[Haskell-cafe] Re: Why Haskell?

Brian Hulley brianh at metamilk.com
Mon Jul 24 08:15:34 EDT 2006

Simon Marlow wrote:
> Neil Mitchell wrote:
>> Would it not be possible to add a GHC rule like the following:
>> forall a b . sequence a >> b  = sequence_ a >> b
>> I'm not sure if thats correct, a valid rule definition, or semantics
>> preserving, but if it was it would be nice :)
> Now there's a good idea!

Well this would work in the case of sequence vs sequence_ but it seems to me 
that what's really needed is a compiler that can do whole program 
optimization so that the list building inside sequence would be eliminated 
in this case (because the list is never used) without needing an ad-hoc 
re-write rule. Otherwise, a programmer must know about all the re-write 
rules as well as all the functions, and be able to apply them in their head 
to calculate what the space/time complexity of their program actually is, 
which imho is much more difficult than just writing sequence_ in the first 

Has anyone done work on an equivalent of MLton for Haskell?

Thanks, 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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