[lojban] left recursion changes

["Chris Capel" <pdf23ds@gmail.com>]

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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