anchor.diff:  { lib, stdenv
   , fetchurl
  -, fetchpatch
   , gmp
   , mpir
   , mpfr
  
positive.code: 
  stdenv.mkDerivation rec {
    pname = "flint";
    version = "2.5.2"; # remove libflint.so.MAJOR patch when updating
    src = fetchurl {
      url = "http://www.flintlib.org/flint-${version}.tar.gz";
      sha256 = "11syazv1a8rrnac3wj3hnyhhflpqcmq02q8pqk2m6g2k6h0gxwfb";
    };
    buildInputs = [
      gmp
  
negative.code:   # issues with ntl -- https://github.com/wbhart/flint2/issues/487
    NIX_CXXSTDLIB_COMPILE = "-std=c++11";
  
    doCheck = true;
    meta = {
      inherit version;
  