On Fri, Oct 31, 2003 at 03:06:57PM -0500, Mark Carroll wrote:
Ralf Hinze and Simon Peyton-Jones wrote an interesting paper on generic programming and derivable type classes. It looked like maybe programmers would be able to write their own "deriving xml" stuff and whatever, which looked great because, if there's not already one out there, I'd love to derive some read/show analogue automatically for data in some encoding that's very efficient to write and parse (i.e. not XML (-:).
I was also wondering how the ability to write "deriving" stuff related to what one might think of as being reflection - that is, for example, could a definition of deepSeq be derived that automatically knows how to recurse into and traverse data structures and make sure everything's evaluated?
DrIFT can do this. add {-! derive: NFData !-} to your types and run the program through DrIFT then 'rnf' will reduce it to to normal form. template haskell also (among other things) lets you do your own 'deriving' clauses. Something I have been meaning to work on is having DrIFT understand the same data types as TH, so code can be shared between them much more easily... here is a list of derivables DrIFT currently supports. more are always welcome :). Binary: Binary efficient binary encoding of terms Debugging: Observable HOOD observable General: NFData provides 'rnf' to reduce to normal form (deepSeq) Typeable derive Typeable for Dynamic Generics: HFoldable Strafunski hfoldr Term Strafunski representation via Dynamic Prelude: Bounded Enum Eq Ord Read Show Representation: ATermConvertible encode terms in the ATerm format Haskell2Xml encode terms as XML Utility: has hasfoo for record types is provides isFoo for each constructor test output raw data for testing un provides unFoo for unary constructors update for label 'foo' provides 'foo_u' to update it -- --------------------------------------------------------------------------- John Meacham - California Institute of Technology, Alum. - john@foo.net ---------------------------------------------------------------------------