anchor.diff:  
       builtins.genericClosure {
         startSet = [{key = rootFile;}];
  -      
  +
         operator =
           {key, ...}:
   
  
positive.code: 
      builtins.genericClosure {
        startSet = [{key = rootFile;}];
        
        operator =
          {key, ...}:
  
  
negative.code:     , extraFiles ? []
      , compressBlanksInIndex ? true
      , packages ? []
      , texPackages ? {}
      , copySources ? false
      }:
  
      assert generatePDF -> !generatePS;
  
      let
        tex = pkgs.texlive.combine texPackages;
      in
  
      pkgs.stdenv.mkDerivation {
        name = "doc";
  
        builder = ./run-latex.sh;
        copyIncludes = ./copy-includes.pl;
  
        inherit rootFile generatePDF generatePS extraFiles
          compressBlanksInIndex copySources;
  
        includes = map (x: [x.key (baseNameOf (toString x.key))])
          (findLaTeXIncludes {inherit rootFile;});
  
        buildInputs = [ tex pkgs.perl ] ++ packages;
      };
  
  
  