[Haskell-cafe] Simple type-class experiment turns out not so simple...

Steve Horne sh006d3592 at blueyonder.co.uk
Mon Jan 9 09:43:16 CET 2012

On 08/01/2012 20:25, Brent Yorgey wrote:
> On Fri, Jan 06, 2012 at 10:51:58AM +0000, Steve Horne wrote:
>> If I specify both extensions (-XMultiParamTypeClasses and
>> -XFlexibleInstances) it seems to work, but needing two language
>> extensions is a pretty strong hint that I'm doing it the wrong way.
> Not necessarily.  These two extensions in particular (and especially
> the second) are quite uncontroversial.
As it turns out, I don't need extensions at all, at least for 
walkableBinTree. Two answers pointed out how to handle that. I'm not yet 
entirely sure what will happen when I start adding more typeclasses 
(searchableBinTree etc) to the family - I've been distracted.

Also - after reading those answers and trying the suggestions, I'm 
pretty sure I've done tutorials that covered this after all. I must have 
just left it too long before trying them out properly.

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