[Python-Dev] Python 3.0 grammar ambiguous?

[Fabio Zadrozny]

>> I was wondering how does Python
>> disambiguate that... anyone has any pointers on it?
>
> That is easy to answer:
>
> py> parser.expr("f(*x)").totuple()
> (258, (326, (303, (304, (305, (306, (307, (309, (310, (311, (312, (313,
> (314, (315, (316, (317, (1, 'f')), (321, (7, '('), (329, (16, '*'),
> (303, (304, (305, (306, (307, (309, (310, (311, (312, (313, (314, (315,
> (316, (317, (1, 'x')))))))))))))))), (8, ')')))))))))))))))), (4, ''),
> (0, ''))
> py> symbol.arglist
> 329
>
> So much for the "how", I don't know why it makes this choice; notice
> that this is the better choice, though:
>
> py> f((*x))
>  File "<stdin>", line 1
> SyntaxError: can use starred expression only as assignment target


Yeap, very strange that it works... I can't get it to work in JavaCC.

I'm considering setting arglist as
((argument() [','])+  ['**' test])
| '**' test

Because it is able to handle the constructs removing the ambiguity,
and make things right semantically later on, but I don't like the idea
of being so different from the official grammar (although I'm running
out of choices).

Thanks,

Fabio