Instructions

Manage robot factory settings.

When a robot comes off the factory floor, it has no name.

The first time you turn on a robot, a random name is generated in the format of two uppercase letters followed by three digits, such as RX837 or BC811.

Every once in a while we need to reset a robot to its factory settings, which means that its name gets wiped. The next time you ask, that robot will respond with a new random name.

The names must be random: they should not follow a predictable sequence. Using random names means a risk of collisions. Your solution must ensure that every existing robot has a unique name.

To complete this exercise, you need to create the data type Robot, as a mutable variable, and the data type RunState. You also need to implement the following functions:

initialState
mkRobot
resetName
robotName

You will find a dummy data declaration and type signatures already in place, but it is up to you to define the functions and create a meaningful data type, newtype or type synonym. To model state this exercise uses the State monad. More specifically we combine the State monad with the IO monad using the StateT monad transfomers. All tests are run with initialState as the state fed into to evalStateT.