private Object parseRecursive(StringTokenizer st) {
List<Object> currentSequence = new ArrayList<>();
Object lastParsed = null;
while (st.hasMoreElements()) {
String s = st.nextToken();
switch (s) {
case " ": // split on blanks
currentSequence.add(lastParsed);
break;
case "?":
lastParsed = grammar.zeroOrOne(lastParsed);
break;
case "*":
lastParsed = grammar.zeroOrMore(lastParsed);
break;
case "(":
lastParsed = parseRecursive(st);
break;
case ")": // current group finished
return finish(currentSequence, lastParsed);
case "'":
lastParsed = Token.getFromDescription(st.nextToken("'"));
st.nextToken("'?*() "); // '
break;
default:
lastParsed = s; // rule name
break;
}
}
return finish(currentSequence, lastParsed);
}
