CSC151.01 2006S, Class 29: Vectors

Admin:
* Due: Project 1 Writeup.
* No homework during break.  
  No reading for Monday.  
  No coding for Tuesday.  
  Nothing.
  But you may get a survey when you return
* The things they didn't tell me: The original designers of the labs
  didn't expect most students to get all the way through, or even
  most of the way through
* Be careful: Friday the 13th falls on a Friday.

Overview:
* Problems with lists.
* A solution: Vectors.
* Lab.

Issue: We need to group data
Solution: Lists
* Easy to extend with cons
* Easy to take apart with car and cdr
* Lots of procedures
  Basic: cons, car, cdr, null, null?
  Advanced: reverse, list-ref, member, append
  Our own: member? , tally, ...
* Problem with lists
  * The cost of accessing an element depends on the position in the list
  * Without care, might write inefficient code

Solution to problems with lists: Vectors
* An indexed collection of values
  * Main operation: vector-ref
  * A lot like list-ref, but always "one step"
* Problem: Fixed size - Hard to "make larger"
* Other benefit: Mutable
  (vector-set! vec pos newval)