SORT_BY_VALUE, //!< Sort the list based on the value of the item.

		SORT_BY_ITEM,  //!< Sort the list based on the item itself.

	AIAbstractListSorter *sorter; //!< Sorting algorithm

	SorterType sorter_type;       //!< Sorting type

	bool sort_ascending;          //!< Whether to sort ascending or descending

	bool initialized;             //!< Whether an iteration has been started

	int modifications;            //!< Number of modification that has been done. To prevent changing data while valuating.

	typedef std::set<int32> AIItemList;                       //!< The list of items inside the bucket

	typedef std::map<int32, AIItemList> AIAbstractListBucket; //!< The bucket list per value

	typedef std::map<int32, int32> AIAbstractListMap;         //!< List per item

	AIAbstractListMap items;           //!< The items in the list

	AIAbstractListBucket buckets;      //!< The items in the list, sorted by value

		AT_SMALL         =   0, //!< The small airport.

		AT_LARGE         =   1, //!< The large airport.

		AT_METROPOLITAN  =   3, //!< The metropolitan airport.

		AT_INTERNATIONAL =   4, //!< The international airport.

		AT_COMMUTER      =   5, //!< The commuter airport.

		AT_INTERCON      =   7, //!< The intercontinental airport.

		AT_HELIPORT      =   2, //!< The heliport.

		AT_HELISTATION   =   8, //!< The helistation.

		AT_HELIDEPOT     =   6, //!< The helidepot.

		AT_INVALID       = 255, //!< Invalid airport.

		PT_HELICOPTER    =   0, //!< A helicopter.

		PT_SMALL_PLANE   =   1, //!< A small plane.

		PT_BIG_PLANE     =   3, //!< A big plane.

		PT_INVALID       =  -1, //!< An invalid PlaneType

		STATION_NEW = 0xFFFD,           //!< Build a new station

		STATION_JOIN_ADJACENT = 0xFFFE, //!< Join an neighbouring station if one exists

		STATION_INVALID = 0xFFFF,       //!< Invalid station id.

		CC_PASSENGERS   = 1 <<  0, //!< Passengers. Cargos of this class appear at bus stops. Cargos not of this class appear at truck stops.

		CC_MAIL         = 1 <<  1, //!< Mail

		CC_EXPRESS      = 1 <<  2, //!< Express cargo (Goods, Food, Candy, but also possible for passengers)

		CC_ARMOURED     = 1 <<  3, //!< Armoured cargo (Valuables, Gold, Diamonds)

		CC_BULK         = 1 <<  4, //!< Bulk cargo (Coal, Grain etc., Ores, Fruit)

		CC_PIECE_GOODS  = 1 <<  5, //!< Piece goods (Livestock, Wood, Steel, Paper)

		CC_LIQUID       = 1 <<  6, //!< Liquids (Oil, Water, Rubber)

		CC_REFRIGERATED = 1 <<  7, //!< Refrigerated cargo (Food, Fruit)

		CC_HAZARDOUS    = 1 <<  8, //!< Hazardous cargo (Nuclear Fuel, Explosives, etc.)

		CC_COVERED      = 1 <<  9, //!< Covered/Sheltered Freight (Transporation in Box Vans, Silo Wagons, etc.)

		TE_NONE       = 0, //!< This cargo has no effect on a town

		TE_PASSENGERS = 1, //!< This cargo supplies passengers to a town

		TE_MAIL       = 2, //!< This cargo supplies mail to a town

		TE_GOODS      = 3, //!< This cargo supplies goods to a town

		TE_WATER      = 4, //!< This cargo supplies water to a town

		TE_FOOD       = 5, //!< This cargo supplies food to a town

		COMPANY_FIRST   = 0,               //!< The first available company.

		COMPANY_LAST    = ::MAX_COMPANIES, //!< The last available company.

		COMPANY_SELF    = 254,             //!< Constant that gets resolved to the correct company index for your company.

		COMPANY_INVALID = -1,              //!< An invalid company.

		GENDER_MALE,         //!< A male person.

		GENDER_FEMALE,       //!< A female person.

		GENDER_INVALID = -1, //!< An invalid gender.

		ERR_CAT_NONE = 0, //!< Error messages not related to any category.

		ERR_CAT_GENERAL,  //!< Error messages related to general things.

		ERR_CAT_VEHICLE,  //!< Error messages related to building / maintaining vehicles.

		ERR_CAT_STATION,  //!< Error messages related to building / maintaining stations.

		ERR_CAT_BRIDGE,   //!< Error messages related to building / removing bridges.

