CSC151 2007S, Class 40: Pairs and Pair Structures

* I will continue to reserve time at the start of class for discussion of campus issues.

Admin:
* If Patch really loved us, he'd stick to a timetable
* Thoughts about the second half of Quiz 8?
* Are there questions on Assignment 9?
* The intended lesson for Assignment 9 gets lost in the cost of file I/O.
* We will have visitors in this class on Tuesday and Wednesday (at least) 
  as part of my triennial review.
* Reading for tomorrow: Deep Recursion.

Overview:
* Memory and naming.
* Pairs and cons cells.
* Why care?
* Lab!

==Review: Vectors==

* A mutable collection (mutable = you can change things)
* Of fixed size: Once you've set a length, you're stuck with it
* Indexed: Fast access for retrieving and setting values

* Implementation: A chunk of memory divided into fixed-size pieces,
  each piece references a Scheme value

==Today: Representing Lists==