private int lexInt() {
		boolean notDone = true;
		String s = "";
		while (notDone) {
			if (currentLine.length() > 0) {
				char c = currentLine.charAt(0);
				if ((c >= '0') && (c <= '9')) {
					s += c;
					currentLine = currentLine.substring(1);
				} else {
					notDone = false;
				}
			} else {
				notDone = false;
			}
		}
		if (s.length() == 0) {
		    throw new RuntimeException("Trying to find interger when none is present.");
		}
		return Integer.parseInt(s);
	}