CSC151, Class 54: Objects Lab

Overview:
* Lab
* Reflection

Notes:
* I imagine many of you are having a hard time right now,
  whether or not you knew Mr. Stefanov.  I know I am.
  Is there anything I can do to help?
* One thing (announcement was planned for tomorrow after evals): 
  I am not giving you a final.  I will drop your lowest exam grade.  
  That exam can be number 3.
  + If you want to wait until Friday to turn in exam 3, 
    that's fine.
  + Sorry for enabling procrastination.
* I still need extra credit summaries from many of you.
* Tomorrow: Evaluate the class.
* Friday: Meet at Dari Barn.
* Tonight at 6:30 p.m in Steiner 306: Pizza and Persians

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Reflection:

* Thanks for working hard on lab even though you know you're
  not being tested on this stuff.
* What is an object?
  A function with "state"
* What is state?
  Values that you may change.
* How do you give functions state?
(let ((private-state ...))
  (lambda () ...))
* This state is necessarily private.  No one else can access it.
* How do you return an object?
(lambda ()
  (let ((private-state ...))
    (lambda() ...)))