[Haskell-cafe] The difficulty of designing a sequence class

Brian Hulley brianh at metamilk.com
Mon Jul 31 20:23:53 EDT 2006

David Menendez wrote:
> ajb at spamcop.net writes:
>> I didn't get around to fixing Sequence because there wasn't a need
>> for it yet, but yes, it should be done.
> That's a tough call to make. Changing the kind of Sequence to * from *
> -> * means losing the Functor, Monad, and MonadPlus superclasses and
> all the various maps and zips.

But there's no option if you want to be able to support non-polymorphic 
sequences like Data.ByteString etc. I think the Functor class is just 
fundamentally too limited - it assumes the whole world is polymorphic and it 

Also, MPTC's mean we would gain Monoid.

Regards, Brian.

Logic empowers us and Love gives us purpose.
Yet still phantoms restless for eras long past,
congealed in the present in unthought forms,
strive mightily unseen to destroy us.


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