CSC151.01 2014F, Class 09: Side Effects: Images, Output, and More
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_Overview_

* Preliminaries.
    * Admin.
    * Upcoming Work.
    * Extra Credit.
    * Questions.
* Quick comments on today's topics.
* Quiz.
* Lab.

Preliminaries
-------------

### Admin

* Maintain lab partners from yesterday.
* Structure: Preliminaries, Quick comments, Quiz, Lab.
* Quick observations from epilogues
    * Part D was clearly the hardest part.  I hope it was useful.
    * Epilogues should be individual.  Don't do them with your partner.
    * I generally expect homework assignments to take 2-4 hours.
    * Mostly positive group experiences, but some scheduling difficulties.
    * A bit of frustration on lack of textbook and availability of help.
    * Sunday mentor hours?
* Favorite quote: "It seems like every time I think something is going
  to be easy, it's complex, and every time I think something is going to
  be complex, it's easy."
* Since students don't always know what faculty do ... about 90 of us
  are getting together at lunch today to discuss the future of liberal
  arts education, using *Remaking College* as the basis of our discussions.
* It's weekend.  Please reflect in advance on what decisions will be
  appropriate for you.  And if you choose to drink, please drink 
  responsibly.

### Upcoming Work

* Lab writeup (due Monday): Exercise 3a (annotated versions of each of the
  drawing procedures).  <http://bit.ly/151-2014F-w09>
* Reading for Monday:
    * [Testing Your Procedures](../readings/rackunit-drawings-reading.html)

### Campus Events of Interest

* Rosenfield seminar on Scotland, Monday (noon?)
* Rebecca Hamlin book talk Wednesday at 4:15 pm.

### Extra Credit Opportunities

#### Academic

#### Peer Support

* Football Games 
  (Beloit)
* Women's Volleyball
  (Sat 9/13 @ 2pm and 4pm and Sun 9/14 @ 11am and 1pm in Darby.)
* Men's Tennis 
* Women's Tennis 
  (Away next weekend)
* Anna Christie, Oct. 9-12 (SB plays Marthy)

### Questions

* No questions submitted online.
* Nothing in the prologue suggests confusion on the homework.

Quick Introduction to Side Effects
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* Two main points in today's readings
    * Changing perspective - Procedure that do modify their parameters
      (or the world around them).  Order matters, a lot!
    * Is we can hack at Scheme to better understand what it's doing
      (annotate)

Quiz
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* It's okay if you found it difficult.  It can be a learning experience
  for both of us.

Lab
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* DrRacket distinguishes between a string that names a file that
  contains an image, and the image that you get from `image-load`.

        > (image-load "/home/rebelsky/Desktop/me.jpg")
        4
        > (define me (image-load "/home/rebelsky/Desktop/me.jpg"))

* If you show an image and then close the last window that shows the
  image, Gimp no longer believes it's an image, and so DrRacket will
  complain if you do anything else with it.
* The writeup is 3a.