[antlr-interest] Double Left Recursion Update: Test case with working "double left recursion"

[Jan Finis]

Hi again,

as I mentioned in my last mail, I think that the problem with rules of 
the form

expr : expr expr;

is solvable because old Honey Badger was able to match them. I tried 
again and could confirm this. This grammar:


result : expr { System.out.println($expr.s); } EOF;

expr returns [String s]
	: 'x' { $s = "x"; }
	| e1=expr '?' { $s = $e1.s + "?"; }
	| e1=expr e2=expr { $s = "(" + $e1.s + " " + $e2.s + ")"; }
	;


parses correctly with an older 4.0ea version. I have uploaded this 
version here:
http://www-db.in.tum.de/~finis/antlr-4.0ea-complete-old.jar/

It does not only parse correctly, even the resulting parser is really 
able to match input without descending into a looping recursion.

I tested the resulting parser on the following input:

xxxxx?xx?xx


and the result was:

(x (x (x (x (x? (x (x? (x x))))))))

so the concatenation operation seems to be right associative, but it 
works perfectly fine :).

Best regards,
Jan