From: Helmut Eller <eller.helmut@gmail.com>
To: help-gnu-emacs@gnu.org
Subject: Re: Replacement for Common Lisp's GENSYM in Emacs Lisp
Date: Sun, 07 Mar 2010 23:07:16 +0100 [thread overview]
Message-ID: <m28wa3pyzv.fsf@gmail.com> (raw)
In-Reply-To: jwv4oksm005.fsf-monnier+gnu.emacs.help@gnu.org
* Stefan Monnier [2010-03-07 20:06+0100] writes:
>> This is actually a non-trivial problem. Best approach would probably be
>> to do something similar to how they generate universally unique IDs.
>
> The best approach often is to not use "unique symbols" at all. A common
> technique is to rely on lexical scoping to precisely control which
> variables are visible to each part of a macro's argument during its
> evaluation. E.g.:
>
> (defmacro dotimes (xl e)
> (let ((x (car xl))
> (l (cadr xl)))
> `(let ((body (lambda (,x) ,e))
> (list ,l))
> (while (consp list)
> (funcall body (car list))
> (setq list (cdr list))))))
>
> Notice how the expressions `l' and `e' are evaluated in a context where
> neither of `body', nor `list' exist. No need for gensym.
What makes you think that body and list aren't bound in e?
Helmut
next prev parent reply other threads:[~2010-03-07 22:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.2359.1267888813.14305.help-gnu-emacs@gnu.org>
2010-03-06 16:10 ` Replacement for Common Lisp's GENSYM in Emacs Lisp David Kastrup
2010-03-06 16:35 ` Teemu Likonen
2010-03-07 7:07 ` Tim X
2010-03-07 19:06 ` Stefan Monnier
2010-03-07 22:07 ` Helmut Eller [this message]
2010-03-08 4:55 ` Stefan Monnier
2010-03-08 7:01 ` Helmut Eller
2010-03-09 2:33 ` Stefan Monnier
2010-03-06 15:19 Teemu Likonen
2010-03-07 5:48 ` tomas
2010-03-07 6:13 ` Teemu Likonen
[not found] ` <mailman.2390.1267942438.14305.help-gnu-emacs@gnu.org>
2010-03-11 22:48 ` Pascal J. Bourguignon
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