help with pypeg2?
Neal Becker
ndbecker2 at gmail.com
Fri Feb 6 13:26:44 EST 2015
Ian Kelly wrote:
> On Fri, Feb 6, 2015 at 7:55 AM, Neal Becker <ndbecker2 at gmail.com> wrote:
>> Trying out pypeg2. The below grammar is recursive. A 'Gen' is an ident
>> followed by parenthesized args. args is a csl of alphanum or Gen.
>>
>> The tests 'p' and 'p2' are fine, but 'p3' fails
>> SyntaxError: expecting u')'
>>
>>
>> from __future__ import unicode_literals, print_function
>> from pypeg2 import *
>>
>> ident = re.compile (r'[a-z]+')
>> alphanum = re.compile (r'[a-z0-9]+')
>> num = re.compile (r'[0-9]+')
>>
>> class args (List):
>> grammar = maybe_some ( csl ([alphanum, Gen]))
>
> I'm not familiar with pypeg2, but should this use optional instead of
> maybe_some? The csl function already produces a list, so the result of
> maybe_some on that would be one or more consecutive lists.
>
> Also, it looks from the docs like it should just be "csi(alphanum,
> Gen)" (no list in the arguments).
It didn't work without [list..] (even trivial examples did not work without it).
I don't know if it's broken, I though csl (*args) should mean a comma-sep-list
of _any_ of the *args, but it doesn't work. [list] means alternatives, and does
seem to work (for simple examples).
--
-- Those who don't understand recursion are doomed to repeat it
More information about the Python-list
mailing list