From: "Drew Adams" <drew.adams@oracle.com>
To: <help-gnu-emacs@gnu.org>, "'Tom Roche'" <Tom_Roche@pobox.com>
Subject: RE: [emacs-lisp newbie] print-something() -> clipboard?
Date: Mon, 21 May 2012 06:24:17 -0700 [thread overview]
Message-ID: <6784456F5E1247D387CCC7C99DA86748@us.oracle.com> (raw)
In-Reply-To: <87boli1ttd.fsf@pobox.com>
> > (defun foo (&optional arg)
> > "..."
> > (interactive "P")
> > (let ((bn ...))
> > (if arg
> > (insert bn)
> > (kill-new bn))))
>
> Thanks! I probably should `let`,
Yes, you should.
> but this works:
>
> (defun print-buffer-name (&optional arg)
> "..."
> (interactive "P")
> (setq bn ...)
> (if arg
> (kill-new bn)
> (insert bn)))
`bn' is a free variable here - by default a global, dynamically scoped variable.
If you or some code that you use defines another variable named `bn' then your
code will suffer from variable capture: You could end up changing the other
variable.
There is NO reason to use `setq' here, and NO reason not to use `let'.
When you suffer from variable capture you don't necessarily realize it, and
debugging the problem (with perhaps farflung symptoms) can be a headache. A
self-imposed headache in this case, for no benefit.
prev parent reply other threads:[~2012-05-21 13:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-18 19:46 [emacs-lisp newbie] print-something() -> clipboard? Tom Roche
2012-05-19 7:19 ` Andreas Röhler
2012-05-20 18:57 ` Tom Roche
2012-05-20 19:20 ` Drew Adams
2012-05-20 20:27 ` Tom Roche
2012-05-21 13:24 ` Drew Adams [this message]
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