anchor.diff:    # issues with ntl -- https://github.com/wbhart/flint2/issues/487
     NIX_CXXSTDLIB_COMPILE = "-std=c++11";
   
  -  patches = [
  -    (fetchpatch {
  -      # Always produce libflint.so.MAJOR; will be included in the next flint version
  -      # See https://github.com/wbhart/flint2/pull/347
  -      url = "https://github.com/wbhart/flint2/commit/49fbcd8f736f847d3f9667f9f7d5567ef4550ecb.patch";
  -      sha256 = "09w09bpq85kjf752bd3y3i5lvy59b8xjiy7qmrcxzibx2a21pj73";
  -    })
  -  ];
     doCheck = true;
     meta = {
       inherit version;
  
positive.code: { lib, stdenv
  , fetchurl
  , fetchpatch
  , gmp
  , mpir
  , mpfr
  
negative.code: 
  stdenv.mkDerivation rec {
    pname = "flint";
    version = "2.7.1";
    src = fetchurl {
      url = "http://www.flintlib.org/flint-${version}.tar.gz";
      sha256 = "07j8r96kdzp19cy3a5yvpjxf90mkd6103yr2n42qmpv7mgcjyvhq";
    };
    buildInputs = [
      gmp
  