		ERR_CAT_TUNNEL,   //!< Error messages related to building / removing tunnels.

		ERR_CAT_TILE,     //!< Error messages related to raising / lowering and demolishing tiles.

		ERR_CAT_SIGN,     //!< Error messages related to building / removing signs.

		ERR_CAT_RAIL,     //!< Error messages related to building / maintaining rails.

		ERR_CAT_ROAD,     //!< Error messages related to building / maintaining roads.

		ERR_CAT_ORDER,    //!< Error messages related to managing orders.

		ERR_CAT_MARINE,   //!< Error messages related to building / removing ships, docks and channels.

		ERR_CAT_WAYPOINT, //!< Error messages related to building / maintaining waypoints.

		CRASH_TRAIN,                //!< Two trains collided

		CRASH_RV_LEVEL_CROSSING,    //!< Road vehicle got under a train

		CRASH_RV_UFO,               //!< Road vehicle got under a landing ufo

		CRASH_PLANE_LANDING,        //!< Plane crashed on landing

		CRASH_AIRCRAFT_NO_AIRPORT,  //!< Aircraft crashed after it found not a single airport for landing

		CRASH_FLOODED,              //!< Vehicle was flooded

		GROUP_ALL = 0xFFFD,     //!< All vehicles are in this group.

		GROUP_DEFAULT = 0xFFFE, //!< Vehicles not put in any other group are in this one.

		GROUP_INVALID = 0xFFFF, //!< An invalid group id.

		INDUSTRYTYPE_UNKNOWN = 0xFE, //!< Unknown/unspecific industrytype. (Usable for AIRail::BuildNewGRFRailStation())

		INDUSTRYTYPE_TOWN    = 0xFF, //!< No industry, but town. (Usable for AIRail::BuildNewGRFRailStation())

		AICONFIG_NONE,    //!< Normal setting.

		AICONFIG_RANDOM,  //!< When randomizing the AI, pick any value between min_value and max_value.

		AICONFIG_BOOLEAN, //!< This value is a boolean (either 0 (false) or 1 (true) ).

		AICONFIG_INGAME,  //!< This setting can be changed while the AI is running.

		LOG_SQ_ERROR = 0, //!< Squirrel printed an error.

		LOG_ERROR = 1,    //!< User printed an error.

		LOG_SQ_INFO = 2,  //!< Squirrel printed some info.

		LOG_WARNING = 3,  //!< User printed some warning.

		LOG_INFO = 4,     //!< User printed some info.

		char **lines;           //!< The log-lines.

		AILog::AILogType *type; //!< Per line, which type of log it was.

		int count;              //!< Total amount of log-lines possible.

		int pos;                //!< Current position in lines.

		int used;               //!< Total amount of used log-lines.

	static const int TILE_INVALID = (int)INVALID_TILE; //!< Invalid TileIndex.

		BT_DOCK,  //!< Build a dock

		BT_DEPOT, //!< Build a ship depot

		BT_BUOY,  //!< Build a buoy

		OC_LOAD_PERCENTAGE,  //!< Skip based on the amount of load, value is in tons.

		OC_RELIABILITY,      //!< Skip based on the reliability, value is percent (0..100).

		OC_MAX_SPEED,        //!< Skip based on the maximum speed, value is in OpenTTD's internal speed unit, see AIEngine::GetMaxSpeed.

		OC_AGE,              //!< Skip based on the age, value is in years.

		OC_REQUIRES_SERVICE, //!< Skip when the vehicle requires service, no value.

		OC_UNCONDITIONALLY,  //!< Always skip, no compare function, no value.

		OC_INVALID = -1,     //!< An invalid condition, do not use.

		CF_EQUALS,       //!< Skip if both values are equal

		CF_NOT_EQUALS,   //!< Skip if both values are not equal

		CF_LESS_THAN,    //!< Skip if the value is less than the limit

		CF_LESS_EQUALS,  //!< Skip if the value is less or equal to the limit

		CF_MORE_THAN,    //!< Skip if the value is more than the limit

		CF_MORE_EQUALS,  //!< Skip if the value is more or equal to the limit

		CF_IS_TRUE,      //!< Skip if the variable is true

		CF_IS_FALSE,     //!< Skip if the variable is false

		CF_INVALID = -1, //!< Invalid compare function, do not use.

		ORDER_CURRENT = 0xFF, //!< Constant that gets resolved to the current order.

		ORDER_INVALID = -1,   //!< An invalid order.

