anchor.diff:  # generic builder for Cabal packages
   
  -attrs :
  +{stdenv, fetchurl, lib, ghc, enableLibraryProfiling ? false, ...} :
   {
     mkDerivation =
       transform :
  
positive.code:                 done
                done
  
                ./Setup configure --verbose --prefix="$out" $extraLibDirs $configureFlags
  
                eval "$postConfigure"
              '';
  
negative.code: 
              # We inherit stdenv and ghc so that they can be used
              # in Cabal derivations.
              inherit stdenv ghc;
            };
      in  stdenv.mkDerivation ((rec { f = dtransform f // transform f; }).f);
  }
  