CSC207.01 2014S, Class 33: An Introduction to Linear Structures
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_Overview_

* Preliminaries.
    * Upcoming work.
    * Admin.
    * Questions on the exam.
* Today's concepts.
    * Linear structures.
    * Stacks.
    * An application of stacks: Matching parens.
* Lab.

Preliminaries
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### Upcoming work

* Today's writeup: Exercise 4.
* Reading for Tuesday: Queues.
* Exam 2 due Friday in class.

### Admin

* I am returning the makeups for exam 1.
    * 4 of you increased your grade
    * 8 of you had no change.  Many of your average functions still had
      bugs, many of your replacement functions were still O(n^2).
* Review session Tuesday night at 7 (we think)
* CS study break tonight (I think)
* Consider running for the SEPC
* Get ready to vote on T-Shirts (the Curried Lamb-Duh T-shirt is clearly
  the best)

### Extra Credit

* Convocation, Wednesday, noon: Elizabeth Colbert (the Sixth Extinction?)
* CS extras Thursday: ???
* CS table Friday: TBD
* Dance Troop performances in Chicago this weekend.
    * Double extra credit, because it involves figuring out where

### Questions on the Exam

_Will you write some unit tests for the filtered list `remove` method?_

> I'll try.

Linear structures
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New ADT: Linear Structure

* What is the big purpose/philosophy?
    * A very simple mutable collection
* What methods should it have?
    * Add something
    * Get something
* Use cases: What problems would it be useful for? 
    * Sam's office
    * To do list, job jar, ...

Interesting issue: We create different ADTs by specifying *policies* for the
get method.

* Random: Give me something unpredictable.
* LIFO: Give me the most recently added thing still in the stucture
* FIFO: Give me the least recently added thing still in the structure
* Priority: Give me the highest priority (e.g., smallest, largest) thing

Four policies -> Four new ADTs.

Stacks
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* What is the philosophy:
    * A simple linear structure with a LIFO policy
* Methods
    * put(T val)
    * T get() - get/remove most recently added value that still remains
* Use cases:
    * Matching.  When you see an opening value, push on the stack.  When you
      see a closing value, pop it off the stack.
    * Function calls in almost any modern language.
    * Model portions of a cafeteria

Lab
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