From: "Pascal J. Bourguignon" <pjb@informatimago.com>
To: help-gnu-emacs@gnu.org
Subject: Re: elisp: can a function/defun return two strings..? prompt for two strings??
Date: Sun, 27 Feb 2011 12:07:48 +0100 [thread overview]
Message-ID: <87hbbp20sb.fsf@kuiper.lan.informatimago.com> (raw)
In-Reply-To: mailman.2.1298798656.16925.help-gnu-emacs@gnu.org
ken <gebser@mousecar.com> writes:
> In one line of a file/buffer (which might exist or might not) will be
> two strings, both of which must be fetched and returned to the calling
> function. I was going to write two separate functions, one for each
> string, but since both strings are in the same line, it seemed highly
> inefficient to search for the same line of text twice... made more sense
> to search for it once, and get both strings in the same function.
>
> Here's pseudo-code:
(defun pseudo-code ()
> ;; search buffer for line of interest.
(let ((line-of-interest (search-buffer-for-it)))
> ;; if the line exists
(if (line-exists-p line-of-interest)
(list
> ;; does it specify str1?
(if (line-specify-str1-p line-of-interest)
> ;; if it does, grab that str1, hold it for eventual return
(grab-str1 line-of-interest)
> ;; if it doesn't, prompt user for it, and hold it for eventual
> return.
(read-from-minibuffer "prompt for str1"))
> ;; does the same line specify str2?
(if (line-specify-str2-p line-of-interest)
> ;; if it does, grab that str2, hold it for eventual return
(grab-str2 line-of-interest)
> ;; if it doesn't, prompt user for it, and hold it for eventual
> return.
(read-from-minibuffer "prompt for str2")))
> ;; if the line doesn't exist,
> ;; prompt user for str1 and str2
(let ((str1 (read-from-minibuffer "prompt for str1"))
(str2 (read-from-minibuffer "prompt for str2")))
(insert "%s %s\n" str1 str2)
(list str1 str2)))))
> ;; create/insert new line in buffer, inserting str1 & str2 into it.
> ;; return str1 and str2 to calling function
Now you just need to implement the missing functions used above...
> Most of the coding for the above will busy itself with finding the line
> of interest-- or determining that it doesn't exist.
I doubt so. Clearly, the coding above busies itself with something
else, as the pseudo code clearly indicates.
> So why should I do
> that twice, once for each string? Sure, I could save to a variable the
> location of the line of interest to avoid having to search for it again,
> but then I'm back to working with two variables, the location and just
> one string. So that's a non-solution.
What are you talking about???
> So how to "return" two variables to a calling function, possibly have to
> prompt for one or both of them? (I can think of a half dozen ways to do
> this in C, but this is elisp.)
You cannot return variables, only values, resulting from the evaluation
of expressions.
--
__Pascal Bourguignon__ http://www.informatimago.com/
A bad day in () is better than a good day in {}.
next prev parent reply other threads:[~2011-02-27 11:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.2.1298798656.16925.help-gnu-emacs@gnu.org>
2011-02-27 10:31 ` elisp: can a function/defun return two strings..? prompt for two strings?? Harald Hanche-Olsen
2011-02-27 11:07 ` Pascal J. Bourguignon [this message]
2011-02-27 21:10 ` Tim X
2011-02-27 9:24 ken
2011-02-27 10:39 ` Andrea Crotti
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