mixed   query_door( mixed dest )
{
    mixed   bing;

    if( (bing = door_control[ dest ]) )
	if( !pointerp( bing ) )
	    return bing;
    if( objectp( dest ) )
	if( (bing = door_control[ file_name( dest ) ]) )
	    if( !pointerp( bing ) )
		return bing;
    return 0;
}