anchor.diff:  
     nativeBuildInputs = [ perl pkgconfig ];
   
  -  buildInputs = [ openssl libxslt curl pcre libxml2 ]
  +  buildInputs = [ openssl libxslt curl pcre libxml2 gmp ]
       ++ stdenv.lib.optional withMysql mysql.connector-c
       ++ stdenv.lib.optional withSqlite sqlite
       ++ stdenv.lib.optional withPostgresql postgresql
  
positive.code: { stdenv, fetchurl, pkgconfig, openssl, libxslt, perl
  , curl, pcre, libxml2, librdf_rasqal
  , mysql, withMysql ? false
  , postgresql, withPostgresql ? false
  , sqlite, withSqlite ? true
  
negative.code: 
    meta = {
      homepage = http://librdf.org/;
      platforms = stdenv.lib.platforms.unix;
    };
  }
  