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Subject: [lojban] Re: Where is the latest/official PEG grammar?
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Date: Mon, 13 Apr 2020 15:43:22 +0000
In-Reply-To: <33fb11ad-6aa7-47be-adc5-049d9f6670a9@googlegroups.com> (Gleki
	Arxokuna's message of "Sat, 11 Apr 2020 07:35:55 -0700 (PDT)")
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Gleki Arxokuna <gleki.is.my.name@gmail.com> writes:

> PEG has its own deficiencies.

What deficiencies?

> True. PEG won't put us forward significantly.

Why wouldn't it?  Having a complete specification of the language seems
like it would be a HUGE step forward, to me.  From PEG, it would be but
a short distance to having a working, fully-correct parser.

>> Maybe that's what we're waiting for?  A proof that the PEG grammar is 
>> backward-compatible with the YACC?  
>
>
> Its not backward compatible by definition.

It would have to be.  Otherwise, currently (and historically)
grammatical Lojban wouldn't be grammatical under the new (PEG
specification of the) grammar.  Am I wrong?

>> IfIf so, the second half of Bryan 
>> Ford's thesis paper on PEGs describes how to transform parsing 
>> expressions into other forms which could be compared with the YACC.
>
>
> Transformation doesn't necessarily imply equivalence.

No, but it would render the PEG in a form which could be *compared* to
the YACC.  If you cut-out the morphology rules, and allow for changes
for handling elidable terminators and metalinguistic erasers, the
remainder (the bulk) of the grammar should be formally equivalent to the
current YACC grammar.300.  That would prove that the YACC and PEG parse
essentially the same language.  Given such a proof, is there any reason
why such a PEG would NOT be accepted as the new baseline grammar?

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