This is a response to Justin Chases's e-mail on the OMeta mailing list ("indirect left recursion woes"). The complete message is below:

	How can you author a grammar that can parse these:

	y()[0]
	y[0]()
	y[0][1]()[2]

	Without indirect left recursion?

	Callable = ??
	Index = Callable "[" "0".."9"+ "]",
	Invoke = Callable "(" ")",
	Reference = "a".."z"

	-- 
	Justin Chase 
	http://www.justnbusiness.com

How about this?

ometa P <: Parser {
  indexOrInvocation = indexOrInvocation:a "[" index:i "]" -> ["index", a, i]
                    | indexOrInvocation:f "(" ")"         -> ["call", f]
                    | reference,
  index             = "0" | "1" | "2" | "3" | "4"
                    | "5" | "6" | "7" | "8" | "9",
  reference         = "x" | "y" | "z"
}

And here's how you would parse your examples:

P.matchAll("y()[0]",       "indexOrInvocation")
P.matchAll("y[0]()",       "indexOrInvocation")
P.matchAll("y[0][1]()[2]", "indexOrInvocation")

Cheers,
Alex