Write a program that takes in commands and moves one or more robots around Mars.

• The world should be modelled as a grid with size m x n
• Your program should read the input, update the robots, and print out the final states of the robots
• Each robot has a position (x, y), and an orientation (N, E, S, W)
• Each robot can move forward one space (F), rotate left by 90 degrees (L), or rotate right by 90 degrees (R)
• If a robot moves off the grid, it is marked as ‘lost’ and its last valid grid position and orientation is recorded
• Going from x -> x + 1 is in the easterly direction, and y -> y + 1 is in the northerly direction. i.e. (0, 0) represents the south-west corner of the grid

The input takes the form:

4 8
(2, 3, E) LFRFF
(0, 2, N) FFLFRFF

The first line of the input ‘4 8’ specifies the size of the grid. The subsequent lines each represent the initial state and commands for a single robot. (0, 2, N) specifies the initial state of the form (x, y, orientation). FFLFRFF represents the sequence of movement commands for the robot.

The output should take the form:

(4, 4, E)
(0, 4, W) LOST

Each line represents the final position and orientation of the robots of the form (x, y, orientation) and optionally whether the robot was lost.

Another example for the input:

4 8
(2, 3, N) FLLFR
(1, 0, S) FFRLF

The output would be:

(2, 3, W)
(1, 0, S) LOST

Run mix test or mix test --trace.

Run mix dialyzer.

Run mix escript.build

$ ./mars_rover <<EOF
4 8
(2, 3, N) FLLFR
(1, 0, S) FFRLF
EOF

Output:

(2, 3, W)
(1, 0, S) LOST

Alternatively:

cat instructions.txt | ./mars_rover

• Better CLI interface
• Process each robot concurrently?
• Collision detection?
• Property-based testing?
• More granular directions, rather than just compass headings
• Some sort of graphical interface?

If available in Hex, the package can be installed by adding mars_rover to your list of dependencies in mix.exs:

def deps do
  [
    {:mars_rover, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/mars_rover.