instance CommandFunction (Sh st ()) st where ^ I think your first argument (on which the second has a functional dependence) does not determine the second argument, since it makes use of st in the first argument. This strikes me as a likely place to begin.
Dan Robert wrote:
Fellow Haskellers,
I have a package that uses some light typeclass hackery to automaticly build parsing algorithms based on the type of a function.
I was recently informed that my package doesn't compile on GHC 6.6 due to the new restrictions on FD resolution; in particular I have instance declarations which fail the coverage condition. I can use undecidable instances to make the package compile again, but I'd prefer not to if I can avoid it. class CommandFunction f st | f -> st where parseCommand :: String -> f -> CommandParser st commandSyntax :: f -> [Doc]
instance CommandFunction (Sh st ()) st where
parseCommand wbc m str = -- list monad do (x,[]) <- runRegex (maybeSpaceBefore (Epsilon (CompleteParse m))) str return x
commandSyntax _ = []
instance CommandFunction r st => CommandFunction (Int -> r) st where parseCommand = doParseCommand Nothing intRegex id commandSyntax f = text (show intRegex) : commandSyntax (f undefined)
instance CommandFunction r st => CommandFunction (Integer -> r) st where parseCommand = doParseCommand Nothing intRegex id commandSyntax f = text (show intRegex) : commandSyntax (f undefined)