CS538: Spring 2008

Assignment#1: Scheme

Handin procedure

  1. Your handin folder is in ~cs538-1/public/handin/proj1/login where login is your login name.

  2. Put your solutions in a SEPARATE FILE for each sub-part: 1a, 1b, 2a, 2b, 2c, 2d, 3, 4a, 4b, 5a, 5b, 5c. You can also include a file called README with any notes about your submission, especially analysis of the timing results for part 4b.

  3. Make each file SELF-CONTAINED. Don't load code used in another question (e.g., loading file 2a in the solution for 3b), and don't assume that your code will execute in the handin folder. To achieve this, you may need to make copies of code that is common to multiple sub-parts of the same question.

  4. Each file should make available (at least) the Scheme functions required by the question. Here's the complete list of functions that need to be present in each file. Note that you can have more functions defined, this are just the minimum definitions required in each file:
  5. Your submission must work correctly with DrScheme v208 installed in the linux CS labs and available from the command prompt by typing drscheme (full path is /s/std/bin/drscheme) with the Textual (MzScheme, includes R5RS) language option. The language option is set the first time DrScheme is run, but can be changed at a later time by opening the Language menu and selecting the Choose Language menu item. When prompted to select a language, open the PLT bullet under the Professional Languages section, and select the Textual (MzScheme, includes R5RS) option. You are free to work on your own with another version of DrScheme which you might have downloaded and installed at home (see drscheme.org) but before submission, you must make sure your code runs with our version of DrScheme. You can minimize problems by making sure you set the Language to PLT/Textual MzScheme, includes R5RS. if you use DrScheme library functions, please make sure that these library functions are also available in DrScheme v208 installed here in CS.

  6. Your code will be tested for correctness using automatic scripts and a test suite. So please make sure that the code you submit does not generate extraneous output by calling the display or write or other Scheme output functions. Each of the functions listed in bullet 4 above should silently return values as required by the question. Also, please make sure that your files are free of any top-level tests or timings that you may have used during development.

  7. You can assume that your functions will always be passed valid input, so you do not need to check, for example, that the input argument is a list or a number and so on unless the problem writeup states otherwise. But your functions should be able to correctly handle all valid input, including boundary conditions such as empty lists.

  8. Your handins will be picked up by automatic scripts on the midnight of the due date (March 28), and then again on the midnights of each of the 7 allowed later days (Mar 29-Apr 4). Any files found in a handin folder by our scripts on these 7 days will be deemed to be part of a submission, and that handin folder will be made unwritable immediately. So if you plan to submit late, make sure that your handin directory is empty on the earlier submission days. You can also email the TA to let him know that you are submitting late.

Grading criteria

The first and foremost criteria for grading is correctness. Your programs should execute without errors and produce the correct output with our test suite. Points are awarded for each test input successfully handled by your code.

You can use any algorithms or Scheme functions to produce the correct output, you are not restricted to following the path set by the questions. But you must follow the question when it comes to mandatory requirements, such as using continuations to exit early in Q.5(c) or lazy evaluation in Q.4 or not simply generating all subsets in Q.1(b).

No extra points for the most elegant programs but you are encouraged to write in a functional style, making best use of Scheme's natural abstractions: lists, recursion, higher-order  functions, continuations, and so on. These will invariably reward you with compact, natural-looking code which is easy to read and understand. See the lecture notes and look online for Scheme programs to get a flavor of Scheme programming.  

We will penalize programs that are excessively kludgy and hard to read or understand. Don't try to write C++ or Java in Scheme. In particular, the excessive use of the update operator set! (and its relatives) is frowned upon and will be penalized.

Partial credit will be given for programs that seem to be on the right track.

Scheme Tips

First of all, check out the 538 Scheme page for information on DrScheme and how to use it in the CS Department.

Note that we have DrScheme v208 installed in the CS linux labs available off of the command prompt by typing drscheme. If you are using older versions of DrScheme, then be aware of things that work differently in the older versions:
- Written by Akash Lal, updated by Kevin Roundy, Mark Goadrich, Charles Fischer