cs230 Lecture Notes

Hi all.  These are my ex post facto notes for the last couple
of lectures.  I didn't write them ahead of time because I
wanted us to discuss the material in real time.

Here are some of the topics we have covered:

1) slurpy implementation

2) Alan Turing

3) data structures for the Markov algorithm

4) the space-time continuuuuuum

5) interning Strings

   Here is the code for interning Strings:

    public String internWord (String word) {
	String canon = (String) intern.get (word);
	if (canon == null) {
	    intern.put (word, word);
	    return word;
	}
	return canon;
    }

intern is an instance variable (a Hashtable) that was initialized
in the constructor.

Also, here is some code for generating random words from a
Hashtable (this is way more complicated than we would like):

    public String randomWord (Hashtable suffixes) {
	int count = totalSuffixes (suffixes);
	int x = randInt (0, count-1);
	Enumeration keys = suffixes.keys ();
	int total = 0;
	while (keys.hasMoreElements ()) {
	    Object key = keys.nextElement ();
            Integer value = (Integer) suffixes.get (key);
	    total += value.intValue ();
	    if (total > x) return (String) key;
	}
	// we should never get here
	return null;
    }

    public int totalSuffixes (Hashtable suffixes) {
	int total = 0;
	Enumeration keys = suffixes.keys ();
	while (keys.hasMoreElements ()) {
	    Object key = keys.nextElement ();
            Integer value = (Integer) suffixes.get (key);
	    total += value.intValue ();
	}
	return total;
    }

    // randInt: returns a random number between low and high,
    // including both endpoints
    public static int randInt (int low, int high) {
        while (true) {
            int x = (int)(Math.random() * (high-low+1) + low);
            if (x >= low && x <= high) return x;
        } 
    }


One other thing we talked about is the possibility of having
a "kill list" -- words that appear in the file but that we
should not include in the generated text.  I created a Hashtable
to contain all the bad words:

    public void makeKillTable () {
	kill = new Hashtable ();
	String[] badWords = {"verbatim", ".", ",", "x", "y", "i++", ".eps",
	                     "itemize"};

	for (int i=0; i< badWords.length; i++) {
	    kill.put (badWords[i], "k");
	}
    }