From jcowan@reutershealth.com Mon Feb  9 11:52:58 2004
Return-path: <jcowan@reutershealth.com>
Envelope-to: rlpowell@digitalkingdom.org
Delivery-date: Mon, 09 Feb 2004 11:52:58 -0800
Received: from [65.246.141.36] (helo=mail.reutershealth.com)
	by chain.digitalkingdom.org with esmtp (Exim 4.30)
	id 1AqHSk-0002KO-O2
	for rlpowell@digitalkingdom.org; Mon, 09 Feb 2004 11:52:58 -0800
Received: from skunk.reutershealth.com (mail [65.246.141.36])
	by mail.reutershealth.com (Pro-8.9.3/Pro-8.9.3) with SMTP id OAA14234
	for <rlpowell@digitalkingdom.org>; Mon, 9 Feb 2004 14:47:09 -0500 (EST)
Received: by skunk.reutershealth.com (sSMTP sendmail emulation); Mon,  9 Feb 2004 14:52:51 -0500
Date: Mon, 9 Feb 2004 14:52:51 -0500
From: jcowan@reutershealth.com
To: Robin Lee Powell <rlpowell@digitalkingdom.org>
Subject: Re: BNF rule 10?
Message-ID: <20040209195251.GC3152@skunk.reutershealth.com>
References: <20040209190546.GC1600@digitalkingdom.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20040209190546.GC1600@digitalkingdom.org>
User-Agent: Mutt/1.4.1i
X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on 
	chain.digitalkingdom.org
X-Spam-Level: 
X-Spam-Status: No, hits=-4.7 required=5.0 tests=BAYES_00,NO_REAL_NAME 
	autolearn=no version=2.63
Status: RO
X-Status: A
Content-Length: 843
Lines: 23

Robin Lee Powell scripsit:
> Hey, John.
> 
> Looking at the BNF grammar, was hoping you could give a formalized
> explanation of:
> 
>     10) // encloses an elidable terminator, which may be omitted
>     (without change of meaning) if no grammatical ambiguity results.
> 
> I assume this is different then merely making something optional?

An elidable terminator is, strictly speaking, only optional if all other
elidable terminators at that point are apparent.  If I write

	le nu broda /kei/ /ku/ brode

then I can leave out kei or ku but not both.

-- 
Even a refrigerator can conform to the XML      John Cowan
Infoset, as long as it has a door sticker       jcowan@reutershealth.com
saying "No information items inside".           http://www.reutershealth.com
        --Eve Maler                             http://www.ccil.org/~cowan

From jkominek@miranda.org Mon Feb  9 12:08:46 2004
Return-path: <jkominek@miranda.org>
Envelope-to: rlpowell@digitalkingdom.org
Delivery-date: Mon, 09 Feb 2004 12:08:46 -0800
Received: from miranda.org ([209.58.150.153] ident=qmailr)
	by chain.digitalkingdom.org with smtp (Exim 4.30)
	id 1AqHi2-0002Z4-9p
	for rlpowell@digitalkingdom.org; Mon, 09 Feb 2004 12:08:46 -0800
Received: (qmail 16212 invoked by uid 534); 9 Feb 2004 20:08:44 -0000
From: jkominek@miranda.org
Date: Mon, 9 Feb 2004 13:08:44 -0700
To: Robin Lee Powell <rlpowell@digitalkingdom.org>
Cc: jcowan@reutershealth.com
Subject: Re: BNF rule 10?
Message-ID: <20040209200844.GK30563@miranda.org>
References: <20040209190546.GC1600@digitalkingdom.org> <20040209195251.GC3152@skunk.reutershealth.com> <20040209200518.GA8463@digitalkingdom.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20040209200518.GA8463@digitalkingdom.org>
User-Agent: Mutt/1.3.28i
Accept-Language: jbo, en
X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on 
	chain.digitalkingdom.org
X-Spam-Level: 
X-Spam-Status: No, hits=-4.8 required=5.0 tests=AWL,BAYES_00,NO_REAL_NAME 
	autolearn=no version=2.63
Status: RO
X-Status: A
Content-Length: 497
Lines: 12

On Mon, Feb 09, 2004 at 12:05:18PM -0800, Robin Lee Powell wrote:
> But from that point I'm stuck with what to do with the stuff in //s.
> Jay says that you just make one rule with the option and one without
> (i.e. that they're the same as []), which makes sense to me but I
> thought I'd check with you.

