Wrong backtracking algorithm

[62]

Hello! I'm find that expression like:

start = (term? term)? term
term = [0-9]

don't correct work with nested optional terminals. It cannot recognize two digit string (11). One and three digit is ok.

Analogous regular expression work fine:
([0-9]?[0-9])?[0-9]

I think you use "possessive quantifiers" backtracking algorithm for optimize performance, like:
([0-9]?+[0-9])?+[0-9]
but in common case it is not correct.

How can I switch to classic "greedy"?

Thank you very much for your work!

[otac0n]

This is not how PEG grammars work. PEG grammars are a short hand for recursive descent parsers, which do not backtrack in the same way that regular expressions do.

This is intentional.

[otac0n]

Also, see #105 and #57.

[62]

Sorry, name PEG misleading me (and switch BNF alternative "|" to PEG ordered choice "/") This is common for "parsing strings" grammars unlike BNF "constructing string" (context free).

[dmajda]

As explained above, this is not a bug. Closing.