lemming at henning-thielemann.de
Mon Sep 29 05:57:54 EDT 2008
On Fri, 26 Sep 2008, Duncan Coutts wrote:
> On Fri, 2008-09-26 at 21:51 +0100, Simon Marlow wrote:
>> There are basically only two sensible choices for the Functor instance
>> for (->):
>> (a) don't define one at all
>> (b) define one in Control.Monad, and give up on Haskell 98 compliance
>> The current situation, namely
>> (c) define it as an orphan, and give up on module abstraction
>> is not a sensible choice.
> No orphan instances in libraries.
Me too. Although I'm afraid some of my packages still contain orphan
instances. When I need a new instance to an existing class+type I ask the
library author for that instance and in the meantime I use a 'newtype'.
Frequently a newtype turns out to be better anyway.
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