anchor.diff:  
     meta = {
       description = "The GNU Scientific Library, a large numerical library";
  +    homepage = http://www.gnu.org/software/gsl/;
  +    license = "GPLv3+";
   
       longDescription = ''
         The GNU Scientific Library (GSL) is a numerical library for C
  
positive.code:       fitting.  There are over 1000 functions in total with an
        extensive test suite.
      '';
  
      homepage = http://www.gnu.org/software/gsl/;
      license = "GPLv3+";
  
      maintainers = [ ];
    };
  }
  
negative.code: { fetchurl, stdenv }:
  
  stdenv.mkDerivation rec {
    name = "gsl-1.16";
  
    src = fetchurl {
      url = "mirror://gnu/gsl/${name}.tar.gz";
      sha256 = "0lrgipi0z6559jqh82yx8n4xgnxkhzj46v96dl77hahdp58jzg3k";
    };
  
    # ToDo: there might be more impurities than FMA support check
  