Lojban In General

OK, I caved and implemented a subset of left recursion. It was
surprisingly easy. The PEG now checks to see if the first item in the
first sequence in the first option is a reference to itself. If so,
that production will try to match the other, non-recursing options
first, and if it finds a match, will try to match the first option
using the match from the other option as the value of the recursive
item. It repeats this until it can't eat any more text. The changes I
made to the grammar to use this feature follow. They're quite
regular--decrement the number in the first item, remove asterisk, and
add an option for the next production.

-statement-1 <- statement-2 (I-clause joik-jek statement-2?)*

+statement-1 <- statement-1 I-clause joik-jek statement-2? / statement-2

-bridi-tail-1 <- bridi-tail-2 (gihek !(stag? BO-clause) !(stag?
KE-clause) free* bridi-tail-2 tail-terms)*

+bridi-tail-1 <- bridi-tail-1 gihek !(stag? BO-clause) !(stag?

KE-clause) free* bridi-tail-2 tail-terms / bridi-tail-2

-terms-1 <- terms-2 (pehe-sa* PEhE-clause free* joik-jek terms-2)*

+terms-1 <- terms-1 pehe-sa* PEhE-clause free* joik-jek terms-2 / terms-2

-sumti-2 <- sumti-3 (joik-ek sumti-3)*

+sumti-2 <- sumti-2 joik-ek sumti-3 / sumti-3

-selbri-3 <- selbri-4+

+selbri-3 <- selbri-3 selbri-4 / selbri-4

-selbri-4 <- selbri-5 (joik-jek selbri-5 / joik stag? KE-clause free*
selbri-3 KEhE-clause? free*)*

+selbri-4 <- selbri-4 (joik-jek selbri-5 / joik stag? KE-clause free*

selbri-3 KEhE-clause? free*) / selbri-5

tanru-unit-2 <- blah blah blah blah ... /
- NU-clause NAI-clause? free* (joik-jek NU-clause NAI-clause? free*)*
subsentence KEI-clause? free*

+ nu-clauses subsentence KEI-clause? free* + +nu-clauses <- nu-clauses joik-jek nu-nai / nu-nai + +nu-nai <- NU-clause NAI-clause? free*

I'm planning on using this feature, xorxes. i mi ba nelci lo nu je ka
jo du'u palci pilno .ui

-tag <- tense-modal (joik-jek tense-modal)*

+tag <- tag joik-jek tense-modal / tense-modal

-stag <- simple-tense-modal ((jek / joik) simple-tense-modal)* /
tense-modal (joik-jek tense-modal)*

+stag <- stag (jek / joik) simple-tense-modal / simple-tense-modal / tag

Now these two I'm not entirely sure about. But I don't think it hurts
anything too much. On 'stag', besides the recursion I also changed the
last option to just be a reference to 'tag', since the sequences were
identical.

I made these changes several days ago and haven't seen any problems
yet, though that's not a sure indicator of anything. So I don't think
there are any gross errors in here.

Chris Capel
--
"What is it like to be a bat? What is it like to bat a bee? What is it
like to be a bee being batted? What is it like to be a batted bee?"
-- The Mind's I (Hofstadter, Dennet)

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On Sun, Jun 22, 2008 at 7:15 PM, Chris Capel <pdf23ds@gmail.com> wrote:

> +
> +nu-clauses <- nu-clauses joik-jek nu-nai / nu-nai
> +
> +nu-nai <- NU-clause NAI-clause? free*
>
> I'm planning on using this feature, xorxes. i mi ba nelci lo nu je ka
> jo du'u palci pilno .ui

If I understand correcty, that means you will like ice-cream, right?
Since nothing can be both an event and a property, I take it that
{lo nu je ka jo du'u ...} could be something that is neither an event
nor a property, and also not a du'u. Ice-cream, for instance.

mu'o mi'e xorxes

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On Sun, Jun 22, 2008 at 7:15 PM, Chris Capel <pdf23ds@gmail.com> wrote:

>
> -tag <- tense-modal (joik-jek tense-modal)*
> +tag <- tag joik-jek tense-modal / tense-modal
>
> -stag <- simple-tense-modal ((jek / joik) simple-tense-modal)* /
> tense-modal (joik-jek tense-modal)*
> +stag <- stag (jek / joik) simple-tense-modal / simple-tense-modal / tag
>
> Now these two I'm not entirely sure about. But I don't think it hurts
> anything too much. On 'stag', besides the recursion I also changed the
> last option to just be a reference to 'tag', since the sequences were
> identical.

In fact, you could just do:

stag <- tag

or just remove "stag" from the grammar and replace everywhere with "tag".
The PEG eliminated the distinction that existed between them, as it was
a consequence of the LALR(1) restriction.

mu'o mi'e xorxes

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On Sun, Jun 22, 2008 at 05:15:46PM -0500, Chris Capel wrote:
> OK, I caved and implemented a subset of left recursion. It was
> surprisingly easy. The PEG now checks to see if the first item in
> the first sequence in the first option is a reference to itself.
> If so, that production will try to match the other, non-recursing
> options first, and if it finds a match, will try to match the
> first option using the match from the other option as the value of
> the recursive item. It repeats this until it can't eat any more
> text. The changes I made to the grammar to use this feature
> follow. They're quite regular--decrement the number in the first
> item, remove asterisk, and add an option for the next production.

This would be your own PEG parser generator, then? Sorry, I haven't
been following the thread.

You might want to look at whatever the Rats! guy did; his stuff also
automatically deals with left-recursion, but I think maybe in a
slightly more structured fashion? He's pretty approachable, you
might want to ask him.

-Robin

--
Lojban Reason #17: http://en.wikipedia.org/wiki/Buffalo_buffalo
Proud Supporter of the Singularity Institute - http://singinst.org/
http://www.digitalkingdom.org/~rlpowell/ *** http://www.lojban.org/

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On Tue, Jun 24, 2008 at 5:21 PM, Robin Lee Powell
<rlpowell@digitalkingdom.org> wrote:
> You might want to look at whatever the Rats! guy did; his stuff also
> automatically deals with left-recursion, but I think maybe in a
> slightly more structured fashion? He's pretty approachable, you
> might want to ask him.

This is the paper I followed to implement direct and indirect left
recursion support in my own peg grammar implementation:

http://www.vpri.org/pdf/packrat_TR-2007-002.pdf

I think Rats uses a method of grammar transformation iirc and doesn't
deal with indirect left recursion. It's been a while since I used it
though, so that might have been dealt with.

Chris
--
http://www.bluishcoder.co.nz

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