windowset >>= \W.StackSet { W.current = W.Screen {
> >>>W.workspace = w } } -> withNthWorkspace W.greedyView (-1+(zeroSub $
> >>>read [head(W.tag w)]))
> >>>jumpToScratch = gets windowset >>= \W.StackSet { W.current = W.Screen
> >>>{ W.workspace = w } } -> withNthWorkspace W.greedyView (9+(zeroSub $
> >>>read [head(W.tag w)]))
> >>
> >>The math here looks all wrong, and I'm surprised that it worked
> >>at all before.
> 
> The math looks fine to me, and in fact your suggestion:
> 
> >>What you want, I think, is the following:
> >>
> >>jumpToMain = gets (W.tag . W.workspace . W.current . windowset)
> >>        >>= W.greedyView . toMain
> >> where
> >>   toMain ws = [head ws]
> >>
> >>jumpToScratch = gets (W.tag . W.workspace . W.current . windowset)
> >>           >>= W.greedyView . toScratch
> >> where
> >>   toScratch ws | length ws == 1 = ws ++ "SCR"
> >>                | otherwise      = ws
> 
> is the one that looks dodgy to me. Notice that his main workspace
> names are things like "3:web", but the SCR-version is just "3SCR"!
> In fact, I would humbly suggest that this paragraph:

Oops.  I overlooked that the primary workspaces were not just numbered.  My bad.
I still don't get the math in the original code snippet.  zeroSub has an effect
only when its argument is 0.  So, for any starting workspace except "0" or
"0SCR", say its number is x, the above code goes to workspace x-1 or x+9.  It
should, however, go to workspace x-10 or x+10 and that conditionally on whether
the main/scratch workspace is already visible.  What is it I don't understand
here?

Cheers,
Norbert