From: Anselm Helbig <anselm.helbig+news2009@googlemail.com>
To: help-gnu-emacs@gnu.org
Subject: Re: Advice on writing predicates
Date: Fri, 26 Jun 2009 01:23:56 +0200 [thread overview]
Message-ID: <87bpobgann.wl%anselm.helbig+news2009@googlemail.com> (raw)
In-Reply-To: <uhby454qg.fsf@raytheon.com>
At Thu, 25 Jun 2009 15:27:19 -0700,
Sarir Khamsi <sarir.khamsi@raytheon.com> wrote:
>
> I wrote a simple predicate that returns t if the Emacs major version
> number is greater than 22 and would like some advice/comments:
>
> The following
>
> (defun sk-emacs-version-greater-than23-p ()
> "Return non-nil if current Emacs version is greater than 22."
> (interactive)
> (setq version-string (replace-regexp-in-string ".*?\\([0-9]+\\)\.\\([0-9]+\\)\.\\([0-9]+\\)[()-.a-zA-Z0-9 \n]+" "\\1 \\2 \\3" (emacs-version)))
> (setq version-num (mapcar 'string-to-number (split-string version-string)))
> (if (> 22 (car version-num))
> t
> nil))
I hope you're not too disappointed, but there's a constant named
emacs-major-version:
(> emacs-major-version 22)
This is also extracted from the string in emacs-version, this is how
the emacs devs did it:
(defconst emacs-major-version
(progn (string-match "^[0-9]+" emacs-version)
(string-to-number (match-string 0 emacs-version)))
"Major version number of this version of Emacs.
This variable first existed in version 19.23.")
If you want to parse the version number yourself, this is how I would
do it:
(mapcar 'string-to-number (split-string emacs-version "\\."))
Note that the emacs-version variable just holds the number. This makes
things a lot easier.
Generally you shouldnt rely on the version number to test if a feature
is available - just test directly for the feature you need.
Regards,
Anselm
--
Anselm Helbig
mailto:anselm.helbig+news2009@googlemail.com
next prev parent reply other threads:[~2009-06-25 23:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-25 22:27 Advice on writing predicates Sarir Khamsi
2009-06-25 23:23 ` Anselm Helbig [this message]
2009-06-29 19:18 ` chickenphat
2009-06-26 6:40 ` Daniel Pittman
2009-06-26 7:37 ` Andreas Röhler
2009-06-26 9:13 ` Pascal J. Bourguignon
2009-06-26 11:02 ` Thien-Thi Nguyen
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