CSE 509  --  HW #2
==================

Date Due:  Monday, 21 January 2002

Goals:

- Write and debug some Smalltalk code.
- Gain familiarity with the Browser, Debugger and Inspector.
- Gain familiarity with the actual Smalltalk class hierarchy.


Note:  

It is okay to work together in playing with the user interface, but do not
work together on writing the methods or on the class hierarchy in Part 2.
The code you supply must be written by you alone.


Part 1  -  Smalltalk Programming:

(1) Use the browser to type in the class Tree.  Create a new class category,
Tree-Application, and put the class there.  The code for class Tree is in the
class lecture notes.

(2) In a workspace, practice evaluating some expressions.  Build some trees
and exercise all of the Tree methods.

(3) Try "inspect"ing some Tree objects.  Create a Tree with several sub-nodes
and use the "inspect" menu command to bring up an "inspector."  Walk through
the tree nodes and figure out how the inspector works.

(4) Artificially introduce bugs in Tree and play with the "debugger."  (Try
including the statement "self debug" within some method.  Then, invoke the
method.)

(5) Write a method, called height, that returns the height of the receiver
(an instance of Tree).  (The height of a tree with no sub-trees is 1.)  Test
your method.

(6) Write the remove: aString method and test it.  There are some special
cases that can occur when attempting to remove nodes from the Tree.  Be sure
your method comment tells how your method deals with these cases.

(7) In an "ordered tree," all nodes are ordered by their labels.  In such a
tree, an in-order traversal should visit the nodes in alphabetical order.

- Create a subclass of Tree called "OrderedTree."
- Write an addInOrder: aString method.
- Re-implement methods as necessary to make use of the fact that the tree is
  ordered.
- In the class comment of OrderedTree, document a consistent interface such
  that, if a user of OrderedTree followed the prescribed protocol and only sent
  the messages listed in the comment, the order of the tree would never be
  violated.



Part 2  -  Smalltalk Class Hierarchy:

In order to become a proficient Smalltalk programmer, you must become familiar
with the existing classes and methods.  Below is a list of what I feel are the
most important classes and methods in the Smalltalk class hierarchy.
Obviously, this is a subjective list.  The goal of this exercise is to focus
your attention on the most important methods and to encourage you to learn a
useful subset of the class hierarchy.

For each class in the list, indicate what its superclasses are.  For each
method, provide a short (one sentence) description of its function.  If the
method takes an argument, describe it.  For example:
  Dictionary -- superclasses: Set, Collection, Object
    associationsDo: -- Evaluate the argument once for each key-value pair.
                       The argument should be a block taking a single argument,
                       which will be an Association.

You may get the answers from either external documentation or by browsing
Smalltalk itself.  

Note: some methods may be defined in a superclass of the class I listed them
in.  I listed the methods where they are frequently used.  For example, the
binary operator "," is defined in SequenceableCollection, but I rarely use it
for anything other than concatenating Strings.  Thus, it is included after
String.


Object
  isNil
  notNil
  =
  ~=
  ==
  ~~
  class
  isKindOf:
  error:
  shallowCopy
  deepCopy
  printOn:
  printString
  new (class method)

Boolean
  not
  and:
  &
  or:
  |

Collection
  add:
  addAll:
  do:
  size
  isEmpty
  with:with:with: (class method)

OrderedCollection
  at:
  first
  last
  addFirst:
  addLast:
  removeFirst
  removeLast

Set
  add:
  remove:

Dictionary
  at:
  at:ifAbsent:
  at:put:
  includesKey:
  do:
  associationsDo:

Association
  value
  key

Array
  at:
  at:put:
  new: (class method)

String
  ,
  printOn:

Character
  cr (class method)
  tab (class method)

WriteStream
  nextPut:
  nextPutAll:

Random
  Next

BlockContext (Every "block" is an instance of this class.)
  value:value:value:
  whileTrue:


Number
  <
  <=
  >
  >=
  =
  +
  -
  *
  /
  //
  \\
  quo:
  rem:
  truncated
  rounded
  printString

Integer
  to:do:


What to hand in:

Part 1: File out the entire category Tree-Application, including both Tree and
OrderedTree classes.  Then e-mail that file to harry@cs.pdx.edu with subject
"OOP HW #2".  Please don't submit multiple copies.

Part 2: Hand-in a document.  Machine formatted output is preferrable to
hand-written output!  Please staple everything together in the upper-left
corner.  Be sure your full name is on the very top page.




Grading Criteria:

Part 1: How "pretty" is your code?  Is it well documented in complete English
            sentences?  Is it indented logically and neatly?
        How clear and logical is your code?  Or, does it contain unnecessary
            tests, unexecuted branches, etc?
        Is your code correct?
Part 2: How understandable are your specifications?  Are they short and sweet
            or are they imprecise, redundant, overly wordy, or just plain wrong?
        How much of the assignment did you complete?