Due: Thursday, January 28th at 9pm

Submission: The submission process is as follows.

  1. At the top-level of your Khoury GitHub repository, which we created for you, create a directory A2 with the following:

    1. the file traveller.md – the artifact from Task 1
    2. the directory src/ containing the source code for the program a2 from Task 2

  2. Create a new release on GitHub, named a2 and add a ZIP file a2-exec.zip as the “binary” containing the a2 executable and any auxiliary files required by the executable. Details on how to do that are here.

  3. Download the Source code (zip) from the release and submit it via Handins.

Task 1

Your company wants hire a consultancy to develop a module. You were put in charge of writing a specification for the interface for a module, dubbed Traveller. This specification will be implemented by the newly hired programmers in your chosen language and ship back real soon.

The high-level purpose of the desired module is to provide the services of a route planner through a network of towns for a role-playing game. For our purposes, a town network is a simple graph specification together with a placement of in-game characters.

The module must support these operations:

  1. the creation of a town network with named nodes;

  2. the placement of a named character in a town; and

  3. a query whether a specified character can reach a designated town without running into any other characters.

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. You might want to revise material on data definitions from Fundies I.

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

Pedagogy

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 suffice to give precise instructions to developers.

Task 2

The company-wide poll on a data interchange format showed an overwhelming support for JSON Now it is your turn to explore the JSON capabilities of your chosen language.

Write a program, a2, that reads a series of well-formed JSON strings from STDIN. In addition to being well-formed JSON, the values are also valid elements of this set:

A NumJSON is one of the following kinds of well-formed JSON values:

  • A Number or a String
  • An Array of NumJSON
  • An Object containing at least the key "payload" whose value is a NumJSON. Other keys might contains arbitrary NumJSON values, but these are irrelevant and to be ignored.

No other well-formed JSON values are valid NumJSONs.

The program should also take a single command line argument, which is either --sum or --product. Once STDIN is closed, the program should, for each of the given NumJSON values, compute a sum or a product (depending on the given argument) of all numeric values contained in the NumJSON. The result for a String value should be the unit for the respective operation (0 for --sum, 1 for --product). In other words, they are ignored and don’t change the result. For Objects, only consider the "payload" value. The output should be a JSON array of objects with the fields "object", containing the original NumJSON value, and "total", containing the total computed for that object.

Here is a sample single input:

12        [2, "foo", 
4]  { "name" : "SwDev", "payload" : 
  [12, 33]     , 
        "other" : { "payload" : [ 4, 7 ] } }

If invoked as ./a2 --sum, the output should be:

[ { "object" : 12, "total" : 12 },
  { "object" : [2, "foo", 4], "total" : 6 },
  { "object" : { "name" : "SwDev", 
                 "payload" : [12, 33], 
                 "other" : { "payload" : [4, 7] } }, 
    "total" : 45 } ]

If invoked as ./a2 --product, the output should be:

[ { "object" : 12, "total" : 12 },
  { "object" : [2, "foo", 4], "total" : 8 },
  { "object" : { "name" : "SwDev", 
                 "payload" : [12, 33], 
                 "other" : { "payload" : [4, 7] } }, 
    "total" : 396 } ]

Note that whitespace is insignificant, both on input and on output.

Pedagogy

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 JSON, and

  3. how to deploy programs runnable in LINUX in your chosen language. See sources like this one for details.