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Homework extension

Thu Mar 27 8:29:00 EST 2014 The SkipList homework is a bit confusing and some students are having trouble completing it. So I’m extending the homwork until Monday evening: it will be due by 6:00pm before lab.

As a hint: each Element represents one column of the diagram, which means each Element contains a single key (in the diagram, a yellow box with a number in it), a single value (not shown in the diagram, unfortunately), and a list of links to subsequent SkipListNodes (the rightward arrows). Getting the type of links right is tricky. You may want to represent the links as pairs of an Element and a level number, rather than as a Deque Node or some such (it is rather subtle to get the exact type parameter correct). Representing links this way makes it possible to get the linked Element easily, on which you can then use getValue, getKey, etc., and especially getNext.

Final project ideas

Mon Mar 24 5:20:00 EST 2014 Your final project is to implement one of the following two games in Java using the world library. Each project will have a minimal set of required features, and then a set of “whistles” (easier, smaller extensions) and “bells” (harder, larger extensions) that you can implement to embellish your project. NOTE: I may add a few more required features over the next couple of days. Keep an eye out for changes. If you have additional ideas for a whistle or bell, come talk to me about it so we can accurately judge how much work is likely needed.

No homework for Thursday this week

Tue Mar 18 21:08:12 EST 2014 Study for the exam on Monday. A new assignment will go out Thursday and be due next Thursday.

Final Project Partnerships

Thu Mar 13, 9:30:00 EST 2014

Final Homework Partnerships

Note on Homework 8

Thu Mar 6 10:03:00 EST 2014 It is entirely possible to solve this homework without needing to use type-casts or modifying the IList interface with methods like asConsList or asQuickList. As a hint: my example solution uses three constructors for QuickLists:

class QuickList<T> implements IList<T> {

// Creates an empty QuickList

QuickList();

// Creates a single-element QuickList

QuickList(T t);

// Creates a QuickList with the given forest of elements already set up

// NOTE: Clients should never get to use this!

QuickList(IList<Tree<T>> forest);

}

My solution then has roughly one visitor for each operation you need to implement (reverse, append, get, first and rest), for example:

class ReverseVisitor<T> implements IListVisitor<T, IList<T>> { ... }

To implement cons, though, you have to be a bit clever. Because the algorithm behaves differently when the QuickList’s forest is empty, has one element, or has multiple elements, you need two visitors:

class ForestVisitor<T> implements IListVisitor<Tree<T>, IList<Tree<T>>> {

T elemToConsOntoFront;

ForestVisitor(T t) { this.elemToConsOntoFront = t; }

...

}

class ForestVisitor2<T> implements IListVisitor<Tree<T>, IList<Tree<T>>> {

T elemToConsOntoFront;

Tree<T> firstTreeInForest;

...

}

Note on Homework 7

Tue Feb 25 10:44:00 EST 2014

For this assignment, don’t try to use generic IList<T> types to define schedules. Define an ISchedule and classes NoEvent and ConsEvent accordingly. You’ll need to use type-casts otherwise, which is not a good idea. You may be able to use IList<T> successfully in the string-dictionaries problem, and you won’t need any generics (or lists) at all in the tries problem.

Assignment 7 out

Fri Feb 21 10:53:15 EST 2014

The next assignment is out. It’s long – get started early!

Practice exam questions now available

First exam: In class, Monday 2/10

Tue Feb 4 09:47:40 EST 2014

Chris will not have office hours today, but will hold them instead on Friday, 5–7pm.

Initial Partnerships

Follow the bouncing ball

Thurs Jan 9 15:45:00 EST 2014 In class today we started an example of animating a bouncing ball in an object-oriented big-bang program. Part of the challenge was simply to model the bouncing of the ball in a way that was natural for the computation. But the follow-on challenge is to reuse that code to implement multiple bouncing balls – without having to change the implementation of the ball’s class(es). I’ll post the solution to this on Monday, but for now I’ll describe the problem in more detail:

Define a class (or classes) to represent a bouncing ball of radius 10, of some color, moving at some initial velocity and at some initial position. Assume that gravity accelerates the ball at 1 pixel / second / second. You should be able to pass such a ball object into big-bang and have it animate. Next, define a world% class that represents a list of balls. Running this world% should animate all the balls simultaneously. In particular, can you implement world%’s on-tick and to-draw methods without calling any drawing functions?

Correction to HW1

Wed Jan 8 10:40:03 EST 2014 We do not yet have GitHub set up. For now, for homework 1, just email Chris your completed assignment.

We also have not assigned programming partners yet. For homework 1, you can continue to work with the lab partner you worked with on Monday. Make sure that your submitted assignment includes both your names, so we know who worked on what.

Welcome to CS2510H

Fri Jan 4 16:06:59 EST 2013

We hope you’ll have fun.