[Hs-Generics] Re: Owning SYB

José Pedro Magalhães jpm at cs.uu.nl
Fri Aug 1 02:36:37 EDT 2008

Hello all,

As Johan mentioned, here in Utrecht we are working on libraries for generic
programming. We want to make it easier for people to use generic libraries,
so we are packaging EMGM [1] and a library for generic programming for
mutually recursive datatypes [2]. We intend to release these on Hackage soon
(Summer vacations are delaying us a bit), along with useful generic
applications (a zipper and a generic rewriting framework).
Maintaining SYB fits well in this idea, and if no other natural maintainers
volunteer, I (with some support from the other people at Utrecht) am happy
to take it upon me. I probably won't do heavy development on the library,
but including patches, and providing support is fine. We're also planning to
maintain EMGM here in Utrecht, although we didn't develop that ourselves.

Recently, (at least) Claus and Oleg have been posting interesting
suggestions of improvements/modifications to SYB. Those should be further
analyzed and discussed, and finally introduced (or not) in the library. The
generic map for SYB, for instance, evolved from the "impossible to
implement", through the "unsafe implementation", until the latest gmap2 as
described by Oleg [3]. If further tests show this function behaves as
expected, then it's clearly a good candidate for extending SYB. We should
also rethink if other things previously deemed impossible remain so.

Maintaining SYB, alongside with the other generic libraries, will require
things such as:
 * Releasing packages in Hackage, properly documented with Haddock;
 * Updating such packages as necessary for new releases of GHC;
 * Writing examples of how to use the libraries (from a user perspective);
 * Writing testsuites, which are important for checking backwards
compatibility of any changes;
 * Having an updated webpage linking to the library sources, documentation,
possibly a bug tracker, etc.
These are all things we plan to do for the libraries.

Additionally, we could think of improving syb-with-class [4] in parallel
with regular SYB. This is something to ask to its maintainer.


[2] http://www.cs.uu.nl/research/techreps/UU-CS-2008-019.html
[3] http://www.haskell.org/pipermail/generics/2008-July/000362.html
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