1. Slide 1

2. Slide 2 Administrivia Nate's office hours are Wed, 2-4, in 329 Soda! TA Clint will be handing out a paper survey in class sometime this week. Interviews starting next week, from ex-TA Paul Hale –These can be a great place to ask questions This week, the BIG PROJECT is introduced

3. Slide 3 Midterm #2 Any questions?

4. Slide 4 The Big Project Three possible projects: –Database –Blocks World –Yukon You can work in partnerships You will have three weeks to work on this (it is due on the last lab) Worth 10% of you final grade

5. Slide 5 Project Check-offs There are 3 checkoffs You need to do them on time in order to get credit for the project 1.Tell your TA which project you will do and who you will do it with 2.Show your TA that you have accomplished something. S/he will comment. 3.Show that you have most of the work done: your TA will run your code.

6. Slide 6 April 11Midterm #2 (during lecture) Extending sentences, words to lists (in lab) April 18Finish advanced list processing (recursion) Start on the big project CHECKOFF #1 – Thur/Fri April 25Big Project CHECKOFF #2 – Thur/Fri May 2Finish up the Project CHECKOFF #3 – Tue/Wed Project Due on Thur/Fri May 9Review session instead of lecture?

7. Slide 7 Only two more lectures (after this one)… What would you like to do? –Hear about the CS major, and other courses… –Do exam-type problems… –Review… On May 9 th, we could hold a final lecture, or a review session, or nothing…

8. Slide 8 Lets see the projects in action

9. Slide 9 Programming Style Why does it matter –Bad style gets worse in large programs –Program maintenance: 6 months later, will you know what your code does? –Code “literacy”: sharing code Remember, programming style will be considered in your project grade

10. Slide 10 What issues of style matter? Don’t nest conditional statements Keep procedures small ! Good names for procedures and parameters Proper use of global variables Adequate comments –Above and within procedures Put tests cases in a comment block Indent to aid program comprehension Data abstraction –E.g. Don't do (bf (car '((a b) (c d)))

11. Slide 11 Of course, other issues matter Reading specifications carefully Error checking inputs (especially in the database project) Adequate testing Code reuse (again, with the database)

12. Slide 12 Working in partnerships Won't be faster, necessarily –While you are less likely to get stuck, there will be a lot of communication necessary The main strength will be with testing –i.e., two sets of eyes… Remember, only one grade is given… Any other ideas?

13. Slide 13 Functional Programming In CS3, we have focused on programming without side-effects. –All that can matter with a procedure is what it returns –In other languages, you typically: Perform several actions in a sequence Set the value of a variable – and it stays that way –All of this is possible in Scheme.

14. Slide 14 Printing, and sequencing With Blocks World and Yukon you will need to display information. –Simply Scheme chapter 20 is nice summary. –And, all the projects have either file input /output routines that you don't need to "understand", as well as user input routines.

15. Slide 15 Data structures The format of data used in these projects in a central feature –A "data structure" (abstract data type) is a specification of that format. Here, generally, lists of lists (of lists). –Accessors and constructor allow for modularity: letting parts of a program work independently from other parts.

16. Slide 16 Strings versus words One useful data structure is a string –Strings are surrounded by double quotes when printed. –Strings are a native type in Scheme. In CS3, you used words (sometimes sentences) to present names and other output to the user. –In the real world, strings are used.