bool PointFilter::check(double* point)
{
  // create a new checker chain
  if(m_changed) {
    createCheckers();
    // mark as unchanged to avoid recreation on further calls
    m_changed = false;
  }
  
  // apply all tests to the point
  Checker* checker = m_checker;
  while(checker) {
    if(checker->test(point)) {
      checker = checker->m_next;
    } else {
      // if even one test fails the point is discarded
      return false;
    }
  }
  // point has passed if all tests returned true
  return true;
}