overlapping instances and constraints
bulat.ziganshin at gmail.com
Wed Mar 1 11:30:35 EST 2006
Wednesday, March 1, 2006, 6:23:00 PM, you wrote:
>> instance (Show a) => IsXML a where
>> toXML = toXML . show
>> The intention of the latter is to be a default instance unless another
>> instance is specified.
BRG> I can see how this is useful, but I'm surprised that it's robust. None of
BRG> the extensions people have suggested to avoid overlap would help here, clearly.
precedence 1 : instance (Show a) => IsXML a where ...
precedence 9 : instance IsXML String where ...
of overlapping instances, win the one with higher precedence
Bulat mailto:Bulat.Ziganshin at gmail.com
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