anchor.diff:      inherit pname version;
   
       isHaskellLibrary = hasActiveLibrary;
  +
  +    # TODO: ask why the split outputs are configurable at all?
  +    # TODO: include tests for split if possible
  +    # Given the haskell package, returns
  +    # the directory containing the haddock documentation.
  +    # `null' if no haddock documentation was built.
  +    # TODO: fetch the self from the fixpoint instead
  +    haddockDir = self: if doHaddock then "${docdir self.doc}/html" else null;
   
       env = stdenv.mkDerivation {
         name = "interactive-${pname}-${version}-environment";
  
positive.code:     ''}
  
      ${optionalString enableSeparateDocOutput ''
      for x in $doc/share/doc/html/src/*.html; do
        remove-references-to -t $out $x
      done
      mkdir -p $doc
  
negative.code:                         then "package-db"
                          else "package-conf";
  
    # the target dir for haddock documentation
    docdir = docoutput: docoutput + "/share/doc";
  
    newCabalFileUrl = "http://hackage.haskell.org/package/${pname}-${version}/revision/${revision}.cabal";
    newCabalFile = fetchurl {
      url = newCabalFileUrl;
  