simple_rail.py

from typing import Tuple

import numpy as np

from flatland.core.grid.grid4 import Grid4Transitions
from flatland.core.transition_map import GridTransitionMap


def make_simple_rail() -> Tuple[GridTransitionMap, np.array]:
    # We instantiate a very simple rail network on a 7x10 grid:
    #        |
    #        |
    #        |
    # _ _ _ /_\ _ _  _  _ _ _
    #               \ /
    #                |
    #                |
    #                |
    cells = [int('0000000000000000', 2),  # empty cell - Case 0
             int('1000000000100000', 2),  # Case 1 - straight
             int('1001001000100000', 2),  # Case 2 - simple switch
             int('1000010000100001', 2),  # Case 3 - diamond drossing
             int('1001011000100001', 2),  # Case 4 - single slip switch
             int('1100110000110011', 2),  # Case 5 - double slip switch
             int('0101001000000010', 2),  # Case 6 - symmetrical switch
             int('0010000000000000', 2)]  # Case 7 - dead end
    transitions = Grid4Transitions([])
    empty = cells[0]
    dead_end_from_south = cells[7]
    dead_end_from_west = transitions.rotate_transition(dead_end_from_south, 90)
    dead_end_from_north = transitions.rotate_transition(dead_end_from_south, 180)
    dead_end_from_east = transitions.rotate_transition(dead_end_from_south, 270)
    vertical_straight = cells[1]
    horizontal_straight = transitions.rotate_transition(vertical_straight, 90)
    double_switch_south_horizontal_straight = horizontal_straight + cells[6]
    double_switch_north_horizontal_straight = transitions.rotate_transition(
        double_switch_south_horizontal_straight, 180)
    rail_map = np.array(
        [[empty] * 3 + [dead_end_from_south] + [empty] * 6] +
        [[empty] * 3 + [vertical_straight] + [empty] * 6] * 2 +
        [[dead_end_from_east] + [horizontal_straight] * 2 +
         [double_switch_north_horizontal_straight] +
         [horizontal_straight] * 2 + [double_switch_south_horizontal_straight] +
         [horizontal_straight] * 2 + [dead_end_from_west]] +
        [[empty] * 6 + [vertical_straight] + [empty] * 3] * 2 +
        [[empty] * 6 + [dead_end_from_north] + [empty] * 3], dtype=np.uint16)
    rail = GridTransitionMap(width=rail_map.shape[1],
                             height=rail_map.shape[0], transitions=transitions)
    rail.grid = rail_map
    return rail, rail_map