SQL & PL/SQL

Hi,

I have a function that converts number to binary format which looks like

FUNCTION dec2bin (N in number, bits in number) RETURN varchar2 IS
  binval varchar2(64);
  N2 number := N;
BEGIN
  while ( N2 > 0 ) loop
  binval := mod(N2, 2) || binval;
  N2 := trunc( N2 / 2 );
  end loop;
     binval := LPad(binval,bits,'0');
  return binval;
END dec2bin;

I want to alter this so it works correctly for negative values as well. Please suggest.

Thanks,

Imran.