From: pjb@informatimago.com (Pascal J. Bourguignon)
To: help-gnu-emacs@gnu.org
Subject: Re: Redefining functions and variables
Date: Thu, 29 Jul 2010 12:03:28 +0200 [thread overview]
Message-ID: <877hkeiozz.fsf@kuiper.lan.informatimago.com> (raw)
In-Reply-To: 08217e84-b4a0-4dd0-afbf-abd4d762c759@w30g2000yqw.googlegroups.com
Elena <egarrulo@gmail.com> writes:
> My modified macro is below. Why ',name is expanded as ... (as shown by
> `macroexpand-all'?
>
> (defvar old-defun 'defun) ; the symbol!
> (unintern 'defun)
>
> (defmacro defun (name args &rest body)
> `(progn
> ;; `load-file-name' is not null only if we are loading a
> file.
> (when (and load-file-name
> (fboundp ',name))
> (message "Warning: %s is being redefined in %s."
> (symbol-name ',name)
> load-file-name)
> (,old-defun ,name ,args
> ,@body))))
It is not.
(macroexpand '(defun. test (a) (+ 1 a)))
;; --> (progn (when (and load-file-name (fboundp (quote test))) (message "Warning: %s is being redefined in %s." (symbol-name (quote test)) load-file-name) (defun test (a) (+ 1 a))))
the "..." are only used to display the list when print-length or
eval-expression-print-length are not nil. See also print-level and
eval-expression-print-level.
%s can format symbols too:
(format ">> %s <<" 'example)
;; --> ">> example <<"
And you had your the old defun inside the when!
(defmacro defun (name args &rest body)
`(progn
;; `load-file-name' is not null only if we are loading a file.
(when (and load-file-name (fboundp ',name))
(message "Warning: %s is being redefined in %s." ',name load-file-name))
(,old-defun ,name ,args ,@body)))
Note: while name is known at macroexpansion time, you should refrain
to insert it in the string like this:
(message ,(format "Warning: %s is being redefined in %%s." name) load-file-name)
since name could contain percents and then you'd have build a wrong
format string for message. If you want to do that, you must escape
the percents:
(message ,(format "Warning: %s is being redefined in %%s."
(escape-percent name))
load-file-name)
with:
(defun escape-percent (string-designator)
(let ((string (etypecase string-designator
(string string-designator)
(symbol (symbol-name string-designator))
(character (string string-designator)))))
(unsplit-string (split-string string "%" nil) "%%")))
(defun unsplit-string (string-list &rest separator)
"Does the inverse than split-string. If no separator is provided
then a simple space is used."
(if (null separator)
(setq separator " ")
(if (= 1 (length separator))
(setq separator (car separator))
(error "unsplit-string: Too many separator arguments.")))
(if (not (char-or-string-p separator))
(error "unsplit-string: separator must be a string or a char."))
(apply 'concat (list-insert-separator string-list separator)))
(mapcar 'escape-percent '("abc" abc % %make- make-10%-of-profit %%internal%%))
;; --> ("abc" "abc" "%%" "%%make-" "make-10%%-of-profit" "%%%%internal%%%%")
--
__Pascal Bourguignon__ http://www.informatimago.com/
next prev parent reply other threads:[~2010-07-29 10:03 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-27 15:12 Redefining functions and variables Elena
2010-07-27 20:21 ` Stefan Monnier
2010-07-27 22:16 ` Elena
2010-07-28 0:35 ` Andreas Politz
2010-07-28 7:51 ` Elena
2010-07-28 14:29 ` Elena
2010-07-28 18:48 ` Andreas Politz
2010-07-28 20:37 ` Pascal J. Bourguignon
2010-07-29 8:32 ` Elena
2010-07-29 9:57 ` Stefan Monnier
2010-07-29 10:16 ` Elena
2010-07-29 13:14 ` Stefan Monnier
2010-07-30 19:32 ` Uday S Reddy
2010-07-29 10:31 ` Andreas Politz
2010-07-29 11:46 ` Johan Bockgård
2010-07-29 15:54 ` Andreas Politz
2010-07-29 12:41 ` Tim X
2010-07-29 10:03 ` Pascal J. Bourguignon [this message]
2010-07-29 10:28 ` Elena
2010-07-29 20:35 ` Johan Bockgård
2010-07-29 22:22 ` Tim X
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