CSC151 2007S, Class 35: Writing Script-Fu Procedures

Admin:
* Are there questions on the exam?
  * Problem 1
  * Problem 2 "Unriffle"
    * What does "implement" mean?  It means "write the procedure"
      a. Documented
      b. Tested
      c. (define unriffle
           (lambda (lst)
	      ...))
    * Local helpers?
      c. (define unriffle
           (letrec ((fred (lambda (...) ...))
                    (ginger (lambda (...) ...)))
             (lambda (lst)
	        ...)))
  * Problem 3 - in-tree?
    * Can I use member?
      * You may not *call* member? or member
      * You may, however, use member? as a source of ideas
        (Which you need not cite.)
    * Examples for in-tree?
      > (in-tree? 'a null)
      #f
      > (in-tree? list null)
      #f
      > (in-tree? "I hate writing examples" null)
      #f
      > (in-tree? 'a (cons 'a 'b))
      #t
      > (in-tree? 'a (cons 'b 'a))
      #t
      > (in-tree? list (cons 'a "b"))
      #f
      > (in-tree? list (cons car cdr))
      #f
      > (in-tree? "I hate writing examples" (cons "I hate" "writing examples"))
      #f
      > (in-tree? "I hate writing examples" (cons "I hate writing examples" "that are shorter than 200 lines"))
      #t
      > (in-tree? 'a (cons (cons 'b (cons 'c (cons 'a 'x))) (cons 'x 'y)))
      #t
* I've had a request from one student to turn in the exam on Tuesday morning, 
  so I'll be rearranging next week's schedule a bit.
* I've been asked to meet with a department at 11, so I will be 
  unavailable for office hours.

Overview:
* Reflections on the first Script-Fu Lab.
* Writing procedures for Script-Fu.
* Lab.

/Reflection/

* What was your favorite part of yesterday's lab?
  * Seeing the amusing color names
  * "It was wicked fun"
* What was your least favorite part of yesterday's lab?
  * Script-Fu console is "small" - only one line for the code
  * More trouble than its worth to draw something - I can select
    and stroke by hand much faster than I can do in code.
  * Error messages were not incredibly helpful
  * Missing it
* What advantages, if any, are there from being able to write
  Script-Fu commands for GIMP?  (As compared to doing things manually?)
  * "I can't draw a straight line, so it was helpful to have the
     computer do it for me."
  * When you care about precision (e.g., modern or premodern values),
    it's easier
  * Replication is easier
  * Code can provide a clearer explanation, too.
* What advantages are there, if any, for being able to do manual stuff
  in addition to the Script-Fu?
* What else would you like to learn about Script-Fu? 
  * I won't necessarily follow your guidance, but I might.
  * "I'd like to do animation."
    * Yes the GIMP can do some forms of animation.
    * But Sam's not sure how - Other than draw, pause, erase, draw, pause, erase
* What other commands would you like?

/Step One: Procedures/

* To do manyinteresting things, you'll need to write procedure.
* Procedures can combine operations
* Proceduers can parametize operations
  E.g., for a simple animation, a "draw-frame" procedure might take
    the frame number as its parameter
* The GIMP does not provide an easy way to write procedures.
* So we write the procedures in DrScheme and load them into the GIMP