CSC297.Java 2003F, Class 9: Arrays

Admin:
* I was thinking of diverging from Mr. Bishop's syllabus, but decided not to (yet).
* I'd be interested in seeing your Rational classes.
* Let's look at Mr. Bishop's assignment and decide what we need to add to ours.

Overview:
* What is an array?  (What is a vector in Scheme?)
* Scheme vectors vs. Java one-dimensional arrays
* Java arrays vs. Java vectors

Some notes on Rational numbers

A nice way to create a "whole rational number"
	public Rational(long num) {
	  this.numerator = num;
	  this.denominator = 1;
	} // Rational(long)

A more interesting problem: Convert a real to a rational.
* Template
	public Rational(float num) {
	} // Rational(float)
* Strategy one: Use simplify.  Won't work.
* Strategy two: Repeatedly multiply by 2 until no fractional part.
	double n = num;
	long d = 1;
	// As long as there is a fractional part
	while (n - Math.floor(n) > 0) {
	  // Increment both n and d by the same factor
	  n = n * 2;
	  d = d * 2;
	}
	this.numerator = (long) n;
	this.denominator = d;
	this.simplify();

* Some morals:
  * For lots of similar tests, write a helper function
  * Think about a variety of cases
  * Since computers think in base two, your algorithms should, too

/On to Bishop's stuff/

* Zero-parameter constructor.  Easy.
* String-based constructor.
  * Look at the String class.  Helpful methods?
    * indexOf(ch) finds the position of the /
    * substring(int beginIndex, int endIndex) extracts numbers
    * substring(int beginIndex) also helps

	public Rational(String str) {
	  int pos = str.indexOf('/');
          this.numerator = str.substring(0, pos-1);
	  this.denominator = str.substring(pos+1);
	  this.simplify();
	} // Rational(String)