CSC153 Class 44: More List ADT Design

Overview
* Comparing list design
* Deletion and iteration
* Implementing lists with arrays

Notes
* Are there any questions on the exam?
* Reminder: Fun movie on Monday
* Admittees visiting (lots and lots of them)

Why should these admittees come here?
* "Sam's great"
* Professors are fun and interesting and make sarcastic jokes
  and care  and bring their kids to class.
* Plans, an aspect of the cool Grinnell culture (and self
  governance)
* Relaxed intellectual atmosphere
* Lots of interesting traditions
  + National pipe cleaner day
  + Titular Head - Student film-making contest
  + Plans: Fun online interaction board
  + Self governance: Students determine rules of behavior
  + Grinnell Relays
  + Alice
* College vs. Graduate schools
  + No teaching by graduate students
  + Faculty who make teaching their primary responsibility
  + Opportunities to do research with faculty
* Careful language: "First year" vs. "freshman", "Second year"
  vs. "sophomore"
* Lots of chances to interact with students from multiple
  countries (and to go to multiple countries)
  + 10% of campus is non-American
  + 60% of students study abroad
* We teach Scheme in the first course.  Scheme is a really
  cool language at Grinnell.  Elsewhere it's evil.
* Grinnell students never form opinions about things (like
  Scheme) without encountering them first.

----------------------------------------

Lists
  Collections that you can step through
  Vs. Collections you may not step through
    Primary operation: Does this set contain this value
  Vs. Indexed Collections
    Accessing a specific element by number

----------------------------------------

Official sun.Java design decision:
  Iterators (Cursors) provide a next() procedure that
    simultaneously returns the next() objectr and advances
    the iterator.
vs. Official CSC153 design decision
  advance() advances without returning
  getValue() gets without advancing

How to print a list:

Java
  while (thingy.hasNext())
    out.println(thingy.next());

Ours

  while (!thingy.atEnd()) {
    out.println(thingy.getValue());
    thingy.advance();
  }

Whoops ... doesn't print the last element

  do {
    out.println(thingy.getValue());
    thingy.advance();
  } while (!thingy.atEnd());

Crash and burn for empty lists (bad).
Still doesn't print last element!

  while (!thingy.atEnd()) {
    out.println(thingy.getValue());
    thingy.advance();
  }
  out.println(thingy.getValue());

Prints the last element
Crashes and burns for empty list
  But we don't have cursors for empty lists.

----------------------------------------

What happens to a cursor if you delete an element from the
list?

Sam says: "All cursors are invalid."
Students say: "Blech".
Arjun investigated what Sun Java does.
  delete "might" throw a "ConcurrentModificationException"
  Sun says the same thing as Sam.