CSC151 2009F, Class 36: Vectors

Admin:
* Exam 2 due!
  * Don't forget to send the electronic copy
* Fun event Saturday a.m.: Grinnell Destination ImagiNation Fun Run/Walk.  
  More info outside my office or at the back of the room.
* Reading for Friday: Pairs and Pair Structures.
* CS Extra Thursday (4:30 p.m. 3821)
  Jun Ni, Ph.D., Associate Professor 
  Director, Center of Medical Imaging Informatics Department of Radiology, 
    Carver College of Medicine
  The University of Iowa
  A talk on the semantic framework for the description and classification 
    of data derived from health records and medical imaging.
* Sample solution for Quiz 8 returned.
* Assignment 7 is now ready.

Overview:
* Problems with lists.
* A solution: Vectors.
* Important vector procedures.

Quick summary of reading
* Common problem: Gather a group of information together
  * Dissimilar information to build a coherent whole: drawings
  * Lots and lots of similar values: colors, drawings, etc.
* Programming languages provide mechanisms for gathering information
  * Lists

TWO BIG PROBLEMS WITH LISTS
* Some common operations are SLOW
  * (list-ref lst 200)
* Some common operations are SLOW and HARD
  * "Change element #200 element of this list of colors to RGB-RED

The solution: Design another way to organize data!
* Vector (called an "array" in most languages)
* A way to group data
* Gives quick access to *any* element in the collection (by index)
* Mutableq
* You lose the ability to change the size of a vector.