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Re: master 305dbc7 2/4: Move description of value to syntax-ppss functio

From: Alan Mackenzie
Subject: Re: master 305dbc7 2/4: Move description of value to syntax-ppss function.
Date: Wed, 30 Oct 2019 20:34:21 +0000
User-agent: Mutt/1.10.1 (2018-07-13)

Hello, Lars.

On Wed, Oct 30, 2019 at 16:29:44 +0100, Lars Ingebrigtsen wrote:
> Lars Ingebrigtsen <address@hidden> writes:

> > So perhaps that patch should be reverted anyway.  Or have the list in
> > both functions.  Or, even better, stop saying

> > (if (nth 5 state)
> >     (do-something-incomprehensible)
> >   (do-something-else-incomprehensible))

> > everywhere and just add accessor functions already, so that the code
> > becomes marginally more readable.  Because trying to make sense of it
> > now is just too hard, and it doesn't have to be.

> If we want to do this, I volunteer to start doing the rewrite -- I have
> some functions for this from the decoded time makeover...

> So what would the accessor macros be?  Err...  looking at the doc
> string, something like:

> ppss-depth
> ppss-start-innermost
> ppss-start-last-complete-sexp
> ppss-string-terminator
> ppss-comment-nesting
> ppss-after-quote-character
> ppss-minimum-paren-depth
> ppss-comment-style
> ppss-start-comment-or-string
> ppss-open-paren-positions
> ppss-two-character-syntax
> ppss-internal

For a start, why the prefix "ppss-"?  The values are the results of
calling parse-partial-sexp (however indirectly), so "pps-" would be more
accurate, as well as being a character shorter.

But I'm thoroughly against this change.  It's bloat.  On a good day,

            (or (nth 3 s) (nth 4 s))

will easily fit onto a single line of code, often with room for a
comment such as "; in a string or comment.".

            (or (pps-string-terminator s) (pps-comment-nesting s))

is much less likely to do so.  So we end up with an extra line, whether
a continuation line added by redisplay, or a real extra line added by
the hacker.  In either case this is undesirable.

I doubt these macros will be easier to read than the use of nth.  They
are too long to be instantly recognised - the eye and the brain must
scan them piece by piece.  (nth 3 s) can be a mental atom, requiring no

In practice, by far most of the accesses to the state returned by
parse-partial-sexp are elements 3, 4, and 8, so anybody using
parse-partial-sexp quickly learns what these mean.  Others can be
explained by comments, if needed.  Anybody who doesn't recognise elts 3,
4, and 8 is probably best advised to read the pertinent manual page

These new macro names would be a burden to learn and use, and a burden
on the Emacs Lisp manual.

Please don't do this.

> -- 
> (domestic pets only, the antidote for overdose, milk.)
>    bloggy blog: http://lars.ingebrigtsen.no

Alan Mackenzie (Nuremberg, Germany).

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