[Haskell-cafe] Error when installing RSA (for yesod) with GHC 7.2.1

[Yves Parès]

Okay, so the problem is with cabal-install.
I'd don't verily need ghc 7.2, I think I'll just stick to 7.0.4 unti
cabal-install is updated, it will be simpler.

2011/10/24 Daniel Fischer <daniel.is.fischer at googlemail.com>

> On Monday 24 October 2011, 23:13:32, Yves Parès wrote:
> > I'm using GHC 7.2.1 and cabal-install 0.8 (Cabal 1.8.0.2), and when
> > "cabal install rsa"
>
> >
> > Apparently it's an instance being declared twice.
> > However RSA hackage page states that it compiles under GHC 7.2:
> > http://hackage.haskell.org/package/RSA
>
> The instance in the rsa package is guarded by a Cabal MIN_VERSION macro:
>
> #if !MIN_VERSION_random(1,0,1)
> instance Random Word8 where
>  randomR (a,b) g = let aI::Int = fromIntegral a
>                        bI::Int = fromIntegral b
>                        (x, g') = randomR (aI, bI) g
>                    in (fromIntegral x, g')
>  random          = randomR (minBound, maxBound)
> #endif
>
> Unfortunately, that macro was broken in some Cabal versions, among them
> 1.8.0.2, so the negated check goes wrong (#if !(MIN_...) would work).
> [As a quickfix for this package, you could edit the source, but you'll
> probably come across more macro problems later.]
>
> Build yourself a new cabal-install.
> If you use 7.2.1 for that, the recipe at https://gist.github.com/1169332
> tells you what you have to change.
> If you have an older ghc still available, the vanilla procedure should work
> with that (if you're using the old 6.12.* with the Cabal-1.8.0.2, first
> install a later Cabal version, 1.8.0.6 works).
>
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