CSC151.02 2003F, Class 46: Insertion Sort

Admin
* Read "Merge Sort" for Monday.
* Finish the "guess a number" game before Wednesday at 5pm.
* The picture was me.
* Yesterday's class.
  * Visual
  * First-hand view
  * No computers
  * Exercise

Overview:
* Review of yesterday's class.
* Q and A.
* Lab
* Reflections

What did we learn yesterday?
* Lots of kinds of sorting
  * Quicksort: Split into small and big stuff, sort each half, join together
  * Merge sort: Split in half, sort each half, merge together using a more complex process
  * Insertion sort (in reading): Repeatedly insert things into the "correct" place in a sorted list.
  * Selection sort: Repeatedly select the smallest remaining element
* Why to sort
  * Support searching
  * Support characterizing the top 10% or something similar
  * Nothing better to do
* Relative efficiency and approximate formulae
* Relearned the term "transitive"
* Six P's of sorting
  * Parameters:
    * lst, a list
    * may-precede?, a binary comparator
  * Produces:
    * sorted, a list
  * Preconditions:
    * The comparison operation must be applicable to any two things in the list
    * may-precede? must be transitive
  * Postconditions:
    * The result list is a permutation of the original list (or "nothing has been added, nothing has been deleted, it's all just rearranged")
    * sorted is in order, each element is no bigger than the next element, in Scheme (may-precede? (list-ref lst i) (list-ref lst (+ i 1))) for all reasonable i.

What did you learn from the reading?  Or what questions do you have?
* What does revappend do?

Do the lab!