Re: Advice on writing predicates

[Daniel Pittman <daniel@rimspace.net>]

Sarir Khamsi <sarir.khamsi@raytheon.com> writes:

> 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))

(defun dp/emacs-version-greater-than-23-p ()
  "REVISIT: Document me, you fool!"
  (interactive)
  (> (string-to-number (car (split-string emacs-version "\\."))) 23))

That does two things better: first, it uses the emacs-version variable which
just holds the version number.

Second, it doesn't bother with a specific true value, just a generic one,
which the '>' function happily returns.

Regards,
        Daniel