[Haskell-cafe] seq (was: Article review: Category Theory)

Lennart Augustsson lennart at augustsson.net
Fri Jan 19 22:47:42 EST 2007

This solution was used in the first place.  But then some people were  
too lazy
to actually use the Eval (as Seq was called) class, so they wanted
a polymorphic seq.  And so we're in this mess.  And it is a mess,
e.g., the foldr/build transformation ghc uses to fuse list processing
isn't really valid when you have seq.

	-- Lennart

On Jan 19, 2007, at 18:09 , Brian Hulley wrote:

> Neil Mitchell wrote:
>> Hi Brian,
>>> Is there any solution that would allow excess laziness to be removed
>>> from a Haskell program such that Hask would be a category?
>> class Seq a where
>>    seq :: a -> b -> b
>> Then you have a different seq based on the types, and it doesn't go
>> wrong. You would probably want deriving Seq support.
> This seems an amazingly neat solution to a really terrible problem,  
> so:
> 1) Does anyone know why this was not used in the first place?
> 2) Would it be good to use this in future versions of Haskell?
> 3) Is there any practical program which requires the current seq  
> that could not be rewritten to use the typeclass seq?
> Thanks, Brian.
> -- 
> http://www.metamilk.com
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