CSC151.01 2014F, Class 05: Drawings as Values
=============================================

_Overview_

* Preliminaries.
    * Admin.
    * Upcoming work.
    * Extra credit.
    * Questions on `mod`
    * Questions on HW2.
    * Quiz!
* Lab.

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

### Admin

* New lab partners.
    * Take a playing card.
    * Sit at the computer on the playing card.
    * Introduce yourself to your partner when he/she/zi sits down.
* No attendance today.
* You can view [notes from yesterday's review session](../eboards/extra.01.html)
* Our final is scheduled for Friday of finals week.  It is optional.
  I am happy to work out other times with you individually, if that time
  does not work.
* I have flash drives with virtual Linux computers that you can run on
  your Mac or MS Windows machine, along with instructions.  Feel free
  to take a flash drive, but please bring them back after uyou get it
  installed.
* Since it's a weekend, a few reminders.
    * Decide what *you* want and what *you* feel comfortable with.
    * And please, if you drink, please drink responsibly.

### Upcoming Work

* Lab writeup for today (due Monday): Exercise 4, parts a, c, and f.  
  See link on schedule or list of labs for link to submit it.
* [HW 2](../assignments/assignment.02.html) is due Tuesday.
* Reading for Monday: 
    * [Writing Your Own Procedures](../readings/procedures-reading.html)

### Extra Credit Opportunities

* Note: Please send a short (one paragraph) reflection on any extra credit
  activity you attend.  And reflect, don't summarize.

#### Academic

* Awesome show at the Faulconer gallery.
* Convo next Wednesday at noon.  "Limiting Armed Drone Proliferation" by 
  Micah Zenko, the Douglas Dillon fellow in the Center for Preventive
  Action at the Council on Foreign Relations and vice chair of the World
  Economic Forum Global Agenda Council on Terrorism.
    * Sam's comments on the value of convo
* Any other event in the Rosenfield Drones program.
* CS Extra, Thursday, September 11: Ajuna Kyaruzi '17 on being a SysAdmin

#### Peer Support

* Football Games (???)
* Women's Volleyball home matches (???)
* Men's Tennis home matches  (???)
* Women's Tennis home matches (October 11)
* Anna Christie, Oct. 9-12 (SB plays Marthy)

### Question on `mod`

* "Does the choice of `mod` or `remainder` affect more than the sign?`
* Consider 7 and 4.

	> (mod 7 4)
	3
	> (mod -7 4)
	1
	> (mod 7 -4)
	-1
	> (mod -7 -4)
	-3
	> (remainder 7 4)
	3
	> (remainder -7 4)
	-3
	> (remainder 7 -4)
	3
	> (remainder -7 -4)
	-3

* Let's divide -7 by 4.
    * -7 is 4*-1 with a remainder of -3
    * We can also think about -7 as being 4*-2 with a remainder of 1
* If we use both `mod` and `remainder` for cycles, why would we use one over
  the other?
    * With a positive divisor/modulus, `mod` only cycles through non-negative
      numbers, and the cycles go in the same direction
    * With a positive divisor/modulus, `remainder` cycles one way for
      positive dividends and the other for negative dividends, and the
      signs of the values in the two cycles are opposite.
    * For these reasons, we tend to use `mod` to cycle.

### Questions on HW2

* Why is vertical shifting upside-down?
    * Silly graphics pioneers decided that numbers increase downward
    * Possibly because of printing.

### Quiz

10 minutes.  If you finish early, start setting up for the lab (but wait
for your partner to do the real work).  Read the reading again if you have
nothing else to do.

Lab
---

* Since we started this lab late, we will continue it for the first
  fifteen or so minutes on Monday (and the lab will be due Wednesday).
* And since you were having trouble,