I'd like to mention that I put a number of caveats on that.

-- 
Jay Kominek <jkominek@miranda.org>
Genius may have its limitations, but stupidity
is not thus handicapped. -- Elbert Hubbard

From jcowan@reutershealth.com Mon Feb  9 12:19:48 2004
Return-path: <jcowan@reutershealth.com>
Envelope-to: rlpowell@digitalkingdom.org
Delivery-date: Mon, 09 Feb 2004 12:19:48 -0800
Received: from [65.246.141.36] (helo=mail.reutershealth.com)
	by chain.digitalkingdom.org with esmtp (Exim 4.30)
	id 1AqHsi-0002cZ-L9
	for rlpowell@digitalkingdom.org; Mon, 09 Feb 2004 12:19:48 -0800
Received: from skunk.reutershealth.com (mail [65.246.141.36])
	by mail.reutershealth.com (Pro-8.9.3/Pro-8.9.3) with SMTP id PAA14550
	for <rlpowell@digitalkingdom.org>; Mon, 9 Feb 2004 15:14:02 -0500 (EST)
Received: by skunk.reutershealth.com (sSMTP sendmail emulation); Mon,  9 Feb 2004 15:19:46 -0500
Date: Mon, 9 Feb 2004 15:19:46 -0500
From: jcowan@reutershealth.com
To: Robin Lee Powell <rlpowell@digitalkingdom.org>
Subject: Re: BNF rule 10?
Message-ID: <20040209201946.GE3152@skunk.reutershealth.com>
References: <20040209190546.GC1600@digitalkingdom.org> <20040209195251.GC3152@skunk.reutershealth.com> <20040209200518.GA8463@digitalkingdom.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20040209200518.GA8463@digitalkingdom.org>
User-Agent: Mutt/1.4.1i
X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on 
	chain.digitalkingdom.org
X-Spam-Level: 
X-Spam-Status: No, hits=-4.7 required=5.0 tests=BAYES_00,NO_REAL_NAME 
	autolearn=no version=2.63
Status: RO
X-Status: A
Content-Length: 1506
Lines: 35

Robin Lee Powell scripsit:

> But from that point I'm stuck with what to do with the stuff in //s.
> Jay says that you just make one rule with the option and one without
> (i.e. that they're the same as []), which makes sense to me but I
> thought I'd check with you.

You can't transform them into BNF at all, because the whole point
is that the behavior of /xxx/ is not context-free: you can't decide
whether a terminator is elidable without looking at the entire context.
Consider this simplified grammar:

	start = sumti selbri
	sumti = LE selbri /KU/
	selbri = tanru | NU tanru /KEI/
	tanru = BRIVLA | tanru BRIVLA

then "le nu broda ku brode" and "le nu broda kei brode" are grammatical,
but "le nu broda brode", eliding both terminators, is not.  But if we
rewrote the elidable terminators as optional elements, then "le nu broda
brode" would be grammatical and ambiguous.

The way the official parser implements elidable terminators is using
the yyerror routine: a terminator is a choice between the appropriate
selma'o and "error"; the error routine figures out which selma'o should
be present and inserts it into the token stream.  If it has a choice,
it chooses the innermost one, so "le nu broda brode" above would be
rewritten as "le nu broda brode kei ku" and blow up because there is
nothing to match the "selbri" rule.


-- 
John Cowan  <jcowan@reutershealth.com>  http://www.ccil.org/~cowan
        Raffiniert ist der Herrgott, aber boshaft ist er nicht.
                --Albert Einstein

