readline fun

[Ian Lynagh]

Hi all,

The Debian ghc6 package curently has both a build-dependency and a
normal dependency on libreadline4-dev. The former is so the readline
library (and ghci) can be built, and the latter so compiling programs
with the readline package behaves correctly.

Now I want to move over to libreadline5-dev instead. Clearly, to build
the new ghc6, I need the old ghc6 installed, and thus need
libreadline4-dev installed (as it's a dependency). However,
libreadline4-dev and libreadline5-dev can't be installed simultaneously.

I believe this isn't a /real/ problem because the readline package of
the old GHC isn't actually needed to compile a new GHC, so
libreadline4-dev isn't actually needed. Thus I can solve this problem by
doing a build by hand on each arch. However, it would make my life a lot
easier if things weren't so entangled in the first place.

While I could just split the readline package off into a separate
ghc6-readline package for Debian, I fear this may cause confusion for
users, and it would mean satisfying cabal package deps was not
necessarily sufficient for Debian systems. So what would be really
useful for me is if the split were done by ghc itself, in much the same
way as how the opengl libraries can be split off. Then, in particular,
cabal packages using readline would have to explicit state it rather
than assuming it'll be there by default.

Does that sounds reasonable?

Of course, I still have the same problem with libgmp, but I can't see
any way around that one  :-(


Thanks
Ian