[Hs-Generics] Re: Owning SYB

Johan Jeuring johanj at cs.uu.nl
Mon Jul 28 17:37:30 EDT 2008

Dear Claus, Simon and others,

>> [I'm spamming libraries at haskell.org too, in case anyone interested  
>> in generics is not on generics at haskell.org.]
> Given the low number of responders on generics@, it may well be easier
> to continue on libraries@, cc-ing anyone on generics@ who isn't on  
> libraries at .

I know we have been rather quiet, but please keep mailing to the  
generics list.

As a reaction to Simon's request, we have been discussing (among  
ourselves) whether or not to take over SYB support in Utrecht.

At the moment we are working on a release of a version of EMGM, and a  
new library base on type families and GADTs (about which we have  
written a TR available via http://www.cs.uu.nl/research/techreps/UU-CS-2008-019.html) 
. I think the general feeling is that it would be a good thing to also  
release/maintain SYB, but we want to talk about this a bit more, and  
right now I am in Birmingham for a conference. I'll be back in Utrecht  
on Thursday, and we can discuss it then. Hopefully we can respond  
shortly after Thursday.

Kind regards,


>> As you know, Claus has offered a somewhat-detailed proposal for  
>> changes to the SYB library (below).  But I don't think that we have  
>> an active maintainer for any of the generic-programming libraries  
>> (esp SYB) apart from Uniplate.  Then there's the related question  
>> of what generic-programming technology to promote for clients of  
>> the GHC API.
> Thanks for raising this, Simon. I've actually been holding an email  
> summarizing several issues (not just performance of default  
> traversal schemes) that I'd like to see adressed in Syb (holding  
> because the Syb authors were/are away, and because my performance  
> improvement experiments are currently stuck on a
> GHC optimization issue). I'll send that email separately now.
>> The obvious candidates are Claus himself, or Alexey Rodriguez, or  
>> Thomas Schilling; but perhaps there are others too?  Maybe no one  
>> has stepped forward because you all think that I'm on the job!  But  
>> I'm not... I'm busy with GHC itself, and would love a maintainer  
>> for SYB and associated gubbins.  I fear that otherwise we may lose  
>> the benefits of Claus's homework.
> I'm quite willing to continue pursueing the issues I've raised until  
> I can
> make concrete suggestions for improving Syb, including summing up the
> code changes I've been adding to my various messages (certainly there
> should be patches to accompany proposal tickets in the library  
> process, and I should collect all the strands of text into a single  
> document).
> I have been waiting for the original Syb authors to return from  
> their well-earned summer camps, but there should probably be a Wiki
> page somewhere specifically for discussing Syb-related issues and  
> solutions
> (meanwhile, I've started collecting links/info related to GHC Api  
> type traversals here, including the main Syb issues:
> http://hackage.haskell.org/trac/ghc/wiki/GhcApiAstTraversals , please
> feel free to copy stuff from there to a Syb-specific page).
> But I wouldn't want to take on ownership of Syb at this point, for  
> two reasons, both motivational: (a) it helps to have someone else to  
> "blame" when the consequences of gfoldl's type once again hurt my  
> brain;-),
> (b) it is really frustrating to get so little interest in these  
> issues, well, we haven't even managed to start a proper discussion  
> on any of the lists
> I've tried, and as long as there is a Syb owner other than myself,  
> at least I won't be talking entirely to myself!-)
> Claus
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