> 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)
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