sub new 
  {
  # create a new BigInt object from a string or another BigInt object. 
  # see hash keys documented at top

  # the argument could be an object, so avoid ||, && etc on it, this would
  # cause costly overloaded code to be called. The only allowed ops are
  # ref() and defined.

  my ($class,$wanted,$a,$p,$r) = @_;
 
  # avoid numify-calls by not using || on $wanted!
  return $class->bzero($a,$p) if !defined $wanted;	# default to 0
  return $class->copy($wanted,$a,$p,$r)
   if ref($wanted) && $wanted->isa($class);		# MBI or subclass

  $class->import() if $IMPORT == 0;		# make require work
  
  my $self = bless {}, $class;