CSC 160
Homework 3

Assigned Sept 27, due Oct 4 Oct 20

Pair Programming

You are encouraged to do this assignment in a two-student team, following the principles of Pair Programming. This does not mean "you do these problems and I'll do those"; it means both students work together, looking over one another's shoulders, to complete all the problems. Turn in one copy with both names on it. I recommend that you choose a different partner for the next homework assignment, so if you don't get along with this partner, remember it's only for a week :-)


This is a lot of problems; do a few every day in order to finish them on time. In addition, we'll do some of them in class. Problems marked "for practice" don't need to be turned in, but I recommend doing them to your own satisfaction before doing the next "real" problem.

What to turn in and how

For problem 6.8.2, I recommend printing out the relevant Scheme code on paper, drawing on the paper, and turning in the paper. (This can be done on the computer, but I think it's more hassle than it's worth.)

You may turn in problem 7.6.2 on paper or by e-mail.

For the programming problems, I want to see all the steps of the recipe, except that in the course of writing a function body, you normally replace the "..." that was in the function skeleton. I recommend putting all of the programming problems in one big Definitions pane, because some of them depend on others.

It's difficult for me to grade your testing of these functions, but be assured that I will test them, and if they don't work, it'll hurt your grade, so it's to your advantage to test them before turning them in.

Send me an e-mail, attaching the file containing your saved Definitions pane. (Make sure to save it, then test it, then e-mail it to me, or I may end up grading an out-of-date version.) Make sure to put your name in the Subject line!

If there's a particular function that you can't get working, turn in as many steps of the recipe as you've managed to do, commented out (so they don't mess up the other functions).

Also turn in a log of how many errors of different kinds you encountered in the assignment, with brief comments describing each one ("mismatched parentheses" is self-explanatory, but more complex errors might need more description). Note that "errors" means not only error messages from DrScheme, but also wrong answers. You may do this using the PSP forms, or simply by keeping track in a text file or on paper and turning it in.

Grading standards

In order to get you feedback quickly, I won't actually grade all of these problems; the rest should be considered practice.

Error log:       25 points
(I'm not grading on how many or how few errors you encountered, only on whether you recorded them correctly.)

Box-diagram exercise 6.8.2:     10 points
Contract exercise 7.6.2:     5 points each contract

Programming exercises:

The table below has columns for each step in the design recipe, and a row for each function that I decide to grade. You won't turn in a separate skeleton, inventory, and body, but rather write a skeleton and then add inventory and body to turn it into a complete definition. However, if you don't get the definition working, you'll still get partial credit for a correct contract, skeleton, and/or inventory.

Function Contract Examples Skeleton Inventory Body
whatever /5 /5 /5 /5 /15

General skills:

Following directions /10
Writing contracts from word problems /10
Choosing examples /10
Choosing names, indentation, white space... /10
Coding /10
Code re-use and function composition /10

Total:         /???

Last modified: Mon Sep 26 19:41:14 EDT 2011
Stephen Bloch /