[Xmonad] darcs patch: make workspace tag not need to be a Num.

[Donald Bruce Stewart]

droundy:
> Hi all,
> 
> This is a change that's more pervasive than I'd originally intended.  The
> idea is to move away from the dependence on workspace tags being integers
> from 0 to size s, so that we can easily have more friendly tags, such as
> String.
> 
> This also could move us in directions of putting extra information in the
> tag.  e.g. if we stored the (Layout, [Layout]) in the tag itself, then we'd
> be able to eliminate one additional data structure, and we'd have the
> benefit that the pure StackSet code could track our layouts for us.  I'm
> not sure this is worthwhile, but the idea came to me, as I was trying to
> figure out how you'd recognize which Layout went with which Stack, and
> realized that they're tracked totally separately, which seems more than a
> little silly.
> 
> This seems particularly relevant as dons is talking about creating a Stack
> for the float layer (which makes lots of sense to me), and I'll be voting
> for allowing custom layouts to the float layer: part of my grand scheme to
> make the float layer an equal citizen with other layout systems, but also
> useful for people who want tabs on their windows so they can see titles and
> drag them around with the use of only one hand.
> 
> Anyhow, it's a sort of pervasive change--mostly in terms of the number of
> quickcheck tests that required modification because they call new--but I
> believe it's basically a simple and safe change also, and amenable to code
> review--which is why I didn't change any functionality, except that the
> tests no longer assume that workspaces are numbered 0..n-1.


Seems eminently reasonable. Though I wonder how we allow layouts to
specify, combine, or override the tag type?

How do we take advantage of a more liberal tag type, or are we not
looking that far ahead yet?

-- Don