From: "Andreas Röhler" <andreas.roehler@easy-emacs.de>
To: Joost Kremers <joostkremers@fastmail.fm>
Cc: Help Gnu Emacs mailing list <help-gnu-emacs@gnu.org>
Subject: Re: pcase and minus-sign
Date: Wed, 30 Nov 2016 14:30:11 +0100 [thread overview]
Message-ID: <ae445475-96bc-fcd8-0a51-0b2236eb896a@easy-emacs.de> (raw)
In-Reply-To: <87r35tb0se.fsf@fastmail.fm>
On 30.11.2016 13:38, Joost Kremers wrote:
>
> On Wed, Nov 30 2016, Andreas Röhler wrote:
>> Hi,
>>
>> see code below. With numerical argument "1", first pattern is matched
>> as expected.
>>
>> However without arg the minus is matched - the second pattern, not
>> the default "_" at last.
>>
>> Any explanation?
>>
>> (defun foo (arg)
>> (interactive "P")
>> (pcase arg
>> (1 (message "%s" "ARG was `1'"))
>> (- (message "%s" "ARG was minus-sign"))
>> (_ (message "%s" "ARG not minus-sign"))))
>
> Probably because - is a symbol and hence a variable. It works if you
> quote it:
>
> (defun foo (arg)
> (interactive "P")
> (pcase arg
> (1 (message "%s" "ARG was `1'"))
> ('- (message "%s" "ARG was minus-sign"))
> (_ (message "%s" "ARG not minus-sign"))))
>
>
>
Thanks, that helps. Seems it relates to the following in docstring:
SYMBOL matches anything and binds it to SYMBOL.
Now if I use some arbitrary char, like "a",
(defun foo (arg)
(interactive "P")
(pcase arg
(a (message "%s" "ARG was `a'"))
(1 (message "%s" "ARG was `1'"))
('- (message "%s" "ARG was minus-sign"))
(_ (message "%s" "ARG not minus-sign"))))
It picks that a-branch at any case - as documented but strange.
next prev parent reply other threads:[~2016-11-30 13:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-30 12:12 pcase and minus-sign Andreas Röhler
2016-11-30 12:38 ` Joost Kremers
2016-11-30 13:30 ` Andreas Röhler [this message]
2016-11-30 13:31 ` Michael Heerdegen
2016-11-30 13:39 ` tomas
2016-11-30 13:56 ` Joost Kremers
2016-11-30 15:23 ` Andreas Röhler
2016-11-30 15:34 ` Michael Heerdegen
2016-11-30 15:48 ` Joost Kremers
2016-12-01 13:59 ` Andreas Röhler
2016-12-02 2:30 ` Stefan Monnier
2016-12-03 8:04 ` Andreas Röhler
2016-12-03 15:43 ` Stefan Monnier
2016-12-05 9:11 ` Andreas Röhler
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