On Fri, 2007-01-26 at 15:40 +0100, Arie Peterson wrote:
Hello,
Donald Bruce Stewart wrote:
Ok, I forgot one point. It is possible to automatically derive instances of Binary for your custom types, if they inhabit Data and Typeable, using an SYB trick. Load tools/derive/BinaryDerive.hs into ghci, and bring your type into scope, then run:
*Main> mapM_ putStrLn . lines $ derive (undefined :: Drinks)
It would seem that one needs to rerun the script every time the type is changed. That would be unfortunate. Perhaps I could have a go at writing a template haskell function to derive those instances?
I also fear that the existing script does not handle types with more than 256 constructors correctly. While uncommon, those are not unrealistic.
Feel free to send in a patch. All it needs to do is check if there are more than 2^8 constructors and if so encode the tag in a Word16 rather than Word8. Duncan