showUnique

[George Russell]

I support the suggestion of providing
   instance Show Unique
I would also support having
   instance Read Unique

As John says, the representation of a Unique value as a String should be
completely undefined except that
   u == u' iff showUnique u == showUnique u'

In UniForM we have a similar type to Unique which also instances
   (Eq,Ord,Show,Read)
One advantage of instancing Show is that it makes it easier to debug programs
which use Unique values.  Read is more debatable, but I'm sure we use it somewhere.