Dear GHC developers, I have tested ghc-7.0.0.20100924 on Debian Linux, i386-family on making it by ghc-6.12.3, on the DoCon test, -- with skipping profiling. There are visible the following changes in GHC: (1) Usage of ./Main +RTS .. -RTS needs linking with -rtsopts (2) ghc-6.12.2 compiles docon-2.11 (download it via http://haskell.org/ghc/docon/ and follow install.txt ) and ghc-7.0.0.20100924 cannot. It declares ... DPair.hs:316:35: Couldn't match type `b' with `a' `b' is a rigid type variable bound by the instance declaration at DPair.hs:222:38 `a' is a rigid type variable bound by the instance declaration at DPair.hs:222:23 In the first argument of `restore', namely `zrB' In the expression: restore zrB bs qB' In an equation for `qB': qB = restore zrB bs qB' (3) I also tried docon-2.12 (which differs very slightly from docon-2.11 and which I can provide if asked). ghc-6.12.3 makes it and runs the test successfully. Compiling it by ghc-7.0.0.20100924 stops (close to end) at Pol3_.hs at the fragment of --------------------------------------------------------------------- instance (LinSolvRing (Pol a), CommutativeRing a) => 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' ... ---------------------------------------------------------------- It declares that the line of `s' =' needs (EuclideanRing a) and that it cannot deduce it. I think, for the need of this particular application it is indeed better to change the context to `EuclideanRing a =>' (probably, the initial complicated context was forced by old GHC). After changing it to `EuclideanRing a =>', ghc-7.0.0.20100924 makes docon-2.12 and runs the test successfully. You see, the points (2) and (3) present a certain question about the compler. I wonder wich complier is more correct. (Recall also that Docon uses an extension with overlapping instances, multiparametric classes, and such). (4) At the docon-2.12 test made under -O, ghc-7.0.0.20100924 shows the time 3.9 sec instead of 3.3 sec of ghc-6.12.3. Regards, ----------------- Serge Mechveliani mechvel@botik.ru