anchor.diff:  
                 ensureDir $out/nix-support
                 ln -s $out/nix-support/propagated-build-inputs $out/nix-support/propagated-user-env-packages
  -              
  +
                 eval "$postInstall"
               '';
             };
       in  attrs.stdenv.mkDerivation ((rec { f = dtransform f // transform f; }).f);
  -} 
  +}
  
positive.code: 
                ./Setup build
  
                eval "$postBuild"
              '';
  
  	    # installs via Cabal; creates a registration file for nix-support
  	    # so that the package can be used in other Haskell-builds; also
  	    # adds all propagated build inputs to the user environment packages
              installPhase = ''
                eval "$preInstall"
  
  
negative.code: 
              # pname should be defined by the client to be the package basename
              # version should be defined by the client to be the package version
  
              # fname is the internal full name of the package
              fname = "${self.pname}-${self.version}";
  
              # name is the external full name of the package; usually we prefix
              # all packages with haskell- to avoid name clashes for libraries;
              # if that is not desired (for applications), name can be set to
              # fname.
              name = "haskell-${self.pname}-ghc${attrs.ghc.ghc.version}-${self.version}";
  
              # the default download location for Cabal packages is Hackage,
              # you still have to specify the checksum
  