This crash is fixed, in the HEAD and 6.4. It turned out to be a desugaring bug involving existentials etc. Simon | -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users- | bounces@haskell.org] On Behalf Of Akos Korosmezey | Sent: 18 February 2005 20:05 | To: GHC-users list | Subject: gunfoldl | | | I wrote a little data structure with quantified constructors: | | module MyModule where | import Data.Generics | import Data.HashTable | | data Item = forall a. (Data a) => Leaf Bool a | | forall a. (Data a) => Branch Bool a Int Int | | deriving (Typeable) | | I want it to make an instance of Data: | | instance Data Item where | gfoldl k z (Leaf b v) = z (Leaf b) `k` v | gfoldl k z (Branch b v a1 a2) = z (\x -> Branch b x a1 a2) `k` v | --gunfoldl k z c = case constrIndex c of | -- 1 -> k z (Leaf undefined | undefined) | toConstr (Leaf _ _) = leafConstr | toConstr (Branch _ _ _ _) = branchConstr | dataTypeOf _ = itemDataType | | itemDataType = mkDataType "Subliminal.Item" [leafConstr, branchConstr] | leafConstr = mkConstr itemDataType "Leaf" [] Prefix | branchConstr = mkConstr itemDataType "Branch" [] Prefix | | But, when I try to compile it with ghc-6.4-20050217: | | ghc -fglasgow-exts -i. -c kicsi.hs | | kicsi.hs:13:4: | Warning: No explicit method nor default method for `gunfold' | In the instance declaration for `Data Item' | ghc-6.4.20050217: panic! (the `impossible' happened, GHC version | 6.4.20050217): | cgPanic | k{v a1vu} | static binds for: | local binds for: | gunfold{v r22q} | SRT labelghc-6.4.20050217: panic! (the `impossible' happened, GHC | version 6.4.20050217): | initC: srt | | Please report it as a compiler bug to glasgow-haskell-bugs@haskell.org, | or http://sourceforge.net/projects/ghc/. | | If I uncomment the gunfoldl lines: | | ghc -fglasgow-exts -i. -c kicsi.hs | | kicsi.hs:12:8: `gunfoldl' is not a (visible) method of class `Data' | | Compilation exited abnormally with code 1 at Fri Feb 18 20:55:32 | | Could you please help me? | | Thanks | Akos | -- | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | ~~~~~~ | Akos Korosmezey Tel: +36-1-439-5936 | Ericsson Telecom Ltd. ETH/GSCD/RUNB Fax: +36-1-437-7576 | P.O.B. 107, H-1300 Budapest, Hungary Home: +36-26-342-687 | mailto:Akos.Korosmezey@ericsson.com Mobile: +36-30-740-7732 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | ~~~~~~ | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users