		STOPLOCATION_NEAR,         //!< Stop the train as soon as it's completely in the station

		STOPLOCATION_MIDDLE,       //!< Stop the train in the middle of the station

		STOPLOCATION_FAR,          //!< Stop the train at the far end of the station

		STOPLOCATION_INVALID = -1, //!< An invalid stop location

	Track track;        //!< The track that will be taken to travel.

	Trackdir trackdir;  //!< The Trackdir belonging to that track.

	uint signal_cycles; //!< How many times the signal should be cycled in order to build it in the correct direction.

static const int NUM_TRACK_DIRECTIONS = 3; //!< The number of directions you can go when entering a tile.

		RAILTYPE_INVALID  = 0xFF, //!< Invalid RailType.

		RAILTRACK_NE_SW   = 1 << 0, //!< Track along the x-axis (north-east to south-west).

		RAILTRACK_NW_SE   = 1 << 1, //!< Track along the y-axis (north-west to south-east).

		RAILTRACK_NW_NE   = 1 << 2, //!< Track in the upper corner of the tile (north).

		RAILTRACK_SW_SE   = 1 << 3, //!< Track in the lower corner of the tile (south).

		RAILTRACK_NW_SW   = 1 << 4, //!< Track in the left corner of the tile (west).

		RAILTRACK_NE_SE   = 1 << 5, //!< Track in the right corner of the tile (east).

		RAILTRACK_INVALID = 0xFF,   //!< Flag for an invalid track.

		SIGNALTYPE_NORMAL        = 0, //!< Normal signal.

		SIGNALTYPE_ENTRY         = 1, //!< Entry presignal.

		SIGNALTYPE_EXIT          = 2, //!< Exit signal.

		SIGNALTYPE_COMBO         = 3, //!< Combo signal.

		SIGNALTYPE_PBS           = 4, //!< Normal PBS signal.

		SIGNALTYPE_PBS_ONEWAY    = 5, //!< No-entry PBS signal.

		SIGNALTYPE_TWOWAY        = 8, //!< Bit mask for twoway signal.

		SIGNALTYPE_NORMAL_TWOWAY = SIGNALTYPE_NORMAL | SIGNALTYPE_TWOWAY, //!< Normal twoway signal.

		SIGNALTYPE_ENTRY_TWOWAY  = SIGNALTYPE_ENTRY | SIGNALTYPE_TWOWAY,  //!< Entry twoway signal.

		SIGNALTYPE_EXIT_TWOWAY   = SIGNALTYPE_EXIT | SIGNALTYPE_TWOWAY,   //!< Exit twoway signal.

		SIGNALTYPE_COMBO_TWOWAY  = SIGNALTYPE_COMBO | SIGNALTYPE_TWOWAY,  //!< Combo twoway signal.

		SIGNALTYPE_NONE          = 0xFF, //!< No signal.

		BT_TRACK,    //!< Build a track

		BT_SIGNAL,   //!< Build a signal

		BT_DEPOT,    //!< Build a depot

		BT_STATION,  //!< Build a station

		BT_WAYPOINT, //!< Build a rail waypoint

		ROADTYPE_ROAD = 0, //!< Build road objects.

		ROADTYPE_TRAM = 1, //!< Build tram objects.

		ROADTYPE_INVALID = -1, //!< Invalid RoadType.

		ROADVEHTYPE_BUS,   //!< Build objects useable for busses and passenger trams

		ROADVEHTYPE_TRUCK, //!< Build objects useable for trucks and cargo trams

		BT_ROAD,       //!< Build a piece of road

		BT_DEPOT,      //!< Build a road depot

		BT_BUS_STOP,   //!< Build a bus stop

		BT_TRUCK_STOP, //!< Build a truck stop

		STATION_TRAIN      = 0x01, //!< Train station

		STATION_TRUCK_STOP = 0x02, //!< Truck station

		STATION_BUS_STOP   = 0x04, //!< Bus station

		STATION_AIRPORT    = 0x08, //!< Airport

		STATION_DOCK       = 0x10, //!< Dock

		STATION_ANY        = 0x1F, //!< All station types

		SPT_INDUSTRY =    0, //!< Subsidy participant is an industry

		SPT_TOWN     =    1, //!< Subsidy participant is a town

		SPT_INVALID  = 0xFF, //!< Invalid/unknown participant type

		CORNER_W       = 0,      //!< West corner

		CORNER_S       = 1,      //!< South corner

		CORNER_E       = 2,      //!< East corner

		CORNER_N       = 3,      //!< North corner

		SLOPE_FLAT     = 0x00,                                  //!< A flat tile

		SLOPE_W        = 1 << CORNER_W,                         //!< The west corner of the tile is raised

