Lab #9: 

Part I: Project Progress

1. Generate Project 2 test sets (.in and .data) that test the step
   command.

2. Decide on the classes and fields you'll need to implement our QuadTrees.
   Document them and how they'll work in INTERNALS.  Implement the 
   constructor for QuadTree, and the add method.  

3. Document in INTERNALS how you intend to deal with the following
   problems:
	1. You must be able to perform setPosition on the Particles in
	   your QuadTree, and still have the neighborhood method of
	   QuadTree work correctly.

	2. You must be able to do (1) while iterating over the members
	   of the Set returned by contents() or neighborhood(). 

Part II: Sorting

1. The test-filter for Project 2 "canonicalizes" the output from the 
   within command, so that you can compare your output with some
   set of "official" output even if your program chooses a different
   order for that output.  Given output from within, such as

	(10,32) (10,29)
	(2,56) (01,54)
	(35,42) (36,41)
	(0,21) (1,20)

   (we'll stick to ints here) it sorts the two points on each line and
   then sorts the lines, using as its ordering for points the
   definition "p1 < p2 iff p1.x() < p2.x() or p1.x() == p2.x() and
   p1.y() < p2.y()", and using as its ordering for lines (pairs of
   points), "p1 p1' is less than p2 p2' if p1<p2 or p1=p2 and p1' <
   p2'" (two points are considered equal here if their x and y
   coordinates are equal).  Thus, the lines above become

	(0,21) (1,20)
	(1,54) (2,56)
	(10,29) (10,32)
	(35,42) (36,41)

   Fill in the skeleton canonical.java to read and sort a bunch of lines 
   like the above.  Use methods from the Java library (esp., see Collections,
   Arrays, and Comparator in java.util).  

2. Prepare test cases for your canonicalizer, and arrange that gmake check
   performs them.

3. Be prepared to explain to your TA anything in canonical.java, even the
   stuff we wrote.