StackOverflowError in getAlphabet() on large grammars

[RodionovMaxim05]

When processing large grammars, getAlphabet() throws a StackOverflowError due to deep recursion. Even increasing the JVM stack size to 12 MB (-Xss12m) does not resolve the issue.

Steps to Reproduce

1. Download the attached files parenthesesList.txt and bracketsList.txt with symbol IDs.
2. Use the following grammar definition:

import java.io.File

fun dyckGrammar(
): Grammar {
	val parenthesesIds = File("parenthesesList.txt").readLines()
	val bracketsIds = File("bracketsList.txt").readLines()

	return object : Grammar() {
		val S by Nt().asStart()

		init {
			var alternatives: Regexp = Epsilon or (Term("normal") * S)

			for (id in parenthesesIds) {
				val open = "op--$id"
				val close = "cp--$id"
				alternatives = alternatives or ((Term(open) * S * Term(close)) * S)
			}

			for (id in bracketsIds) {
				val open = "ob--$id"
				val close = "cb--$id"
				alternatives = alternatives or ((Term(open) * S * Term(close)) * S)
			}

			S /= alternatives
		}
	}
}

3. Call the grammar and trigger the error:

val grammar = dyckGrammar()
grammar.rsm

Exception:

Exception in thread "main" java.lang.StackOverflowError
  at org.ucfs.grammar.combinator.regexp.Regexp$DefaultImpls.getAlphabet(Regexp.kt:30)
  at org.ucfs.grammar.combinator.regexp.Alternative.getAlphabet(Alternative.kt:6)
  ...

Attached Files

parenthesesList.txt
bracketsList.txt