Serge Thanks very much for the bug report. I've fixed it, so do try again with the next release candidate.
Thanks Simon | -----Original Message----- | From: [email protected] [mailto:glasgow-haskell-bugs- | [email protected]] On Behalf Of Serge D. Mechveliani | Sent: 30 September 2010 16:34 | To: [email protected] | Cc: [email protected] | Subject: report on 7.01-pre | | Dear GHC developers, | | http://botik.ru/pub/local/Mechveliani/ghcBugs/ghc701preBug.zip | | contains a bug report on ghc-7.0.0.20100924 | tested on Debian Linux, i386-family. | | Its essence is as follows. At the fragment of | | --------------------------------------------------------------------- | instance (LinSolvRing (Pol a), CommutativeRing a) => -- (1) | LinSolvRing (UPol (Pol a)) | where | gxBasis [] = ([], []) | gxBasis fs@(f:_) = | let | UPol _ p y dP = f | (o, n) = (pPPO p, genericLength $ pVars p) | (toLex, fromLex) = (reordPol $ lexPPO n, reordPol o) | p' = toLex p | dP' = upLinSolvRing p' Map.empty | s' = cToUPol y dP' p' | ... | --------------------------------------------------------------------- | | in the module Pol3_.hs, ghc-7.0.0.20100924 reports that | the line of `s' =' needs (EuclideanRing a) and that it cannot deduce | it. | | ghc-6.12.2 compiles this in a correct way: | (EuclideanRing a) is not necessary here, while the context (1) is more | generic and sufficient. | For example, for a = DirectSum Integer Integer, | `a' has the instances (1) and has not the instance of Euclidean, and | the above code must work. | This is the idea of the author of the application; | this idea is supported by ghc-6.12.2 and not supported by | ghc-7.0.0.20100924. | | There are the two questions. | 1) Whether this intention with instances is correct in the meaning of | Haskell + ghcExt | (I hope, it is correct, at least, ghc-6.12.2 accepts it). | 2) If it is correct, why ghc-7.0.0.20100924 requires (Euclidean a) ? | | Notices | ------- | a) This application uses multiparametric classes and overlapping | instances (see docon.cabal for language and other options). | b) The example code can be reduced further, many times. | But I may have time to reduce it maybe only in the middle of | December 2010. | | Regards, | | ----------------- | Serge Mechveliani | [email protected] | _______________________________________________ | Glasgow-haskell-bugs mailing list | [email protected] | http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs _______________________________________________ Glasgow-haskell-bugs mailing list [email protected] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
