CS200: Notes 14 March 2003

University of Virginia, Department of Computer Science
CS200: Computer Science, Spring 2003

Notes: Friday 14 March 2003

Schedule

Now: Problem Set 5: Wahoo! Auctions
Wednesday, 19 March: Read GEB, Aria with Diverse Variations and Chapter 13. This chapter proves that the halting problem is not decidable, and introduces the Church-Turing Thesis (which we will explore more in Classes 32-36). You will not be assigned to read Chapter XIV, but it goes into more depth on Gödel's proof and it recommended.
Monday, 31 March: Problem Set 8 team requests. For PS8, you will work in teams of 1-6 people (preferably 3 in most cases) to build a dynamic, database-backed web site. If you want to request your own team, you need to decide as a group to be a team, and send me a single request that you cc: to all your potential team members. In order to increase the chances I honor your request, your email should not only list the team members but should give a brief description of the web site you have agreed as a group to build. Students who do not request teams, will be arbitrarily grouped into teams.
(define (make-ocounter)
  ((lambda (count)
     (lambda (message)
       (if (eq? message 'reset)
	   (set! count 0)
	   (if (eq? message 'next) 
	       (set! count (+ 1 count))
	       (if (eq? message 'how-many)
		   count)))))
   0))
(define (make-ocounter)
  (let ((count 0))
    (lambda (message)
      (if (eq? message 'reset) 
	  (set! count 0)
	  (if (eq? message 'next) 
	      (set! count (+ 1 count))
	      (if (eq? message 'how-many)
		  count))))))
What is an object?
How to Smalltalk-ers add 2 + 3?

Why is it useful to package state and procedures together?

Recommended Reading: Howard Rheingold, Tools for Thought, Chapter 11: The Birth of the Fantasy Amplifier.
The best way to predict the future is to invent it. — Alan Kay
If you have an idea, and its not a good idea, take a nap instead of implementing it. — Alan Kay








	CS 200: Computer Science Department of Computer Science University of Virginia Circle Fractal by Ramsey Arnaoot and Qi Wang	cs200-staff@cs.virginia.edu Using these Materials