CSC151 2007S, Class 47: Insertion Sort

Admin:
* I will do my best to respect those of you who are silent today.
* Distributed: Exam 3 (due next Friday).
* EC for Saturday's Pride week march.
* EC for War Requiem concert, 7:30 Sat. Darby 
* Reading for Monday: Merge Sort (may be edited).
* The "overview" for today doesn't quite match because we did different
  things on Wednesday than I had planned.
* I'm not particularly pleased with the recent drop-off in attendance.
* NO QUIZ!

Overview:
* Some preparatory reflection on the reading.
* Lab.

== REFLECTION ==

What is the key idea in insertion sort?

* Want to sort something
* Do so by shuffling things around
* How do we shuffle?
  * One strategy: Shift neighboring things that are out of order
* Repeatedly insert values into
  * A list (if we're sorting lists)
  * The correct place in a vector (if we're sorting vectors)

How does insertion sort differ in lists and vectors?

* Lists: Build a new list and insert from left
* Vectors: Rearrange, insert from right

Why do we provide you with three different kinds of list-based insertion 
sort?

(define numbers-insertion-sort
  (lambda (numbers)

Only works with lists of numbers

(define list-insertion-sort
  (lambda (lst may-precede?)

Works with any kind of list
Generalizes numbers-insertion-sort

(define list-keyed-insertion-sort
  (lambda (lst get-key may-precede?)

Works with any kind of list