anchor.diff:    # The bleeding edge.
     nixUnstable = makeOverridable (import ../tools/package-management/nix/unstable.nix) {
       inherit fetchurl stdenv perl curl bzip2 openssl;
  -    aterm = aterm242fixes;
  +    aterm = aterm25;
       storeDir = getPkgConfig "nix" "storeDir" "/nix/store";
       stateDir = getPkgConfig "nix" "stateDir" "/nix/var";
     };
  
positive.code:       inherit fetchurl stdenv perl curl bzip2 openssl src preConfigure automake
          autoconf libtool configureFlags enableScripts lib bison libxml2;
        flex = flex2533;
        aterm = aterm242fixes;
        db4 = db45;
        inherit docbook5_xsl libxslt docbook5 docbook_xml_dtd_43 w3m;
      };
  
negative.code:       inherit fetchurl stdenv perl curl bzip2 openssl bison;
        inherit libtool automake autoconf docbook5 docbook5_xsl libxslt docbook_xml_dtd_43 w3m;
  
        aterm = aterm25;
        db4 = db45;
  
        flex = flex2533;
  