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Assignment 1: Venusians Due Friday January 28, 10:00pm EST

Change Log

  • 1/13/22: Initial Release
  • 1/16/22: Add pointer to textbooks page - JB
  • 1/18/22: Specify return types on Venusian class, and clarify that Venusian names are case-sensitive - JB
  • 1/19/22: Update spec for Venusian to clarify captialization of the member method getVsn, to match the test included in the handout. -JB
  • 1/19/22: Added a “Getting Started” section to help set up the development environment for the starter code locally. -SR
  • 1/20/22: Clarify that unique ID’s need only be unique for a single execution of your program and need not be globally unique IDs. -JB

Objectives of this Assignment

The objectives for this first assignment are to:

  • get you familiar with the basics of Typescript and the VSC/npm ecosystem.
  • have you re-acquaint yourself with the basics of object-oriented programming, such as classes and objects.
  • learn to write new code in TypeScript.

Your assignment will be graded following the rubric embedded in this document. Based on past experiences, we project that this assignment could take you up to 14 hours (depending on your prior preparation). We encourage you to start early so that you can post questions on Piazza, make the most use of our TAs’ tutorials, and attend office hours as necessary in order to ensure that you can reach Satisfactory marks across the board.

This is an individual assignment.

Please post any questions about this assignment on Piazza. We have many sections of this class, and we want to make sure that we respond to your questions the same way, regardless of which section you are in.

Problem Statement

Mars is being invaded by Venusians. Here’s a description of the Venusian fleet:

  1. Each ship has a serial number, a crew, which is a list of Venusians, and a possibly-empty set of daughter ships, each of which is a ship.

  2. Each Venusian has a name, which is a string, and a VSN (Venusian Security Number), which is a number.

  3. When we say “fleet”, we mean a list of ships and their daughters, their daughters’ daughters, etc.

  4. When we say the “fleet of a ship”, we mean the fleet consisting of its daughters.

EXAMPLE: if ship 1 has daughters ship 11 and ship 12, and ship 11 has daughters 111 and 112, and ship 112 has daughters 1121 and 1122, and none of these ships has any other daughters, then the fleet of ship 1 consists of 1, 11, 12, 111, 112, 1121, and 1122

Your task is to define TypeScript class Venusian and Ship as follows:

  • The class Venusian has a contructor new Venusian(name:string) that returns a Venusian with the given name and a unique VSN. By “unique”, we mean that while your program is running, it must never re-use a VSN. It is OK for your program to re-use the same VSNs if you stop the program and run it again (it need not be a “globally unique” identifier). Venusian names are case-senstive. The class Venusian has the following public methods:

    • getName():string returns the name of the Venusian.
    • getVsn():number returns the VSN of the given Venusian
  • The class Ship has a constructor new Ship(crew:Venusian[], daughters:Ship[]) that returns a ship with the given crew, the given daughters, and a unique serial number (similar to VSNs, the serial number need not be globally unique). The class Ship has the following public methods:

    • getCrew():Venusian[] returns the crew of the ship.
    • getDaughters():Ship[] returns the daughters of the ship.
    • getSerialNumber():number returns the serial number of the ship
    • hasWaldo():boolean returns true iff the ship has one or more crew members named Waldo.
    • totalWaldos():number returns the number of Venusians named “Waldo” that are in the ship or its fleet. Venusians can be in two places at once, so if two Waldos have same VSN, you should count them twice.
    • removeWaldos():void removes any Venusians named “Waldo” from the crew of the ship.
    • removeDeepWaldos():void removes any Venusians named Waldo from the crews of the given ship and its fleet.
    • fleetHasDuplicates():boolean It has come to the attention of the Venusian fleet command that some shipbuilders have been cheating by putting multiple ships with the same serial number in the fleets of their ships. Given a ship, determines whether there are any duplicates among the ship and its fleet. The duplicates may occur anywhere in the ship and its fleet.`

EXAMPLE: in the example above, there are no duplicates. If ship 12 were added to the daughters of ship 111, that would be a duplicate, and applying this function to ship 1 would return true.

Starter Code and Details

We will supply you with starter code in

Getting Started

  1. Download and unpack in a fresh directory. You should have a directory hw1-handout containing package.json, src/ and a bunch of other files.
  2. Open hw1-handout in VSCode.
  3. Open up the VSCode terminal with ctrl + ~. Alternatively, you can also open a seperate terminal/cmd. Please make sure the shell is in the same folder as your package.json.
  4. Fetch all the necessary dependancies by running npm install. You may not install additional third-party libraries to use in your code beyond what is included in the handout - we will grade your code using the package.json distributed in the handout.
  5. The package also includes some basic sanity tests, which you can run by saying npm test.

To help you set up a local development environment for this class, we’ve prepared a tutorial for setting up a development environment with NodeJS, VSCode and TypeScript. Additionally, An Absolute Beginner’s Guide to Using npm can help you in getting acquainted with npm. As a reference for getting started with TypeScript, we suggest the book “Programming TypeScript” by Boris Cherny. You can read this and many other tech books for free via Northeastern’s Libraries - follow the instructions on the course textbooks page.


Your code will be evaluated by automated testing in Gradescope. It will be judged for style using a linter with parameters set in the starter code that we will supply you. Your code must have no linter errors or warnings in order for it to receive any grade. Please note that you can check for linter issues before submitting by running npm run lint; many formatting issues can also be automatically fixed by running npm run format.

If your code has no linter errors or warnings, then for each of the 10 methods listed above, you will receive a numeric score of:

  • 2 (Satisfactory)
  • 1 (Meets minimum expecations)
  • 0 (Not passing)

We have provided between one and three tests on Gradescope to check each of the ten functions that you have been asked to implement. For each function, the requirements for each of these grades are:


  • Have no errors or warnings reported by the linter
  • Passes all of the Gradescope tests for this function

Meets minimum expectations

  • Have no errors or warnings reported by the linter
  • Fails no more than one of the Gradescope tests for this function (while also passing at least one)

Not Passing

  • Does not meet the minimum expectations.

When we say “no errors reported by the linter”, we mean the following:

  • Have no style errors (may have warnings) as reported by npm run-script lint

  • Have no @ts-ignore or eslint-disable annotations in the code that you write.

Submission Instructions

Submit your assignment in GradeScope. The easiest way to get into GradeScope the first time is to first sign into Canvas and then click the link on our course for “GradeScope”. You should then also have the option to create an account on GradeScope (if you don’t already have one) so that you can log in to GradeScope directly. Please contact the instructors immediately if you have difficulty accessing the course on GradeScope.

Submit your solution to Gradescope in the form of exactly two files, Venusian.ts and Ship.ts. Before submitting, be sure your code passes the sanity tests included in the starter package. GradeScope will provide you with feedback on your submission, providing a numeric score between 0 and 20.

You will be able to view the complete output from running the tests and linter on GradeScope. If you have any doubts about the autograder, please contact the course staff immediately. In particular, if you are not able to reproduce and debug test or linter failures on your local machine, please ask the TAs for assistance: otherwise you’ll waste an immense amount of time waiting for the autograder to complete, when you could get the same feedback in seconds running the tests + linter locally.

You may submit solutions as many times as you want; only the last submission before the deadline will be counted.

© 2022 Jonathan Bell, Adeel Bhutta, Ferdinand Vesely and Mitch Wand. Released under the CC BY-SA license