base- not backwards compatible with base-

Stefan Holdermans stefan at
Wed Nov 19 09:06:04 EST 2008

Hi all,

Could anyone confirm the following claims?

* base- (shipped with GHC 6.10.1) is supposed to be backwards  
compatible with base- (shipped with GHC 6.8.3) ...

* ... but it isn't! (For example, the Arrow class from Control.Arrow  
is a subclass of Category from Control.Category in base-, but  
not in base-

Do we know of any similar issues? What's the recommended workaround  
when shipping code that is to support both GHC 6.8.* and GHC 6.10.*?)



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