[lojban] Re: gleki xisri'i

[Minimiscience <minimiscience@gmail.com>]

de'i li 25 pi'e 12 pi'e 2008 la'o fy. Robin Lee Powell .fy. cusku zoi
skamyxatra.
> We asked for a general CFG, not something that only works in some
> specific grammar generator.
.skamyxatra

When did you say that?  In your original e-mail
(<http://www.lojban.org/lists/lojban-beginners/msg06812.html>) you said, in
addition to the passage quoted earlier, "Produce a working CFG for Lojban, in
any format that some parser generator somewhere can accept...".  I don't see
any restriction to a general CFG anywhere in that thread.

> Furthermore, and this is much more important, unless I'm really
> missing something you're *changing the precedence as the grammar is
> parsed*.  That is, if a parse doesn't work without a particular
> terminator you drop the precedence of that terminator-free
> production to zero *at parse time*.  If that's reducable to a
> 4-tuple a la http://en.wikipedia.org/wiki/Context_free_grammar I'd
> be *really* surprised indeed!

That's not how it works.  If the parser must choose between reducing the
current construct and shifting the next terminal before reducing, it uses the
precedence rules to determine which action to take, and these precedence rules
are set in stone when Yacc parses its input.  In the case of the Lojban
grammar, if a construct can be terminated and the terminator is the next input
symbol, the terminator is shifted onto the stack, and then the entire construct
is reduced.  This takes place regardless of whether it leads to a valid parse
tree.  See <http://www.opengroup.org/onlinepubs/000095399/utilities/yacc.html
#tag_04_174_13_07> for more information.

I also feel it worth pointing out that since most implementations of Yacc
(including the ones I tested this with), when given the -v option, generate a
file describing every state of the parsing automaton for the given grammar in
all of its deterministic glory, any actions that the parser takes at runtime
must be foreseeable and have results that can be predetermined in a
context-free manner.

mu'omi'e la'o gy. Minimiscience .gy.

-- 
mi klama .i mi viska .i mi fanva fi la lojban.


To unsubscribe from this list, send mail to lojban-list-request@lojban.org
with the subject unsubscribe, or go to http://www.lojban.org/lsg2/, or if
you're really stuck, send mail to secretary@lojban.org for help.