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I've isolated a 3-rule pattern, where I'd expect the parser to succeed for a given input, but it fails instead. The sample grammar:
RuleA ::= RuleB.RuleB ::= IDENTIFIER | RuleC '.' IDENTIFIER .RuleC ::= RuleB | RuleA .The implementation:
importscala.util.parsing.combinator._importscala.util.parsing.combinator.syntactical.StandardTokenParsersobjectSimpleParserextendsStandardTokenParserswithPackratParsers { lexical.delimiters++=List(".","$")lazyvalruleA:PackratParser[String]= ruleB<~"$"lazyvalruleB:PackratParser[String]= (ident||| ruleC~>"."~> ident)lazyvalruleC:PackratParser[String]= (ruleB||| ruleA)defmain(args:Array[String])= { println(ruleA(newPackratReader(new lexical.Scanner("x.x$")))) }}
It fails for inputx.x$, telling me that it expects a$ instead of the..
For me, this seems to be a problem with how indirect left-recursion is handled. I'm not sure if theoriginal algorithm is incapable of handling this pattern, or this is an implementation bug.
Edit:
I've accidentally used| (first matching alt.) instead of||| (longest matching alt.), I've fixed that in the code, but doesn't change the outcome.
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