how to package Haskell libraries

[Isaac Jones <ijones@syntaxpolice.org>]

Greetings,

There has been a lot of discussion recently on the Haskell mailing
lists about the best ways to package Haskell libraries and tools for
Debian.  The main issues are:

1) there are a variety of "compiler" implementations, one of which is
an interpreter :)

2) not all Haskell implementations are available on all architectures
(ghc for instance)

3) just about every Haskell "compiler" and release is
binary-incompatible, (except maybe for nhc98).  That is, we'd need
different binaries for ghc4, ghc5, and ghc6.  Also we'd need different
binaries for profiling versions of the libraries, etc.

For instance, if I were to package HUnit, which is a simple case since
its pure Haskell code, I would need:
hunit-{hugs,nhc98} hunit-ghc{4,5,6} hunit-ghc{4,5,6}-prof

And whenever a new version of GHC6 is uploaded (for instance), all of
the packages like hunit-ghc6 would need to be updated at the same
time. That doesn't even get into the issues of the wide variety of
preprocessors that are common in this rapidly advancing language[1].
In practice, though, some packages might just be used on the newer
compilers.

This is why there aren't too many Haskell libraries in Debian right
now.  We're discussing a set of software tools that might make this
situation easier for packagers either by helping to create packages
for each version of the compiler, or by building the packages on the
user's system.

How would Debian prefer to see this?  Some people tell me that it'll
probably be too slow to build the packages on the end-user's system
(as is done for elisp), but I think it would be hard for package
maintainers to keep track of so many versions of their libraries.  I'm
leaning toward writing software tools to help package maintainers
build & maintain that large number of packages, but would this be too
many Debian packages?

peace,

isaac

[1] Haskell is designed to have a "stable" version, Haskell98, and the
compilers come with a variety of extensions so that it is very useful
as a research language as well.