CSC151 2009F, Class 22: Conditionals

Admin:
* Exam 1 returned.  We'll spend a few minutes of class discussing 
  general issues.
* Reading for Tuesday: Building Images by Iterating Over Positions.
* Are there questions on Lab Writeup 4?
* Are there questions on Assignment 5?
* It's a new week, and therefore time for NEW PARTNERS
  * Try to choose someone you have not worked with before

Overview:
* The parts of an algorithm, revisited.
* Choosing between two options with if.
* Making multiple choices with cond.

Notes on the Exam
* In case it wasn't clear, for each of the ten problems on the exam,
  I marked either check (for correct) or the number of points you lost
  on the problem.  In a few cases, I marked the number of points you
  gained on the problem.
* The answer key to the exam was distributed electronically.
  * Read it
  * Don't share it with others
* If you invoked the "There's more to life than CS" option
  (or even if you didn't), you should be particularly careful to read over 
  the answer key and
  talk to me about anything that did not make sense.
* Please be careful about indentation and formatting - Your indentation
  and formatting can make stuff more readable, or it can make stuff
  less readable.
* No using 'define' in the middle of another 'define'.  (You now have
  'let' and 'let*', so it should not be necessary.)

Notes on Lab Writeup 4
* Nope

Notes on Homework 5
* image-show-variants (problem 1) should make one image per transformer.
* The repeat operation has the form
        (repeat TIMES PROCEDURE OPTIONAL-PARAMETERS)
  * The procedure needs to be a procedure (named with define, named with
    let, or anonymous)
  * The parameters are optional

Questions on the reading
* Goal: Operations that let you choose between actions
  (if test consequent alternative)
  (when test step step step step)
  (cond ...)