instance visibility

José Pedro Magalhães jpm at
Tue Sep 30 09:52:37 EDT 2008

I'm trying to understand the implications of this discussion in the current
splitting off of SYB from base. In the division that was more or less agreed
[1], the Data class and its uncontested instances would be kept in base,
whereas the rest would go into a new syb package. The instances were
traditionally orphans in Data.Generics.Instances, but it was suggested that
they should now be moved into Data.Generics.Basics. This would make SYB free
of orphans, but no longer offers a user the possibility of avoid the import
of Data.Generics.Instances to define its own instances. It also invalidates
some of the changes proposed in [1], namely caring about the imports of
Data.IntMap, Data.IntSet, etc.

So my question is: should Data.Generics.Instances indeed be folded into
Data.Generics.Basics (which contains the Data class and associated stuff)?
(Worth noting is that the instances that are moved to the syb package will
remain orphans, but the idea is that those might change or disappear in the


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