Hi Kaspar,
Thanks for the quick response, splitting up expr into a rule to break the
recursion solves it. All clear now.
Vieni per caso dalla Svizzera? (Sorry if not, I just guessed Florian knows you
from Switzerland because of the name… I'm in Melbourne too).
Cheers,
Chris
On 04/11/2011, at 9:11 PM, Kaspar Schiess wrote:
> Hei Chris,
>
> You have to think about what moves the parse forward, just as if you were
> coding it by hand. The two relevant functions would look something like this
> (in your grammar):
>
> def parse_sum
> parse_expr or return false
> parse_wsp
> parse('+') or return false
> parse_wsp
> parse_expr
> end
>
> def parse_expr
> return true if parse_sum
> return true if parse_add_call
> parse_t_int
> end
>
> (Assuming that parse functions return a boolean indicating their success.) So
> what you have there is direct mutual recursion between expr and sum. And put
> like this (in code), it is easy to see, isn't it?
>
> I guess your sum doesn't really allow any kind of expression in front, but
> rather something that can be an element of a sum, like integers or function
> calls. That avoids the recursion.
>
> Here's something that works, maybe that helps you along as well:
> https://gist.github.com/1339032
>
> regards,
> kaspar
>
