zhaih commented on code in PR #12462:
URL: https://github.com/apache/lucene/pull/12462#discussion_r1286391478
##########
lucene/core/src/java/org/apache/lucene/util/automaton/RegExp.java:
##########
@@ -1067,22 +1071,44 @@ private boolean check(int flag) {
}
final RegExp parseUnionExp() throws IllegalArgumentException {
- RegExp e = parseInterExp();
- if (match('|')) e = makeUnion(flags, e, parseUnionExp());
- return e;
+ return iterativeParseExp(this::parseInterExp, () -> match('|'),
RegExp::makeUnion);
}
final RegExp parseInterExp() throws IllegalArgumentException {
- RegExp e = parseConcatExp();
- if (check(INTERSECTION) && match('&')) e = makeIntersection(flags, e,
parseInterExp());
- return e;
+ return iterativeParseExp(
+ this::parseConcatExp, () -> check(INTERSECTION) && match('&'),
RegExp::makeIntersection);
}
final RegExp parseConcatExp() throws IllegalArgumentException {
- RegExp e = parseRepeatExp();
- if (more() && !peek(")|") && (!check(INTERSECTION) || !peek("&")))
- e = makeConcatenation(flags, e, parseConcatExp());
- return e;
+ return iterativeParseExp(
+ this::parseRepeatExp,
+ () -> (more() && !peek(")|") && (!check(INTERSECTION) || !peek("&"))),
+ RegExp::makeConcatenation);
+ }
+
+ /**
+ * Custom Functional Interface for a Supplying methods with signature of
RegExp(int int1, RegExp
+ * exp1, RegExp exp2)
+ */
+ @FunctionalInterface
+ private interface MakeRegexGroup {
+ RegExp get(int int1, RegExp exp1, RegExp exp2);
+ }
+
+ final RegExp iterativeParseExp(
+ Supplier<RegExp> gather, BooleanSupplier stop, MakeRegexGroup reduce)
+ throws IllegalArgumentException {
+ Deque<RegExp> regExpStack = new ArrayDeque<>();
Review Comment:
Why we need stack/deque even?
If we need to further reduce call stack, then I think we need a **stack that
is shared across function calls** and some more rewrite.
But here I don't think we need stack and do any FIFO operations? Should be
just:
1. parse all the sub component
2. reduce them
So why not:
```
RegExp res = null;
do {
RegExp e = gather.get();
if (res == null) {
res = e;
} else {
res = reduce.get(flags, res, e);
}
while (stop.getAsBoolean());
```
I think this may alter the result a bit by changing it from `a | (b | (c |
d))` to `((a | b) | c) | d`, but for `union` `intersect` and `concat` the
affiliation shouldn't affect the correctness?
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