Why are you not using a proper type?
Define
data Command = Cmd String (CommandHandler, (String, String))
and there will be no problem making that an instance of Eq and Ord in
the way you described.
On 19/10/06, John Goerzen
Hello,
I had this code that worked in GHC 6.4:
type CommandHandler = FTPServer -> String -> IO Bool type Command = (String, (CommandHandler, (String, String)))
instance Eq Command where x == y = (fst x) == (fst y) instance Ord Command where compare x y = compare (fst x) (fst y)
I am compiling with overlapping instances set.
In GHC 6.6, this gives an error that Eq Command is a duplicate instance of one defined in Data.Tuple. Commenting out that instance causes the Ord Command instance to fail because there is no Eq instance for CommandHandler.
After discussing it with Ian Lynagh, his conclusion was that the problem is that Data.Tuple was not compiled with overlapping instances support, and that it probably ought to be. He asked me to post here to see if everyone else felt the same way.
Thanks,
-- John _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries