From: Barry Margolin <barmar@alum.mit.edu>
To: help-gnu-emacs@gnu.org
Subject: Re: Can free variable refers to a lexical environment?
Date: Tue, 09 Mar 2010 13:21:01 -0500 [thread overview]
Message-ID: <barmar-5BFA70.13210109032010@nothing.attdns.com> (raw)
In-Reply-To: 180666d9-2ecb-4d99-a419-739650a8fb3d@c37g2000prb.googlegroups.com
In article
<180666d9-2ecb-4d99-a419-739650a8fb3d@c37g2000prb.googlegroups.com>,
IWAKI Hidekazu <i.hidekazu@gmail.com> wrote:
> Hello,
>
> I need to make a table factory function in emacs with cl extension.
> but I'm scheme user. I'm confusing emacs lisp behavior.
> will you please tell me the emacs lisp's free variable issue.
>
> my table factory function is following code:
> (defun mk-table-instance ()
> (let ((table nil)) ;; create a lexical value `table`
> (defun __temp__ (msg &rest value)
> ;; some operation changes the lexical variable `table`
> (case msg
> ((push) (push (car value) table))
> (otherwise table)))
> (function __temp__)))
> ;; return the `__temp__` procedure with the lexical variable `table`
> ;; i.e. return a closure.
>
> (fset 'table-object (mk-table-instance))
> ;; 'table-object is an unique procedure object.
> (table-object 'push 13)
> ;; my plan => operate an unique `table` variable which was created by
> involving `mk-table-instance`
> ;; real => "Debugger entered--Lisp error: (void-variable
> table)"!!!!!!!
>
> I researched this code. I guess the lexical binded variable `table` in
> `mk-table-instance` procedure refer to the global environment.
> In scheme, the variable refer to the lexical environment.
>
> How to refer to a lexical environment?
Emacs Lisp implements dynamic scoping, not lexical scoping.
You can use lexical-let to emulate lexical binding.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***
next prev parent reply other threads:[~2010-03-09 18:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-09 12:43 Can free variable refers to a lexical environment? IWAKI Hidekazu
2010-03-09 18:21 ` Barry Margolin [this message]
2010-03-10 4:47 ` IWAKI Hidekazu
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