Rover

Introduction

This is a simple terrain walker in the form of a rover on Mars. It comes in many formats the earliest being Logo. It has a variation where there is a a map with terrain markers and parts you cannot walk on. Since there was no functional language options on the list and due to Ruby's morphability, I decided to write it in a pure Functional Ruby format. This problem can easily be modeled in an OO methodoly but thought it would be more fun in a functional specification.

My Environment is:

• Ruby 2.2.1p85 on
• Ubuntu 16.04 LTS

Operational

To run the program simply do: ruby rover.rb PATH_TO_INSTRUCTION_SET OPTIONS:

• -l Verbose, the default for this is true

The program will respond with and error state or the final location on success. It will be verbose by default. This can be disabled if you just want to run through the program as fast as possible. If you want to switch of verbosity simply pass the -l option false. This will make the program run an non pausing speed and just show the result ruby rover.rb PATH_TO_INSTRUCTION_SET -l=false

Design

The grid start at 1,1 it the bottom left conner. Below is a 3x3 and the Rover at positon 1 2 E

    N
  1 2 3 
 3
W2>    E
 1
    S

Psuedo

• The Rover checks if a file is received with instructions it retrieves
• It then send the data received for validation. This insures that all logic after this acts on contractually sound data
• If that passes it sends the instruction set to start the Engine
• The Engine configures and starts at the initial location on the Terrain
• It then begins to excute its instructions an drive the set one command at a time

Since you only need to know where you end up there is no need to move in a datastructure, like a 2d array. One can just move across the rows and columns depending on your direction. Also the direction is done with switching so you dont have to have logic that knows what comes after a certain directional point. You can switch directions index up or down depending on if you need to go Forward, Backward, Left or Right. In general terms East and West moves forward and backward in columns, and North and South forward and backwars in rows.

Fails safe

The rover will never go outside of it defined zone, if commands want to go over a boundary the rover will not move beyond the boundary and will ignore that command. It then tries the next command and either move back or along the boundary. If you keep making commands beyond the boundary direcion, it will most probably just get stuck in a corner eventaully and never go beyond that point. This is and ultimate fail safe even if you keep sending commands to it.

Testing

Each exposed function has a has a unit test in the tests folder. Most of the modules where coded in a TDD fashion to make it fun. But the order of this is immeterial, as long as all the test run before the coding is done. To run the tests simply execute this command, I run this on Ubuntu: find tests/ -name 'test_*' | xargs -n1 -I{} ruby -Itest {}

I have also added a functional test test_instructions.bla. The output of this should be [4, 4] S, after driving up down each colomn. The original problem is also in the file original_instructions.bla. This should give the output [3, 3] S