On Thu, Feb 02, 2006 at 03:34:57PM +0300, Bulat Ziganshin wrote:
JM> Also, the need for it is questionable if we were to allow polymorphic JM> components and newtype deriving. if your data acts differently then it JM> should be a different type with a newtype and derive all the properties JM> where it acts the same. if you want to do different things to the same JM> data then packaging them up as values in a record with polymorphic JM> components makes perfect sense and is more functional in nature. That JM> class instances are global is a great feature of them, not a weakness.
John, local definitions used in Generic Haskell (which you may don't know) and even in the SYB. are you really think that if we need two different algorithms of processing Identifier inside folds, then we should define two different Identifier types?
hmm? no. that is why I said if you want to do different related things to the same data then higher order functions packaged with polymorphic components is the way to go. In any case, the gist wasn't so much don't implement something as much as please don't break the current class global scope invarients in the process. John -- John Meacham - ⑆repetae.net⑆john⑈