anchor.diff:  {stdenv, fetchurl, writeText, pkgconfig, ocaml, findlib, camlp5, ncurses, lablgtk ? null, csdp ? null}:
   
   let
  -  version = "8.5b2";
  +  version = "8.5rc1";
     coq-version = "8.5";
     buildIde = lablgtk != null;
     ideFlags = if buildIde then "-lablgtkdir ${lablgtk}/lib/ocaml/*/site-lib/lablgtk2 -coqide opt" else "";
  
positive.code:     RM=$(type -tp rm)
      substituteInPlace configure --replace "/bin/uname" "$UNAME"
      substituteInPlace tools/beautify-archive --replace "/bin/rm" "$RM"
      substituteInPlace Makefile.build --replace "ifeq (\$(ARCH),Darwin)" "ifeq (\$(ARCH),Darwinx)"
      ${csdpPatch}
    '';
  
  
negative.code:   inherit ocaml camlp5;
  
    src = fetchurl {
      url = https://coq.inria.fr/distrib/V8.5rc1/files/coq-8.5rc1.tar.gz;
      sha256 = "0n8mb7di9iwg8dgy1xmivf2ajx8kqkrj9mafc32vicn2lbg16q2r";
    };
  
    buildInputs = [ pkgconfig ocaml findlib camlp5 ncurses lablgtk ];
  