From jcowan@reutershealth.com Tue Feb 10 14:24:43 2004
Return-path: <jcowan@reutershealth.com>
Envelope-to: rlpowell@digitalkingdom.org
Delivery-date: Tue, 10 Feb 2004 14:24:43 -0800
Received: from [65.246.141.36] (helo=mail.reutershealth.com)
	by chain.digitalkingdom.org with esmtp (Exim 4.30)
	id 1AqgJ9-0006Mw-3j
	for rlpowell@digitalkingdom.org; Tue, 10 Feb 2004 14:24:43 -0800
Received: from skunk.reutershealth.com (mail [65.246.141.36])
	by mail.reutershealth.com (Pro-8.9.3/Pro-8.9.3) with SMTP id RAA05500
	for <rlpowell@digitalkingdom.org>; Tue, 10 Feb 2004 17:18:54 -0500 (EST)
Received: by skunk.reutershealth.com (sSMTP sendmail emulation); Tue, 10 Feb 2004 17:24:35 -0500
Date: Tue, 10 Feb 2004 17:24:35 -0500
From: jcowan@reutershealth.com
To: Robin Lee Powell <rlpowell@digitalkingdom.org>
Subject: Re: JCBNF & operator
Message-ID: <20040210222435.GA2647@skunk.reutershealth.com>
References: <20040210220015.GX8463@digitalkingdom.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20040210220015.GX8463@digitalkingdom.org>
User-Agent: Mutt/1.4.1i
X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on 
	chain.digitalkingdom.org
X-Spam-Level: 
X-Spam-Status: No, hits=-4.7 required=5.0 tests=BAYES_00,NO_REAL_NAME 
	autolearn=no version=2.63
Status: RO
X-Status: A
Content-Length: 702
Lines: 19

Robin Lee Powell scripsit:

>     A & B & C == A [B] [C] | [A] B [C] | [A] [B] C

Yes.  Here's the proof for 3 arguments:

	A & B & C = A & (B & C)
		= A | (B & C) | A (B & C)
		= A | (B | C | B C) | A (B | C | B C)
		= A | B | C | B C | A B | A C | A B C

Mathematical induction tells us if it works for 3, it works for every case.

-- 
John Cowan  www.ccil.org/~cowan  www.reutershealth.com  jcowan@reutershealth.com
We want more school houses and less jails; more books and less arsenals;
more learning and less vice; more constant work and less crime; more
leisure and less greed; more justice and less revenge; in fact, more of
the opportunities to cultivate our better natures.  --Samuel Gompers

From jcowan@reutershealth.com Tue Feb 10 15:04:22 2004
Return-path: <jcowan@reutershealth.com>
Envelope-to: rlpowell@digitalkingdom.org
Delivery-date: Tue, 10 Feb 2004 15:04:22 -0800
Received: from [65.246.141.36] (helo=mail.reutershealth.com)
	by chain.digitalkingdom.org with esmtp (Exim 4.30)
	id 1AqgvW-0006wr-62
	for rlpowell@digitalkingdom.org; Tue, 10 Feb 2004 15:04:22 -0800
Received: from skunk.reutershealth.com (mail [65.246.141.36])
	by mail.reutershealth.com (Pro-8.9.3/Pro-8.9.3) with SMTP id RAA06197
	for <rlpowell@digitalkingdom.org>; Tue, 10 Feb 2004 17:58:35 -0500 (EST)
Received: by skunk.reutershealth.com (sSMTP sendmail emulation); Tue, 10 Feb 2004 18:02:22 -0500
Date: Tue, 10 Feb 2004 18:02:22 -0500
From: jcowan@reutershealth.com
To: Robin Lee Powell <rlpowell@digitalkingdom.org>
Subject: Re: JCBNF & operator
Message-ID: <20040210230222.GB2647@skunk.reutershealth.com>
References: <20040210220015.GX8463@digitalkingdom.org> <20040210222435.GA2647@skunk.reutershealth.com> <20040210223357.GZ8463@digitalkingdom.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20040210223357.GZ8463@digitalkingdom.org>
User-Agent: Mutt/1.4.1i
X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on 
	chain.digitalkingdom.org
X-Spam-Level: 
X-Spam-Status: No, hits=-4.7 required=5.0 tests=BAYES_00,NO_REAL_NAME 
	autolearn=no version=2.63
Status: RO
Content-Length: 670
Lines: 15

Robin Lee Powell scripsit:

> I've just finished turning bnf.300 into ABNF format, prepratory for
> Jay and I taking a hard look at the elidable terminators issue.  Do
> you mind if I post the discussion we've had thus far?

No problem.

-- 
They do not preach                              John Cowan
  that their God will rouse them                jcowan@reutershealth.com
    A little before the nuts work loose.        http://www.ccil.org/~cowan
They do not teach                               http://www.reutershealth.com
  that His Pity allows them                         --Rudyard Kipling,
    to drop their job when they damn-well choose.   "The Sons of Martha"

