TH maestros This bug turns out to be simply that Template Haskell is only set up for Haskell 98, whereas Jon Cast wants to manipulate multi-parameter type clases. Should we add multi-param type classes to THSyntax? Does anyone feel like doing it? It's a fairly routine matter, but it does mean changing the data type. (Another reason to use bracket syntax!) Simon | -----Original Message----- | From: glasgow-haskell-bugs-bounces@haskell.org [mailto:glasgow-haskell-bugs- | bounces@haskell.org] On Behalf Of SourceForge.net | Sent: 09 October 2003 18:51 | To: noreply@sourceforge.net | Subject: [ ghc-Bugs-820778 ] Malformed Predicate w/ Template Haskell | | Bugs item #820778, was opened at 2003-10-09 12:51 | Message generated for change (Tracker Item Submitted) made by Item Submitter | You can respond by visiting: | https://sourceforge.net/tracker/?func=detail&atid=108032&aid=820778&grou p_id=8032 | | Category: Compiler (Type checker) | Group: 6.0.1 | Status: Open | Resolution: None | Priority: 5 | Submitted By: Jon Cast (jcast) | Assigned to: Nobody/Anonymous (nobody) | Summary: Malformed Predicate w/ Template Haskell | | Initial Comment: | The following two modules: | | --- Cut --- | | module ScratchTemplates where | | import Language.Haskell.THSyntax | | newtype Interaction a = Interaction a deriving Show | | ret = Interaction | | instance Monad Interaction where | return = Interaction | Interaction x >>= f = f x | | instance Functor Interaction where | fmap f x = x >>= return . f | | interactionT t = tcon (TconName "Interaction") `tapp` t | | class Flatten a b | a -> b where | flatten :: a -> b | | flattenT :: TypQ -> TypQ -> TypQ | flattenT t t' = tvar "Flatten" `tapp` t `tapp` t | | baseType t = sequence [ | inst (return []) (flattenT t t) | [val (pvar "flatten") (normal (var "id")) []], | inst (return []) (flattenT (interactionT t) | (interactionT t)) | [val (pvar "flatten") (normal (var "id")) []]] | | instance Flatten a b => | Flatten (Interaction (Interaction a)) | (Interaction b) where | flatten a = a >>= id >>= return . flatten | | module Main where | | import Monad | import ScratchTemplates | import Language.Haskell.THSyntax | | $(baseType (tcon (Tuple 0))) | | instance Flatten String String where | flatten a = a | | instance Flatten (Interaction String) (Interaction | String) where | flatten a = a | | instance Flatten b c => Combine String b (String, c) where | combine a b = liftM2 (,) a (fmap flatten b) | | instance Flatten Int Int where | flatten a = a | | class Combine a b c | a b -> c where | combine :: Interaction a -> Interaction b -> | Interaction c | | instance Combine () b b where | combine a b = b | | instance Flatten b c => Combine Int b (Int, c) where | combine a b = do | x <- a | y <- fmap flatten b | return (x, y) | | instance (Flatten b c, Combine a c d) => | Flatten (Interaction a, Interaction b) | (Interaction d) where | flatten (a, b) = combine a (fmap flatten b) | | main = main | | --- Cut here --- | | loaded into ghci -fglasgow-exts produce the following | error message: | | Compiling ScratchTemplates ( ScratchTemplates.hs, | interpreted ) | Compiling Main ( scratch.hs, interpreted ) | ghc-6.0.1: panic! (the `impossible' happened, GHC | version 6.0.1): | Malformed predicate | | Please report it as a compiler bug to | glasgow-haskell-bugs@haskell.org, | or http://sourceforge.net/projects/ghc/. | | | ---------------------------------------------------------------------- | | You can respond by visiting: | https://sourceforge.net/tracker/?func=detail&atid=108032&aid=820778&grou p_id=8032 | _______________________________________________ | Glasgow-haskell-bugs mailing list | Glasgow-haskell-bugs@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs