Hello Malcolm, Thursday, November 2, 2006, 12:46:43 AM, you wrote:
instance Num (Bar z) where and instance Num (Bar z)
The former declares that _no_ methods are defined (except for defaults), and the latter, with your proposal, that _all_ methods are defined. The
i join to this note. moreover, currently GHC supports "generics for the masses" that may mean very subtle semantic changes between code generated by these two forms :)) i think it will be better to use derive/deriving/derived prepended to the former: derive instance Num (Bar z) derive instance Num z => Num (Bar z) and allow generics/TH/other forms of user-specified deriving to catch such declarations and provide alternative to compiler-wired deriving mechanism. so we can imagine that we discuss some general deriving syntax that in future will be reused by new Haskell extensions -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com