Lab #7: Trees and More

Part I: Fun with the Java Library.

1. The file 

	~cs61b/hw/lab7/ListHacker.java 
   
   has some skeleton methods for you to fill in and a dummy main program. 
   Fill in the methods.  The idea is to peruse the List class in 
   the Java library, as well as the Collections class and the Arrays class,
   looking for methods that do the work for you without your having to write
   any loops, recursive calls, etc.

2. Test your methods with the debugger.  First, try stopping the 
   program by hand at the "stop here" point in the main program and then
   using the debugger to build lists and call your functions.  The
   local variables in main are a handy place to put them.  How can 
   you print the lists your functions produce?  

3. Part 2 rapidly gets tedious.  GJDB has a 'source' feature that will
   read debugging commands from a file.  Try building such a file 
   with tests of some of your list functions.  Then stop in the main 
   program and use the 'source' command in the debugger to run your
   tests.

Part II: Trees 

On page 94 of the Data Structures Into Java reader, there is 
a definition of eval on an expression tree.  You will find a 
modified version in 

   ~cs61b/hw/lab7/Expr0.java

along with some supporting code. 

1. There is no Makefile supplied.  Provide one.

2. The definitions of toString and read are incomplete, AND THERE ARE 
   OTHER BUGS.  Fill in the missing code and fix the bugs (see the 
   comment on the main program).

Now we'll create a re-implementation of Expr0 called Expr, but this we'll 
do it "the object-oriented way".

3. Copy over the template 
   
 	~cs61b/hw/lab7/Expr.java

   Modify it to do the same thing as Expr0.  You will have to add
   new classes (either in Expr.java or in separate files).
 
   HOWEVER, do NOT add any more 'if', 'while', 'for', or 'switch'
   statements or any more ?: operators; just use object-oriented
   stuff.