On Fri, Feb 25, 2005 at 11:46:42PM +0100, Sven Panne wrote:
Apart from the recent Monoid problems, I'm a bit concerned about the non-portable ReadP creeping into some modules, making them non-H98. This affects e.g. Cabal and even something as simple as System.Info (which incorrectly claims that is portable). IMHO we should really keep at least those portable, even if this would involve a little bit more work. Is local universal quantification really needed for those simple parsing tasks? It looks a bit like overkill here...
Cabal has lots of compatibility gunk to preserve portability. It uses Distribution.Compat.ReadP, which presents a Haskell 98 interface, implemented using Text.ParserCombinators.ReadP for those that have it and re-implemented for the rest. So even though it's forcing a -98 in Hugs, it is portable, i.e. offered by every system with the same interface. Data.Version, on the other hand, has a compiler-dependent interface: #if __GLASGOW_HASKELL__ >= 603 || __HUGS__ parseVersion :: ReadP Version #elif __NHC__ parseVersion :: ReadPN r Version #else parseVersion :: ReadP r Version #endif System.Info imports that, but also presents a Haskell 98 interface.