From: Michael Heerdegen <michael_heerdegen@web.de>
To: help-gnu-emacs@gnu.org
Subject: Re: replacing a function with another one
Date: Thu, 13 Mar 2014 08:19:12 +0100 [thread overview]
Message-ID: <87siqmy39r.fsf@web.de> (raw)
In-Reply-To: 87vbvjmq0h.fsf@yun.yagibdah.de
lee <lee@yun.yagibdah.de> writes:
> So what is that supposed to mean? `let' keeps driving me insane already
> because it requires so many brackets. Then finally, I do something like
>
>
> (let ((end-marker (concat "^" comment-start lsl-hi-lock-patterns-end-marker))
> ((marker-pos (re-search-forward end-marker (point-max) t))))
> (do-stuff))
>
>
> and it doesn´t work because end-marker is undefined despite I just
> defined it :( So I have
>
>
> (let ((end-marker (concat "^" comment-start lsl-hi-lock-patterns-end-marker)))
> (let ((marker-pos (re-search-forward end-marker (point-max) t)))
> (do-something)))
>
The functionality you want, and that you reached with the nested `let',
is exactly what `let*' does. When I was learning LISP, I was also
confused about `let'. Standard `let' first evaluates all
expressions, then binds the variables, so in works "parallel" - see
(info "(elisp) Local Variables")
> And in the end, I´m left with the unanswerable question of how to
> intentionally returning something in particular from a function:
>
>
> (defun lsl-get-patterns-from-file (file)
> "Read hi-lock-mode highlighting-patterns from a file and return
> the patterns read."
> (with-current-buffer
> (find-file-noselect file)
> (goto-char (point-min))
> (let ((end-marker (concat "^" comment-start lsl-hi-lock-patterns-end-marker)))
> (let ((marker-pos (re-search-forward end-marker (point-max) t)))
> (when marker-pos
> (goto-char marker-pos)
> (previous-line)
> (end-of-line)
> (setq marker-pos (point))
> (goto-char (point-min))
> (message "reading hi-lock patterns from %s (%d..%d)"
> (buffer-name)
> (point-min) marker-pos)
> (let ((patterns nil))
> (while (< (point) marker-pos)
> (setq patterns (append (read (current-buffer)) patterns)))
> (setq patterns patterns)))))))
>
>
> I need this function to return `patterns'. Without the last line, it
> seems to return nil because the setq is enclosed in the while.
`let' returns the value returned by the last body expression (in
particular, that isn't necessarily the value of the variable `patterns'
in your example!). And `while' always returns nil (strictly speaking,
the return value isn't documented, so don't rely on it at all). So this
is what you want:
(let ((patterns nil))
(while (< (point) marker-pos)
(setq patterns (append (read (current-buffer)) patterns)))
patterns)
Michael.
next prev parent reply other threads:[~2014-03-13 7:19 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-08 19:43 replacing a function with another one lee
2014-03-08 19:54 ` Eli Zaretskii
2014-03-09 1:17 ` lee
2014-03-08 22:30 ` Michael Heerdegen
2014-03-09 17:58 ` lee
2014-03-09 19:10 ` Michael Heerdegen
2014-03-09 20:57 ` lee
2014-03-09 22:02 ` Michael Heerdegen
2014-03-10 0:53 ` lee
2014-03-10 2:18 ` Michael Heerdegen
2014-03-10 15:29 ` lee
2014-03-11 0:03 ` Michael Heerdegen
2014-03-11 13:34 ` lee
2014-03-11 23:40 ` Michael Heerdegen
2014-03-12 6:11 ` Michael Heerdegen
2014-03-12 7:07 ` Michael Heerdegen
2014-03-12 14:48 ` lee
2014-03-13 7:19 ` Michael Heerdegen [this message]
2014-03-15 19:51 ` lee
2014-03-17 12:00 ` Michael Heerdegen
2014-03-12 14:04 ` lee
2014-03-12 18:26 ` Stefan Monnier
2014-03-12 4:10 ` Michael Heerdegen
2014-03-10 12:44 ` Stefan Monnier
2014-03-10 23:35 ` lee
2014-03-11 0:41 ` Michael Heerdegen
2014-03-11 1:45 ` Michael Heerdegen
2014-03-11 19:05 ` lee
2014-03-11 22:58 ` Michael Heerdegen
2014-03-12 15:11 ` lee
2014-03-12 18:15 ` Stefan Monnier
2014-03-12 21:43 ` lee
2014-03-13 7:22 ` Michael Heerdegen
2014-03-15 20:02 ` lee
2014-03-11 4:11 ` lee
2014-03-11 5:01 ` Michael Heerdegen
2014-03-11 14:25 ` lee
2014-03-11 23:51 ` Michael Heerdegen
2014-03-12 15:22 ` lee
2014-03-13 7:33 ` Michael Heerdegen
2014-03-13 12:29 ` Stefan Monnier
2014-03-15 20:05 ` lee
2014-03-16 17:20 ` Stefan
2014-03-11 6:51 ` Michael Heerdegen
2014-03-11 15:41 ` lee
2014-03-11 23:21 ` Michael Heerdegen
2014-03-12 17:33 ` lee
2014-03-12 19:34 ` Florian Beck
2014-03-12 19:51 ` Florian Beck
2014-03-13 7:54 ` Michael Heerdegen
2014-03-15 20:14 ` lee
2014-03-12 12:45 ` Stefan Monnier
2014-03-12 17:42 ` lee
2014-03-13 2:43 ` Jambunathan K
2014-03-15 20:17 ` How to propose an emacs patch (Re: replacing a function with another one) lee
2014-03-16 3:21 ` Jambunathan K
2014-03-17 4:35 ` lee
2014-03-10 13:45 ` replacing a function with another one lee
2014-03-10 23:31 ` Michael Heerdegen
2014-03-12 13:16 ` Jambunathan K
2014-03-12 13:18 ` Jambunathan K
2014-03-15 20:22 ` lee
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