Re: [jbovlaste] berbere, berberi

On Sat, Jan 26, 2013 at 3:24 AM, Jorge Llambías <jjllambias@gmail.com> wrote:

On Fri, Jan 25, 2013 at 1:17 PM, John Cowan <cowan@mercury.ccil.org> wrote:
> Jorge Llambías scripsit:
>
>> Surely that can't have been the reason. How did you prove that
>> decompositions with CCVCy- rafsi were unambiguous, and why wouldn't
>> the same method of proof work for CCVVCy-? The proof seems just as easy.
>
> Our proof engine was Nora, who reduced the existing morphology to a
> set of cases. Looking at them, we were reasonably sure the CCVVCy
> set didn't break the proof, but Nora didn't have time to check it.
> Those cases weren't published anywhere I know of, and are either lost
> or buried in Bob's paper archive, which amounts to the same thing.
> If you want to produce and publish such a proof, I'm sure Lojbanists
> everywhere would be happy to have it.

It seems trivial:

If CCVVCy- is at the beginning of the string, no initial cmavo form
can drop as a cmavo, so there's no chance of tosmabru type issues.

There's also no chance of slinku'i type issues because CVVCy, VVCy,
VCy, Cy are not valid rafsi.

If it's not at the beginning of the string, no initial segment of
CCVVCy- could be part of another rafsi for the same reason that no
slinku'i is possible

That's the proof. What am I missing?

>> > Note that a PEG grammar, unlike a YACC grammar, does not prove this,
>> > because PEG grammars silently override ambiguities using the rule
>> > "first = best". That isn't good enough for Lojban morphology,
>> > so I consider the CLL proposal a dead letter.
>>
>> The YACC grammar doesn't handle morphology at all, so I fail to see
>> how this has anything to do with the issue.
>
> I was speaking generally. YACC grammars can provide a proof of
> unambiguity in certain circumstances. PEG grammars cannot: they are
> not in that business.

PEGs are unambiguous by construction, they don't need to be proved
unambiguous, since they can't fail to be unambiguous.

Whatever issues you may have with the PEG grammar for Lojban (and I
can think of some) they cannot be about potential ambiguities, it
can't have any.

>> If the PEG morphology isn't good enough for Lojban, then Lojban doesn't
>> have a formal morphology at all, because the PEG is the only one we
>> have so far.
>
> The fact that the morphology hasn't changed means that the old proof
> is still valid, even though we no longer have access to it. That's an
> unfortunate state of affairs, but it's where we are.

Not really. It's obvious to me that Lojban's morphology is
unambiguous, but that doesn't mean that any old (purported) proof of
its unambiguity is valid. I happily accept Nora's proof was probably
valid though. It's also equally obvious that CCVVCy- rafsi or the
extended 'y- rafsi don't cause ambiguity.

BTW, the PEG grammar doesn't single out CCVVCy- rafsi. It accepts all
final-vowel-dropping fu'ivla rafsi that don't cause ambiguities.
CCVVCy- is just one particular instance of those.

mu'o mi'e xorxes

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