emacs-orgmode@gnu.org archives
 help / color / mirror / code / Atom feed
From: Ken Mankoff <mankoff@gmail.com>
To: Nicolas Goaziou <mail@nicolasgoaziou.fr>
Cc: Bastien <bzg@gnu.org>, "Przemysław Kamiński" <pk@intrepidus.pl>,
	emacs-orgmode@gnu.org
Subject: Re: official orgmode parser
Date: Mon, 26 Oct 2020 09:17:16 -0700	[thread overview]
Message-ID: <87r1plj71v.fsf@gmail.com> (raw)
In-Reply-To: <87sga13w62.fsf@nicolasgoaziou.fr>

[-- Attachment #1: Type: text/plain, Size: 1889 bytes --]


On 2020-10-26 at 07:21 -07, Nicolas Goaziou <mail@nicolasgoaziou.fr> wrote...
> Ken Mankoff <mankoff@gmail.com> writes:
>
>> I question if this is possible because EBNF is for context-free
>> grammars, but I *think* Org syntax is context-free.
>
> It's not as explained in a footnote in the Org syntax document.

Yes, I meant to write that I think Org syntax is maybe *not* context-free, and therefore EBNF can't capture all of it. But it could still be very helpful and capture most of it.

But the more I think about it, the more I think Org may be context-free.

For the footnotes, I'm not sure that "(1) In particular, the parser requires stars at column 0 to be quoted by a comma when they do not define a headline" violates context. An "*" in the first column defines a header. It can be escaped by anything else too (" *" works too). If ",*" has a special meaning, that can be captured elsewhere in the syntax.

I'm also not sure (2) violates context-freeness, at least in the EBNF sense where a context can include a newline. See for example:

section ::= "*"+ string (tag+) newline (planning newline)? (property_drawer newline)?

planning ::= ("SCHEDULED:" "<" date_or_time ">")? ("DEADLINE:" "<" date_or_time ">")?

property_drawer ::= ":PROPERTIES:" newline drawer_contents newline ":END:"

drawer_contents ::= ":" property ":" whitespace string

Where the first line, "section" is represented graphically as the attached image.

I guess I'm not 100% clear what "context-free" means. EBNF can represent a language where a for loop has an opening and closing brace. The closing brace is context-dependent, just as the planning or property drawers are.

I recently used EBNF to represent a CSV file with header, and I was unable to capture the requirement that the header column must have the same number of fields or commas as the data section. I think that is context-free. 



[-- Attachment #2: tmp_20201026_090940.png --]
[-- Type: image/png, Size: 8197 bytes --]

[-- Attachment #3: Type: text/plain, Size: 7 bytes --]


  -k.

  reply	other threads:[~2020-10-26 16:20 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-15  7:58 Przemysław Kamiński
2020-09-15  8:44 ` Gerry Agbobada
2020-09-16 16:36   ` Matt Huszagh
2020-09-23  8:09   ` Bastien
2020-09-15  9:03 ` Tim Cross
2020-09-15  9:17   ` Przemysław Kamiński
2020-09-15  9:55     ` Russell Adams
2020-09-15 11:15       ` Przemysław Kamiński
2020-09-15 12:37         ` tomas
2020-09-15 18:09           ` Diego Zamboni
2020-09-16 12:09           ` Przemysław Kamiński
2020-09-16 12:20             ` tomas
2020-09-16 12:27             ` Ihor Radchenko
2020-09-16  0:16     ` Tim Cross
2020-09-16  7:24     ` Marcin Borkowski
2020-09-16  7:56       ` Ihor Radchenko
2020-09-16 11:36         ` Przemysław Kamiński
2020-09-16 12:02           ` Ihor Radchenko
2020-09-16 12:15             ` Przemysław Kamiński
2020-09-17  1:18               ` Ihor Radchenko
2020-09-17 15:24                 ` Przemysław Kamiński
2020-09-23  8:09 ` Bastien
2020-09-23 17:46   ` Przemysław Kamiński
2020-09-23 19:50     ` rey-coyrehourcq
2020-11-11  8:58       ` Bastien
2020-10-24 21:12   ` Daniele Nicolodi
2020-10-24 21:35     ` Tom Gillespie
2020-11-11  9:13       ` Bastien
2020-11-12 17:14         ` Tom Gillespie
2020-11-11  9:15     ` Bastien
2020-11-11 13:05       ` Daniele Nicolodi
2020-11-28 19:19       ` Gerry Agbobada
2020-10-26 11:23   ` Ken Mankoff
2020-10-26 14:21     ` Nicolas Goaziou
2020-10-26 16:17       ` Ken Mankoff [this message]
2020-10-26 16:24         ` Nicolas Goaziou
2020-10-26 16:47           ` Ken Mankoff
2020-10-26 17:59             ` Tom Gillespie
2020-10-26 20:26               ` Ken Mankoff
2020-10-26 21:00                 ` Tom Gillespie
2020-10-26 21:37                   ` Ken Mankoff
2020-10-26 22:19                     ` Tom Gillespie
2020-10-27  5:42                   ` Przemysław Kamiński
2020-11-11  8:59             ` Bastien
2020-11-11  9:00         ` Bastien

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://www.orgmode.org/

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87r1plj71v.fsf@gmail.com \
    --to=mankoff@gmail.com \
    --cc=bzg@gnu.org \
    --cc=emacs-orgmode@gnu.org \
    --cc=mail@nicolasgoaziou.fr \
    --cc=pk@intrepidus.pl \
    --subject='Re: official orgmode parser' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Code repositories for project(s) associated with this inbox:

	https://git.savannah.gnu.org/cgit/emacs/org-mode.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).