anchor.diff: -{ stdenv, fetchurl, ncurses, x11 }:
  +{ stdenv, fetchurl, ncurses, buildEnv, libX11, xproto }:
   
   let
      useX11 = !stdenv.isArm && !stdenv.isMips;
  
positive.code:   };
  
    prefixKey = "-prefix ";
    configureFlags = ["-no-tk"] ++ optionals useX11 [ "-x11lib" x11 ];
    buildFlags = "world" + optionalString useNativeCompilers " bootstrap world.opt";
    buildInputs = [ncurses] ++ optionals useX11 [ x11 ];
    installTargets = "install" + optionalString useNativeCompilers " installopt";
    preConfigure = ''
      CAT=$(type -tp cat)
  
negative.code: 
  stdenv.mkDerivation rec {
  
    x11env = buildEnv { name = "x11env"; paths = [libX11 xproto]; };
    x11lib = x11env + "/lib";
    x11inc = x11env + "/include";
  
    name = "ocaml-4.01.0";
  
    src = fetchurl {
  