ANNOUNCE: GHC 6.8.3 Release Candidate

[Don Stewart]

Hello Serge,

I was looking at the cabal file used to build docon, 
I note the current flags are:

   ghc-options:
      -fglasgow-exts -fallow-overlapping-instances 
      -fallow-undecidable-instances
      -fno-warn-overlapping-patterns -fwarn-unused-binds 
      -fwarn-unused-matches -fwarn-unused-imports
      -O
      +RTS -M400m -RTS  
     
Do you gain any performance benefit using:

      -O2 -fvia-C -optc-O2

I'm wondering.

Also, would you be interested in releasing the cabal bundle for docon on
hackage.haskell.org , so it can be easily installed by others?

-- Don

mechvel:
> On Sun, Jun 01, 2008 at 01:13:06AM +0100, Ian Lynagh wrote:
> > 
> > Hi Serge,
> > 
> > On Sat, May 31, 2008 at 12:54:50PM +0400, Serge D. Mechveliani wrote:
> > > This is a bug report for the  ghc candidate of May 27, 2008 
> > > for ghc-6.8.3.
> > > A short program example for this bug candidate is on
> > > 
> > >   http://botik.ru/pub/local/Mechveliani/ghcBugs/candidateMay27-08-bug.zip
> > 
> > Thanks, I've finally tracked this down. The problem is that when you
> > evaluate something like
> >     f ^ 10
> > in 6.8.2 the result was
> >     res
> > while in 6.8.3 it is
> >     1 * res
> > 
> > I think this is actually a bug in your class instances, but I will try
> > to look at http://hackage.haskell.org/trac/ghc/ticket/2306 before 6.8.3
> > which should, as a side-effect, make it work again.
> 
> ??
> Probably, 6.8.3 is wrong.
> Because when  res ::  Num a => a,  1*res  means  
>                                           ((fromInteger 1) :: a) * res  
> in Haskell-98. Right?
> And  (fromInteger n) :: a   can be defined arbitrarily by the programmer.
> For example, DoCon has the instance
>   instance CommutativeRing a => Num (Pol a) 
>     where
>     ...
>     fromInteger _ = error "No  (fromInteger n) :: Pol _ !\
>                           \Apply instead  fromi <samplePolynomial> n."   
> -- something of this kind.
> This is why  res  and  1*res  are not equivalent in Haskell-98 for  
> res :: Num a => a.
> 
> Am I missing something?
> 
> -----------------
> Serge Mechveliani
> mechvel at botik.ru
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