anchor.diff:  
     src = fetchzip {
       url = "http://github.com/OCamlPro/ocp-index/archive/${version}.tar.gz";
  -    sha256 = "173lqbyivwv1zf9ifpxa9f8m2y3kybzs3idrwyzy824ixdqv2fww";
  +    sha256 = "0cz0bz5nisc5r23b1w07q2bl489gd09mg8rp9kyq9m6rj669b18l";
     };
  +
  +  patches = optional (versionAtLeast (getVersion ocaml) "4.02") patch402;
   
     buildInputs = [ ocaml findlib ocpBuild opam cmdliner ncurses re libev ]
     ++ optional (versionAtLeast (getVersion lambdaTerm) "1.7") lambdaTerm;
  
positive.code: assert versionAtLeast (getVersion ocpBuild) "1.99.6-beta";
  assert versionAtLeast (getVersion ocpIndent) "1.4.2";
  
  let version = "1.1.1"; in
  
  stdenv.mkDerivation {
  
  
negative.code: { stdenv, fetchurl, fetchzip, ocaml, findlib, ocpBuild, ocpIndent, opam, cmdliner, ncurses, re, lambdaTerm, libev }:
  
  let inherit (stdenv.lib) getVersion versionAtLeast optional; in
  
  