Re: [Haskell-cafe] ANN: json-0.4.1

13 Jan 2009

      Thanks Bas for the helpful & clear advice.

While I'm not on top of it yet why some installs of 6.10.1 experience 
this build
failure, but others don't, I've put together an updated .cabal file + 
source dist
that I hope gets at it. It's available from

   http://www.galois.com/~sof/json-0.4.1.tar.gz

I've pointed Alex at this bundle earlier, but if others that have run 
into the same
problem could test using above bits and see if that fixes it, that'd be 
great.

If cool, I'll upload the bits to hackage. My apologies if this is 
breaking people's
cabal builds at the moment.

cheers
--sigbjorn

On 1/13/2009 11:58, Bas van Dijk wrote:
...
On Tue, Jan 13, 2009 at 8:47 PM, Alex Ott  wrote:
...
Hello
...
...
...
...
> "SF" == Sigbjorn Finne writes:
>               
 SF> Hi, a new release of the 'json' package is now available via hackage,
 SF> version 0.4.1
SF>   http://hackage.haskell.org/cgi-bin/hackage-scripts/package/json
I tried to upgrade it via cabal on mac os x & linux (both use ghc 6.10.1)
and it fails with
Building json-0.4.1...
Text/JSON/Generic.hs:33:7:
   Could not find module `Data.Generics':
     it was found in multiple packages: base-3.0.3.0 syb
cabal: Error: some packages failed to install:
json-0.4.1 failed during the building phase. The exception was:
exit: ExitFailure 1
The standard solution for this is to add a cabal flag that controls
wether to depend on base-4 or base-3:
------------------------------------------------------
flag small_base
  description:          Choose the new smaller, split-up base package.
Library
  if flag(small_base)
    Build-Depends:      base == 4.*, syb
    CPP-Options:        -DBASE_4
  else
    Build-Depends:      base == 3.*
------------------------------------------------------
And use some CPP in your modules like this:
------------------------------------------------------
{-# LANGUAGE CPP #-}
#ifdef BASE_4
import Data.Data (Data)
#else
import Data.Generics (Data)
#endif
------------------------------------------------------
See for example how I do it in http://code.haskell.org/Stream
regards,
Bas