Hi All, Thanks to everyone for their comments. I can see that this is quite a difficult design problem, and it is unlikely that one solution will please everyone, which makes me think that the current solution will probably stand. Simon Peyton-Jones writes:

Bernie writes: | anymore. What I would like is that the defualting rules refer | to the classes in my version of the Prelude, | not the Standard Prelude.

You can always get that (with the -fno-implicit-prelude thing) by adding

default [Int, Double]

or whatever to your source module, just after the import that gets your new standard Prelude. Doesn't that do it?

I'll get back to you on this soon.

It would also not be hard to arrange that the "default default" declaration became scoped with -fno-implicit-prelude (like fromInteger), if that was useful.

That sounds a lot like what I would like to have, but I'm probably being selfish here.

It's a good point; I thought that *all* the numeric stuff was un-coupled from the Prelude with -fno-implicit-prelude, but it isn't quite.

What I would like to know is the semantics of -fno-implicit-prelude with respect to this bit from the Haskell Report: "4.3.4 Ambiguous Types, and Defaults for Overloaded Numeric Operations Ambiguities in the class Num are most common, so Haskell provides another way to resolve them---with a default declaration: default (t1 , ... , tn) where n>=0, and each ti must be a monotype for which Num ti holds. ^^^^^^^^^^ In situations where an ambiguous type is discovered, an ambiguous type variable is defaultable if at least one of its classes is a numeric class (that is, Num or a subclass of Num) and if all of its classes are defined ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ in the Prelude or a standard library ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Each defaultable variable is replaced by the first type in the default list that is an instance of all the ambiguous variable's classes. It is a static error if no such type is found." Do these become "whatever Num is in scope" when I use -fno-implicit-prelude, and "whatever classes from standard libraries" are in scope? If they don't then I think I'm in a pickle. Ooroo, Bernie.