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: glasgow-haskell-bugs-boun...@haskell.org [mailto:glasgow-haskell-bugs-
| boun...@haskell.org] On Behalf Of Serge D. Mechveliani
| Sent: 30 September 2010 16:34
| To: glasgow-haskell-bugs@haskell.org
| Cc: glasgow-haskell-us...@haskell.org
| 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
| mech...@botik.ru
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