anchor.diff:  { stdenv, fetchFromGitHub, coq }:
   
  -let param =
  +let params =
     {
       "8.6" = {
         rev = "v8.6.0";
  
positive.code:   };
  
    passthru = {
      compatibleCoqVersions = v: builtins.elem v [ "8.6" "8.7" ];
    };
  }
  
negative.code:       rev = "V8.8+beta1";
        sha256 = "1ymxyrvjygscxkfj3qkq66skl3vdjhb670rzvsvgmwrjkrakjnfg";
      };
    };
    param = params."${coq.coq-version}"
  ; in
  
  stdenv.mkDerivation rec {
  