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Re: [fyi] extensible syntax, syntax features, parsing risk

From: John Kitchin
Subject: Re: [fyi] extensible syntax, syntax features, parsing risk
Date: Sat, 4 Dec 2021 18:52:13 -0500

Is it related to https://lists.gnu.org/archive/html/emacs-orgmode/2010-08/msg00404.html

I implemented that idea for fun once: https://kitchingroup.cheme.cmu.edu/blog/2015/02/05/Extending-the-org-mode-link-syntax-with-attributes/


Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213

On Sat, Dec 4, 2021 at 5:10 PM Samuel Wales <samologist@gmail.com> wrote:
the quoted post below, which had message id
20524da70901041233g105f372fv175a47dc9884fa43@mail.gmail.com , starts a
thread relevant to the current discussion of syntax, at least
historically, maybe practically.  could not find it online.

there were succeeding threads with examples and other stuff for id
markers and graph-theoretic things and other examples, where you as
user could always use a cl-like syntax [i.e. something like
"$[functionality-name arg :keyword arg]"].  my main concern was the
proliferation of syntax, and the risks of that [e.g. parsing] and
wanting the ability of factoring of syntax features.

display, parsing and so on would be shared [factored] among all the
different such features; org would always handle that the same.  thus
as a user even, you could add some new feature in lisp, and write it
in org using this syntax.  it would already work.

i have more in notes.  idk if it is still relevant, but i have
included the thread starter for the earliest thread [carsten/myself].

On 1/4/09, Samuel Wales <samologist@gmail.com> wrote:
> A general idea, which might or might not be useful.
> There are occasionally questions about syntax, like this:
>   Also, I'm afraid definition matching regexp won't play
>   nicely with text indentation, ... -- Paul
> Or this:
>   What would be safer?  -- Carsten
> I like the footnote implementation, so this is for future
> features, not necessarily footnotes.
> One issue when implementing new syntax (or changing existing
> syntax or cleaning up code) is parsing risk, which I will
> define as the risk that the syntax and the regexp or
> matching code:
>   1) conflicts with user text
>   2) conflicts with existing features
>   3) will be hard to maintain
>   4) constrains future features by making them conflict
>      syntactically
>   5) makes you run out of syntax to use in the future
>   6) will require complicated regexps
>   7) doesn't readily handle stuff you might want in the
>      future, like being combined with another feature
>   8) will be hard to quote, escape, comment, *boldify*, etc.
>   9) doesn't handle nestability, print-readability,
>      pretty-printability, syntax coloring, etc.
>   10) will be inefficient when called in a loop
>   11) isn't factored out
>   12) etc.
> For example, one of the many reasons for using org-IDs (:))
> in the conversation manager (as proposed) is that there are
> already functions to parse org-IDs, so a new syntax is not
> necessary and therefore parsing risk is minimized.
> In case parsing risk is a concern when adding a new feature
> to org, here is one idea: have a generic syntax that is
> extensible with keywords.
> The idea is to have a bracketing syntax with a reserved
> keyword as the first element that says what you are doing.
> To use footnotes as an example (this is not a suggestion to
> change footnote syntax, just an example that can be used for
> future syntax):
> You might use something like "here is some text to be
> footnoted $[fn apple]" to specify the footnote link, and
> "$[fn-target apples are delicious]" to specify the target.
> The general point I want to make is that once such a syntax
> is decided on, many future features are possible without
> introducing parsing risk.
> For example, you can implement a new feature as
> "$[my-new-feature ...]".  Then there is no parsing risk,
> even though you have just added a new feature.
> For modifications of features, you can use keywords:
> "$[my-new-feature ... :myparameter ...]".  These are easily
> parsed by standard functions for parsing lists.
> You can develop ways to boldify, quote, nest, prettily
> print, etc. this syntax, and those ways will work well with
> all future features that use it.
> Of course, the dollar sign and brackets are not the only
> possibility; it could be percent sign and parentheses, for
> example.
> You will not be starting from scratch.  Lisp has already
> worked out many of these issues.
> I will leave it to those who write massive amounts of org
> code to decide whether an extensible syntax might be useful
> to reduce parsing risk for future features.
> But I thought that I would propose the idea in case it is of
> interest.
> --
> For personal gain, myalgic encephalomyelitis denialists are knowingly
> causing further suffering and death by grossly corrupting science.  Do
> you care about the world?
> http://www.meactionuk.org.uk/What_Is_ME_What_Is_CFS.htm

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