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Re: Proper use of function form


From: Tim Johnson
Subject: Re: Proper use of function form
Date: Mon, 27 Apr 2020 11:12:22 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1


On 4/27/20 12:06 AM, Emanuel Berg via Users list for the GNU Emacs text editor wrote:
Tim Johnson wrote:

Here is a key definition:

(define-key jinja2-mode-map (kbd "C-c i") #'jinja2-insert-var)

As I understand it, the sharp-quote (#') tells the
compiler that jinja2-insert-var is meant to be
a function
Yes, that's what happens. I don't know what the
byte-compiler does with that information tho, maybe it
is just a matter of it being able to warn you if that
function doesn't exist, since with the hash-quote, it
knows where to look specifically...

But there is also the advantage of you being able to see
that something is, or supposed to be, a function.

Perhaps font-lock could also be told to give it
a special color, e.g. `font-lock-function-name-face', if
desired - to increase seeing/reduce reading
even further.

The following quotation:

"it is always good practice to sharp quote every
symbol that is the name of a function, whether it's
going into a mapcar, an apply, a funcall, or
anything else."
Well, that's what I do and it always worked. But if you
seek a more scientific documentation and practical
HOWTO, surely this is documented in the official
manual(s)?

(setq my-keypairs '("h" my-h-func "g" my-g-func "f" my-f-func))

and using iteration to *programmatically* call
define-key for multiple key definitions as in

(define-key mymap                          ;; add to keymap
     (kbd (concat ldr (nth ndx mylist)))    ;; sequence as in "g"
     (nth (+ ndx 1) mylist))                ;;
command as in my-g-func

The form above is indeed a snippet from a defun that
I have used for years

Would it be better to change (nth (+ ndx 1) mylist) to
(function (nth (+ ndx 1) mylist)) ?
But even if that had worked all the advantages mentioned
so far would be lost, right?

Maybe you could initially instead of the quote use the
backquote/comma, or `list', with hash-quote?

Thanks Emanuel. Of course you know that it was your use of the sharp-quote in a response to an earlier question by me that prompted me to ask this latter question. I will play around with with subsequent advice when I have the time.

cheers

--
Tim
tj49.com




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