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From: Michael Heerdegen <michael_heerdegen@web.de>
To: help-gnu-emacs@gnu.org
Subject: Re: Calling a function with undefined symbol
Date: Fri, 04 Nov 2022 13:16:33 +0100	[thread overview]
Message-ID: <87tu3egbj2.fsf@web.de> (raw)
In-Reply-To: 87o7toi68e.fsf@dataswamp.org

Emanuel Berg <incal@dataswamp.org> writes:

> >> Yes, but why do you need the "strange value" for that?

Let's call the strange `'''''''''...` values "quote-quine" for now so
that it's easier to talk about them (better than saying "the strange
value" all the time).  I said value_s_ here because there is no unique
quote-quine in the `eq' sense.

> > I chose it because you get an `equal' value when you quote
> > the value (to suggest a wrong track to an answer), and
>
> You do?
>
> (setq print-circle t)
>
> (setq x #1=(quote #1#))
>
> (eq    'x x) ; nil
> (equal 'x x) ; nil
>
> ?

I don't see any place in your code where a quote-quine is quoted.  You
correctly assign a quote-quine to a variable.  But then you only quote
the symbol, not the value, and compare the quote-quine with the symbol
you had bound it to.

IOW: It's a trap!

So how could a correct `equal'ity test of a quote-quine and that
quote-quine quoted be achieved?  This is exercise number 3.


> So the length is 2, but the depth is infinite. IOW: It's a trap!

Yes, this is the correct solution.  Congratulations!

Michael.




  reply	other threads:[~2022-11-04 12:16 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
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 [this message]
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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