CSC153, Class 31: Even More Intro Java
  Lab, That Is

Overview:
* Preparation
* Lab

Notes:
* Graphical program development system?  No way!
* Reminder: Extra credit for attending convo
* Questions on exam 2?
  Q: May we assume that the dot can only appear before
    the last thing?
  A: Certainly
  Q: Do we have to do syntax checking?
  A: "Precondition: The string contains syntactically-correct
      Scheme"
  Q: How do I convert a string to a symbol?
  A: string->symbol

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Preparation

Add to .bashrc

export PATH=/usr/java/j2sdk1.4.1_01/bin:$PATH

LAB

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Reflection:

* Some aspects of the Java environment are a pain in the neck
  + Figuring out the CLASSPATH
  + Refreshing applets
* How is computer programming like a video game?
  Level one: Can I get it to compile?
  Level two: Can I get it to execute without crashing?
  Level three: Can I get it to give at least one correct
    answer?
  Level four: Can I get it to usually give correct answers?
  Level five: Can I get it to always give correct answers?

both (like and)
either (like or)

(define even-number? (both even? number?))

(define list?  
  (either null? (and pair? (compose list? cdr))))

(define x (+ x 1))

(define list?
  (lambda (val)
    (or (null? val)
        (and (pair? val)
             (list? (cdr val))))))