From: Heime <heimeborgia@protonmail.com>
To: tomas@tuxteam.de
Cc: help-gnu-emacs@gnu.org
Subject: Re: Calling a function with undefined symbol
Date: Mon, 31 Oct 2022 08:57:09 +0000 [thread overview]
Message-ID: <PnCdVt1Ag4FTqCRqp5zWYJ0pBsarv24b10GohZcTY0xQR3LgFk6gS2204qo4404P68dZa0G_P3LGgVIdB4jTvjpc4uBkGglHa3-3e10mObc=@protonmail.com> (raw)
In-Reply-To: <Y1+KjRmA1T0hdr68@tuxteam.de>
------- Original Message -------
On Monday, October 31st, 2022 at 8:42 AM, <tomas@tuxteam.de> wrote:
> On Mon, Oct 31, 2022 at 08:15:32AM +0000, Heime wrote:
>
> > Have written a function named "mbcomplt" that takes a symbol.
>
>
> The function takes an argument, that's what it does.
>
> > (defun mbcomplt (sgnl)
> > "DOC."
>
>
> sgnl here is a variable. Or a variable name. Depending on how
> you look at it.
>
> > (if (eq sgnl 'go)
> > (message "go")
> > (message "nogo")))
>
>
> Now you are comparing sgnl's /value/ to something (which happens
> to be a symbol).
>
> > I can call this function with
> >
> > (mbcomplt 'go)
>
>
> Yes. You could call it also with (mbcomplt 23). Or (mbcomplt "This is not a pipe").
> So?
>
> > This even though the symbol "'go" does not exist. What is happening here?
>
>
> As soon as you do 'go, the symbol exists.
>
> > My understanding about symbols is that I can make a symbol using
> >
> > (defvar seqr 3) ; set symbol seqr with value 3
>
>
> No, no. You are making a variable. Which is a binding of a symbol
> to a value.
Ok, I make a variable. What happens after that? A symbol 'seqr is made too?
> > (setq seqr 5) ; set symbol seqr with value 5
>
>
> No, you set the variable's value to 5. The symbol is not "set" to
> anything. It is an immutable thing, as far as Lisp is concerned.
Then, how is it that (symbol-value 'seqr) returns 5? There seems to be
a symbol and symbol-value returns 5.
> The symbol 'seqr is just taking the job of variable name here.
> Like you are called Heime (or whatever it is this week). That
> name is not you.
>
> > (symbol-value 'seqr) ; get value of symbol (returns 5)
> > (symbol-name 'seqr) ; get name of symbol (returns "seqr")
>
>
> Symbol-value returns the value associated to the symbol. The
> association itself is called a "variable".
>
> Please go re-read the manuals. You have got all of it confused :)
Yes, I have got really confused about what symbols are exactly. Even
after reading several times. I have never seen anybody make a symbol,
only variables. So, what is a symbol?
next prev parent reply other threads:[~2022-10-31 8:57 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-31 8:15 Calling a function with undefined symbol Heime
2022-10-31 8:32 ` Jean Abou Samra
2022-10-31 8:42 ` tomas
2022-10-31 8:57 ` Heime [this message]
2022-10-31 9:07 ` tomas
2022-10-31 9:24 ` Jean Abou Samra
2022-10-31 9:43 ` Heime
2022-10-31 9:58 ` Jean Abou Samra
2022-10-31 10:57 ` Heime
2022-10-31 17:00 ` [External] : " Drew Adams
2022-10-31 17:10 ` Emanuel Berg
2022-11-01 4:11 ` Drew Adams
2022-11-01 5:24 ` tomas
2022-11-01 15:58 ` Drew Adams
2022-11-01 16:13 ` tomas
2022-11-01 19:22 ` Drew Adams
2022-10-31 12:29 ` Stefan Monnier via Users list for the GNU Emacs text editor
2022-10-31 15:37 ` Emanuel Berg
2022-11-02 12:14 ` Michael Heerdegen
2022-11-02 14:25 ` Sam Steingold
2022-11-02 16:40 ` Michael Heerdegen
2022-11-02 17:28 ` Emanuel Berg
2022-11-02 23:04 ` Emanuel Berg
2022-11-03 11:09 ` Michael Heerdegen
2022-11-03 12:15 ` Emanuel Berg
2022-11-04 12:16 ` Michael Heerdegen
2022-11-05 14:32 ` Emanuel Berg
2022-11-05 23:22 ` Michael Heerdegen
2022-11-06 20:17 ` Emanuel Berg
2022-11-07 16:03 ` Michael Heerdegen
2022-11-07 16:50 ` [External] : " Drew Adams
2022-11-07 16:52 ` Emanuel Berg
2022-11-08 15:52 ` Michael Heerdegen
2022-11-08 19:15 ` tomas
2022-11-08 19:57 ` Michael Heerdegen
2022-11-08 20:47 ` tomas
2022-11-08 21:35 ` Sam Steingold
2022-11-08 23:53 ` Michael Heerdegen
2022-11-09 15:32 ` Sam Steingold
2022-11-09 15:59 ` Michael Heerdegen
2022-11-16 19:07 ` Emanuel Berg
2022-11-16 21:40 ` [External] : " Drew Adams
2022-11-16 21:55 ` Emanuel Berg
2022-11-04 14:33 ` Michael Heerdegen
2022-11-05 12:57 ` Emanuel Berg
2022-10-31 11:34 ` Emanuel Berg
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