Btw, I also have problems with the haskell-src-exts that imports Data.Generics.Instances (to generate Data and Typeable instances). Where would these have moved to in the new base?
ghc-pkg provides general help for finding packages for modules: $ ghc-pkg find-module Data.Generics.Instances c:/ghc/ghc-6.11.20081004\package.conf: base-3.0.3.0, syb-0.1.0.0 So there is a compatibility module in the new syb. Unfortunately, that won't tell you about the moves and rationale. Most of the time, you'll want Data.Data (check "ghc -e ':browse Data.Data'" or the Haddock pages, or google for "syb" in the libraries@ archives): $ ghc-pkg find-module Data.Data c:/ghc/ghc-6.11.20081004\package.conf: base-4.0.0.0 $ ghc -ignore-dot-ghci -e ':browse Data.Data' | grep class class (Typeable a) => Data a where class Typeable a where typeOf :: a -> TypeRep class Typeable1 t where typeOf1 :: t a -> TypeRep class Typeable2 t where typeOf2 :: t a b -> TypeRep class Typeable3 t where typeOf3 :: t a b c -> TypeRep class Typeable4 t where typeOf4 :: t a b c d -> TypeRep class Typeable5 t where typeOf5 :: t a b c d e -> TypeRep class Typeable6 t where typeOf6 :: t a b c d e f -> TypeRep class Typeable7 t where typeOf7 :: t a b c d e f g -> TypeRep $ ghc -ignore-dot-ghci -e ':info Data.Data.Data' class .. instance ..
.. I would prefer to use the new base-4 when possible. The cabal file already includes a conditional "if flag(splitBase)" to handle really old versions, I guess what I'm asking for is something similar for this case. Is there a splitSyb flag or some such?
I was wondering whether there is a way to set user-defined flags depending on whether some package is available. Then I recalled that flags don't work the way I expected - instead Cabal will try all flag settings to find a buildable configuration (a fact I only became aware of when a different kind of flag was added recently that does behave the way I expected;-). Which might be what you want in this case. Duncan: is this correct, and are these subtleties documented somewhere?
Though obviously this would only work if the module Data.Generics.Instances was preserved under that name somewhere else. If it was renamed or changed (which I suspect), then the hassle of keeping up to date with older versions will probably be too much, and I will want to update to the new agenda as soon as 6.10 is released for real. So what happened to this module? (Is there a migration quicksheet somewhere?)
Pedro: it might be helpful if the haddock pages for the old and new syb modules were to point to a syb wiki page (which could then link to the relevant threads on libraries@)? Or is that information already in the documentation patch for the latest builds? Claus