use overload
  q("") => 'to_string',
  '0+' => 'to_num',
  '+' => 'add',
  '*' => 'mult',
  '-' => 'subtract',
  '/' => 'div',
  '<=>' => 'compare',
  'cmp' => 'compare',
  fallback => 1;






=head2 compare

Compare a fraction object with a value. Return -1, 0, 1 depending on if object is less than, equal to, or greater than the value.

The first parameter is a fraction object. The second parameter is either
another fraction object or a number (eg 0.25) or a string (eg '1/4').

=cut

sub compare {
  my ($l, $r, $rev) = @_;
  my $x = $l->to_num;
  my $y;
  if( UNIVERSAL::isa($r, ref $l) ){
    $y = $r->to_num;
  }elsif( my $r2 = (ref $l)->new($r) ){
    $y = $r2->to_num;
  }else{
    $y = $r;
  }
  return 0 if $x == $y;
  return ($rev?-1:1) *  ($x < $y ? -1 : 1);
}