public function is_nan()
    {
        if ($this->q == 0) return true;
        return is_nan($this->p) || is_nan($this->q);
    }
public function is_nan()
    {
        if ($this->q == 0) return true;
        return is_nan($this->p) || is_nan($this->q);
    }
public function is_nan ( ) { if ( $ this -> q == 0 ) return true ; return is_nan ( $ this -> p ) || is_nan ( $ this -> q ) ; }
test if the rational number is NAN

@retval bool
test if the rational number is NAN