Add robot-simulator exercise

[ageron]

This exercise might be a good candidate for another opaque type. The stub currently looks like this:

module [create, move]

Direction : [North, East, South, West]
Robot : { x : I64, y : I64, direction : Direction }

create : { x ? I64, y ? I64, direction ? Direction } -> Robot
create = \{ x ? 0, y ? 0, direction ? North } ->
    crash "Please implement the 'create' function"

move : Robot, Str -> Robot
move = \robot, instructions ->
    crash "Please implement the 'move' function"

We could instead replace it with this:

module [create, move]

Direction : [North, East, South, West]
Robot := { x : I64, y : I64, dx : I64, dy : I64 }

create : { x ? I64, y ? I64, direction ? Direction } -> Robot
create = \{ x ? 0, y ? 0, direction ? North } ->
    crash "Please implement the 'create' function"

toRecord : Robot -> { x : I64, y : I64, direction : Direction }
toRecord = \robot ->
    crash "Please implement the 'toRecord' function"

move : Robot, Str -> Robot
move = \robot, instructions ->
    crash "Please implement the 'move' function"

The tests would look like this:

expect
    robot = create { direction: West }
    result = robot |> move "R" |> toRecord
    result == { x: 0, y: 0, direction: North }

Actually I'm not really sure it's a good idea, because it's a fairly easy exercise, which will likely appeal to beginners, and they may get frustrated by opaque type syntax, and the different representations of the robot direction. Wdyt?

[isaacvando]

Looks good! I agree that this could be a good place to use opaque types, but I think it is a good idea to avoid them to keep things simple for beginners like you suggest 👍

[ageron]

Thanks Isaac 👍