Overview

• Admin.
• Design of ADTs: Minimalist vs. Maximalist
• Arrays, Continued.
• Modeling Strings.
• And Numbers.

Admin

• Warning! Friday the 13th falls on a Friday this month.
• Reminder: Mentor session TONIGHT at 8:30 pm
• Although there are links (broken?) to labs for yesterday and today, we won't be holding those labs. (Parts of the labs are in the homework assignment.) I do hope to hold lab on Friday.
• Nationwide will be on campus next Tuesday to talk about (and recruit for) jobs and internships. There's a 4:15 talk, but there's also a noon lunch for Math/Stats and CS majors. Signs should be around.
• Reading for Friday (expect it Thursday; I'll send email)
  • Input and Output
• It's been noted that the kinds of questions I'm asking on your homework assignment are a lot like coding questions that get asked in interviews. The overlap is not intentional. (I don't object to it, but I just choose questions that I think will challenge you appropriately.)
• If you are not on the CS mailing list and want to be on it, let me know and I'll get you added.
• I see only one (worried) prologue for HW3.
  
  • Here's a hint on the last problem: Recursion is likely to be your friend, at least at first.
  • Experiments should suffice FOR THIS PROBLEM ONLY.
• EC opportunities:
  • Humanities Center Speaker Sarah Hendron, TONIGHT, 7:30 p.m., JRC101 Waking the Machines: Art, Design, and Adaptive Technology
  • Learning from Alumni 2:15-4:05 Thursday: Ian Lunderskov '08
  • We think the Matt Atherton Thursday extra is NOT happening. Sorry.
  • CS Table, Friday: Trusting Trust.
  • More?
• No EC, but a chance to talk about Feminist Action Coalition at 8pm tonight in Younker

Minimalist vs. Maximalist ADT Design

Why Minimalist?

• Laziness.
• Less for your audience to read.
• All your clients should need are the building blocks; you can't predict every possibility, so why try?
  • And your clients will benefit from having to implement them, particularly if they are novices
  • Helps the client learning curve
• Anti-max: The more you have to implement, the more restricted the implementation
  • And you'll make tradeoffs
  • Example: Java has an ArrayList type: It's indexed like arrays, but it allows you to insert in the middle, like lists
• Anti-max: The more you have to implement, the less likely you are to try something new

Why Maximalist?

• Experienced programmers will make fun of you if you don't include
  the procedures they expect
• As a client programmer, you can know that you will have most, if not all of the utility procedures you will need.
  • Client programmers are more efficient
• Saves total programmer time

Sam likes minimalist approaches, at least for novice implementers

Arrays, Continued

• Start with a few basic procedures:
  • Create/initialize/declare
  • Get ith element
  • Set ith element
  • Get length/size
• Maximalists might add
  • um - fill the array with u's and m's
  • convert to and from lists
  • copy values from an array to another array (yeah, a for loop would do the job, but ...)
    • A clever implementation might do this as a bit copy or in parallel
  • apply proc to each element, mutating each element
    • Or returning a new array
  • shuffle - rearrange randomly
  • member; indexOf
  • sort
  • print
  • Grab a subsection of an array
• A hidden issue
  • collections of values
  • homogeneous (simple; necessary for the "jump to start + width*index)
  • indexed by integers (typically, starting with 0)
  • We've implicitly added "Fixed size"

Vectors

Java provides Vectors, which are dynamic arrays.

Declare

   Vector<TYPE> name;

Initialize

    new Vector<TYPE>(SIZE)

Set

    name.set(*index*, *val*)

Get

Length? (# elements vs capacity)

• Read the documentation for more information.

Strings

What are strings? (Purpose/Philosophy)

• Human-readable ordered collections of characters (maybe ASCII, maybe EBCDIC, maybe Unicode)
• Practica: Interact with human beings

• Procedures (minimalist)

  • read them (input)
  • print them (output)
  • create new ones (with input of ...?)
  • compare alphabtically (given your local version of alphabetical)
  • length
  • check if empty (or does length == 0 suffice?)
  • concatenate
  • get individual elements
  • substring
  • mutate a letter

• In Java, strings are IMMUTABLE. (So they can share memory.)

  eyes.println("Hi, " + studentOne);
  eyes.println("Hi, " + studentTwo);
  

• When you want string-like things that are mutable, use StringBuffers

  String val = "Hello";
  String newval = val + val;
  eyes.println(val.charAt(i));
  eyes.println("There are " + val.length() + " characters in val");
  if (val.compareTo(other) < 0) {
    eyes.println (val + " comes before " + other);
  }
  

Numbers

Not covered