anchor.diff:    inherit (stdenv.lib) optionals versionAtLeast;
   
     pname = "vg";
  -  version = "0.9.3";
  +  version = "0.9.4";
     webpage = "https://erratique.ch/software/${pname}";
   in
   
  
positive.code: 
    src = fetchurl {
      url = "${webpage}/releases/${pname}-${version}.tbz";
      sha256 = "0jj5hrqxdb6yyplnz0r7am4mbjzgcn876qp7sqs2x93a97fk6lwd";
    };
  
    buildInputs = [ ocaml findlib ocamlbuild topkg ];
  
    propagatedBuildInputs = [ uchar result gg ]
                            ++ optionals pdfBackend [ uutf otfm ]
                            ++ optionals htmlcBackend [ js_of_ocaml js_of_ocaml-ocamlbuild js_of_ocaml-ppx ];
  
    buildPhase = topkg.buildPhase
      + " --with-uutf ${boolToString pdfBackend}"
  
negative.code: { stdenv, lib, fetchurl, ocaml, findlib, ocamlbuild, topkg
  , uchar, result, gg, uutf, otfm
  , js_of_ocaml, js_of_ocaml-ppx,
    pdfBackend ? true, # depends on uutf and otfm
    htmlcBackend ? true # depends on js_of_ocaml
  }:
  