		SLOPE_S        = 1 << CORNER_S,                         //!< The south corner of the tile is raised

		SLOPE_E        = 1 << CORNER_E,                         //!< The east corner of the tile is raised

		SLOPE_N        = 1 << CORNER_N,                         //!< The north corner of the tile is raised

		SLOPE_STEEP    = 0x10,                                  //!< Indicates the slope is steep (The corner opposite of the not-raised corner is raised two times)

		SLOPE_NW       = SLOPE_N | SLOPE_W,                     //!< North and west corner are raised

		SLOPE_SW       = SLOPE_S | SLOPE_W,                     //!< South and west corner are raised

		SLOPE_SE       = SLOPE_S | SLOPE_E,                     //!< South and east corner are raised

		SLOPE_NE       = SLOPE_N | SLOPE_E,                     //!< North and east corner are raised

		SLOPE_EW       = SLOPE_E | SLOPE_W,                     //!< East and west corner are raised

		SLOPE_NS       = SLOPE_N | SLOPE_S,                     //!< North and south corner are raised

		SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W, //!< Bit mask containing all 'simple' slopes. Does not appear as a slope.

		SLOPE_NWS      = SLOPE_N | SLOPE_W | SLOPE_S,           //!< North, west and south corner are raised

		SLOPE_WSE      = SLOPE_W | SLOPE_S | SLOPE_E,           //!< West, south and east corner are raised

		SLOPE_SEN      = SLOPE_S | SLOPE_E | SLOPE_N,           //!< South, east and north corner are raised

		SLOPE_ENW      = SLOPE_E | SLOPE_N | SLOPE_W,           //!< East, north and west corner are raised

		SLOPE_STEEP_W  = SLOPE_STEEP | SLOPE_NWS,               //!< A steep slope falling to east (from west)

		SLOPE_STEEP_S  = SLOPE_STEEP | SLOPE_WSE,               //!< A steep slope falling to north (from south)

		SLOPE_STEEP_E  = SLOPE_STEEP | SLOPE_SEN,               //!< A steep slope falling to west (from east)

		SLOPE_STEEP_N  = SLOPE_STEEP | SLOPE_ENW,               //!< A steep slope falling to south (from north)

		SLOPE_INVALID  = 0xFFFF,                                //!< An invalid slope

		TRANSPORT_RAIL    =  0, //!< Tile with rail.

		TRANSPORT_ROAD    =  1, //!< Tile with road.

		TRANSPORT_WATER   =  2, //!< Tile with navigable waterways.

		TRANSPORT_AIR     =  3, //!< Tile with airport.

		TRANSPORT_INVALID = -1, //!< Tile without any transport type.

		BT_FOUNDATION,   //!< Build a foundation under something

		BT_TERRAFORM,    //!< Terraform

		BT_BUILD_TREES,  //!< Build trees

		BT_CLEAR_GRASS,  //!< Clear a tile with just grass

		BT_CLEAR_ROUGH,  //!< Clear a rough tile

		BT_CLEAR_ROCKY,  //!< Clear a tile with rocks

		BT_CLEAR_FIELDS, //!< Clear a tile with farm fields

		BT_CLEAR_HOUSE,  //!< Clear a tile with a house

		TOWN_RATING_NONE,         //!< The company got no rating in the town.

		TOWN_RATING_APPALLING,    //!< The company got an appalling rating in the town .

		TOWN_RATING_VERY_POOR,    //!< The company got an very poor rating in the town.

		TOWN_RATING_POOR,         //!< The company got an poor rating in the town.

		TOWN_RATING_MEDIOCRE,     //!< The company got an mediocre rating in the town.

		TOWN_RATING_GOOD,         //!< The company got an good rating in the town.

		TOWN_RATING_VERY_GOOD,    //!< The company got an very good rating in the town.

		TOWN_RATING_EXCELLENT,    //!< The company got an excellent rating in the town.

		TOWN_RATING_OUTSTANDING,  //!< The company got an outstanding rating in the town.

		TOWN_RATING_INVALID = -1, //!< The town rating for invalid towns/companies.

		ROAD_LAYOUT_ORIGINAL,     //!< Original algorithm (min. 1 distance between roads).

		ROAD_LAYOUT_BETTER_ROADS, //!< Extended original algorithm (min. 2 distance between roads).

		ROAD_LAYOUT_2x2,          //!< Geometric 2x2 grid algorithm

		ROAD_LAYOUT_3x3,          //!< Geometric 3x3 grid algorithm

		ROAD_LAYOUT_INVALID = -1, //!< The layout for invalid towns.