Labyrinth & Formats

CS 4500 Assignment B

Due Tuesday, September 24, midnight

Submission You must deliver your artifacts in a directory called B in your repository (master branch, see note below):

  1. For task 1, – the specification document.

  2. For task 2, an executable called B, together with a file called format only containing one of these 3 strings json, xml, or sexp.

All auxiliary files must be put into a sub-directory called Other.

Note: When this assignment is released you will not have the details for your repository yet. These will be provided shortly after releasing this assignment.

Task 1

Your company has hired a group of stellar programmers. Your manager has put you in charge of writing a specification for the interface for a module, dubbed Labyrinth, which these stellar programmers will implement in your favorite language and ship back real soon.

As the name suggests, the high-level purpose of the desired module is to provide the services of a basic labyrinth. For our purposes a labyrinth is a connectivity specification for nodes in a simple graph, and a simple graph contains at most one edge between any pair of nodes. The desired software must support these operations:

  1. the creation of a plain labyrinth with named nodes;
  2. the addition of a colored token to a node;
  3. the query whether some colored token can reach some named graph node.

Formulate your specification in a mix of English and technical terms appropriate for your chosen language. For example, in Java you would use the term package and you might use types while a Python programmer would speak of modules and use informal data definitions.

Write the specification using the Markdown format. When printed, it must fit on a single page. Specify the precise language (name, version) in which you expect the product to be written in.

The goal of Task 1 is to get a glimpse of the tasks that team leaders perform in software companies. This specification is quite small so that a single page should easily suffice to give precise instructions to developers.

Task 2

In this task you’ll explore data exchange formats in your chosen language. We gave you a choice of supporting JSON, XML, or s-expressions. We recommend using JSON, but we’ll give you the flexibility to choose a different format.

Develop a program that reads a series of well-formed XML/JSON/s-exp values from standard input (STDIN). Values are restricted to the following format:

  1. strings
  2. arrays, where the first element is a string
  3. objects, where the object has a key “this” and whose value is a string

No other format of input should be accepted.

In addition to reading from STDIN, your program should accept two command line options: -up or -down. Based on the argument, the program will sort the values in ascending (-up) or descending (-down) order, according to the string designated string parts (i.e., the string itself, the first element of an array, or the “this” component of an object.

Example Input

Here are example inputs:

  1. JSON
        ["b", 1, 2, 3]

        {"this" : "c",

             "other" : 0}
  1. XML
        <?xml version="1.0" encoding="UTF-8" ?>

        <?xml version="1.0" encoding="UTF-8" ?>

        <?xml version="1.0" encoding="UTF-8" ?>
  1. S-expressions
        ("b" 1 2 3)


        ((this "c")
         (other 0))

Example Output

If invoked with -up the program should output something like this for input in JSON.


        ["b", 1, 2, 3]
        {"this" : "c", "other" : 0}

Similarly for XML and s-expressions. The output should be in the same format as the input. Specify which format your program is using (as json, xml, or sexp) in a text file called format supplied with your executable.

The goal of Task 2 is to figure out:

  1. how your language processes command line arguments,
  2. whether it has a good library for reading and writing structured data formats, and
  3. how to deploy programs that run on Linux in your chosen language. See sources like this one for details.