instance overlap in 6.6 candidate

[Christian Maeder]

Simon Peyton-Jones schrieb:
> | instance Show [Equation]
> |   where
> |   showsPrec _ eqs =  <certain program which prints a list of equation
> |                       in a `nicer' way than by the default list

[...]

> Perhaps.  That's what I'd like feedback about.  What do others think?

Overlapping Show instances are desirable for debugging purposes or quick
and dirty code (not for "nicer" ways).

Cheers Christian