Re: [elpa] externals/org 26ef5e3e5b: org-src: Use `sh-mode' for all the shells it can handle

[Philip Kaludercic]

Lynn Winebarger <owinebar@gmail.com> writes:

> On Mon, Apr 17, 2023, 12:10 PM Stefan Monnier <monnier@iro.umontreal.ca>
> wrote:
>
>> >  (defcustom org-src-lang-modes
>> > -  '(("C" . c)
>> > +  `(("C" . c)
>> >      ("C++" . c++)
>> >      ("asymptote" . asy)
>> > -    ("bash" . sh)
>> >      ("beamer" . latex)
>> >      ("calc" . fundamental)
>> >      ("cpp" . c++)
>> > @@ -208,9 +215,10 @@ but which mess up the display of a snippet in Org
>> exported files.")
>> >      ("elisp" . emacs-lisp)
>> >      ("ocaml" . tuareg)
>> >      ("screen" . shell-script)
>> > -    ("shell" . sh)
>> >      ("sqlite" . sql)
>> > -    ("toml" . conf-toml))
>> > +    ("toml" . conf-toml)
>> > +    ("shell" . sh)
>> > +    ,@(org-src--get-known-shells))
>> >    "Alist mapping languages to their major mode.
>>
>> Side note: while it really doesn't matter here for such trivial
>> top-level code, I prefer to put such ,@ at the beginning rather than the
>> end of lists, when it's an option.  Basically because it's more
>> efficient to add to the beginning rather than to the end of a list:
>>
>>     ELISP> (macroexpand '`(,@(list 1 2) a b c d))
>>     (append (list 1 2) '(a b c d))
>>     ELISP> (macroexpand '`(a b c d ,@(list 1 2)))
>>     (cons 'a (cons 'b (cons 'c (cons 'd (list 1 2)))))
>>     ELISP>

Is this just an implementation detail, or is there a reason that this
could not expand to 

  (append '(a b c d) (list 1 2))

> Why is the former more efficient than the latter?  It looks like the former
> would have to construct the '(1 2) list twice, and the latter only once.
> And the '(a b c d) cons cells are only allocated once either way.

(I believe) It is more efficient, since there are fewer function calls.
I have had issues in the past with ,@ expanding to code that would have
exceeded the maximal evaluation depth, until I split it up and manually
used `append' that has the advantage of being implemented in C.

> Lynn