[Haskell-cafe] Re: Decoupling type classes (e.g. Applicative)?

[Brandon S Allbery KF8NH]

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On 11/3/10 21:30 , Maciej Piechotka wrote:
> On Tue, 2010-11-02 at 21:57 -0400, Brandon S Allbery KF8NH wrote:
>> On 10/29/10 09:35 , Dominique Devriese wrote:
>>> * Only introduce a dependency from type class A to type class B if all
>>>   functions in type class B can be implemented in terms of the
>>>   functions in type class A or if type class A is empty.
>>
>> Er?  Eq a => Ord a makes perfect sense in context but violates this law.
> 
> x == y = case x `compare` y of EQ -> True; _ -> False

So, gratuitous duplication.  Leading to the potential for the lovely case
where Eq does one thing and `compare` does something else.  This is an
improvement?

- -- 
brandon s. allbery     [linux,solaris,freebsd,perl]      allbery at kf8nh.com
system administrator  [openafs,heimdal,too many hats]  allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university      KF8NH
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