On Thu, Jan 13, 2005 at 02:13:08PM +0000, Malcolm Wallace wrote:
Also, these modules import Data.Monoid, which contains the non-H98 instance Monoid (a -> a), making it (and these) non-portable.
I'd wrap just that instance in a #ifdef _GHC_ or actually better, #ifdef NONLINEAR_INSTANCE_HEADS . I have actually written code (already ghc dependent) which counts on that instance being available. It is quite disasterous to not have 'obvious' instances declared in a common place as then each library author has to include their own version of said instance making the libraries unable to be combined without conflicting instances! to avoid this sort of problem one shouldn't declare instances unless at least one of 1. They are writing a standalone program and not a library 2. They declared the class 3. They declared the type they are making an instance holds. the gist of all this is we should make sure every 'sensible' instance for everything declared in the libraries is made for standard types to avoid encouraging this type of collision. John -- John Meacham - ⑆repetae.net⑆john⑈