[Haskell-beginners] Overlapping instances

[Brandon Allbery]

On Tue, Dec 25, 2012 at 10:52 AM, Nathan Hüsken <nathan.huesken at posteo.de>wrote:

> instance B b => A b where
>   doSomething = doMore
>

This doesn't quite do what you think; it matches *all* types, then
afterward applies the context.

Your terminology suggests you're trying to do OOP with typeclasses.  Don't;
they're not OOP, and treating them like they are leads only to grief.

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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