Thanks for the info.

Well, according to that explanation, all modules would be non-portable since the Prelude is normally implemented using non-standard features. I think, this is solved by declaring all modules described in the Haskell 98 Report portable.

One question: Every module which imports a non-standard module has to list all of this other module's non-portability reasons in its own reasons section again, rigtht?

You're right - the definition is incomplete. Additionally, we "declare" some modules to be portable. These modules must be available under all implementations: - The Haskell 98 standard libraries (including Prelude) - Modules listed under "Approved extensions" in that document Cheers, Simon