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Message from discussion Implementation Favoritism, a question of Lisp mindsets
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Pascal Costanza  
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 More options May 3 2003, 9:34 am
Newsgroups: comp.lang.lisp
From: Pascal Costanza <costa...@web.de>
Date: Sat, 03 May 2003 15:34:38 +0200
Local: Sat, May 3 2003 9:34 am
Subject: Re: Implementation Favoritism, a question of Lisp mindsets
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In article <030520030610101628%nos...@iam.invalid>,
 Mark Conrad <nos...@iam.invalid> wrote:

> Okay, here is the closure k that I have been talking about:

> (defvar k)

> (let ((x  'big) (y  'daddy))
>     (setq k  #'(lambda () (list x y) )))

> ? (funcall k)
> (BIG DADDY)

> Now, where is that guy who made a statement a few days ago to the
> effect that a closure preserves the bindings, not the values.

> To me they seem to be essentially the same thing.

> Wonder what he meant?

Try the following:

(defvar k)
(defvar setx)
(defvar sety)

(let ((x 'big) (y 'daddy))
  (setq k #'(lambda () (list x y)))
  (setq setx #'(lambda (value) (setq x value)))
  (setq sety #'(lambda (value) (setq y value))))

? (funcall k)
(big daddy)

? (funcall sety 'mummy)
mummy

Try to guess what (funcall k) will print now.

And PLEASE: It's not very constructive that you don't follow the links
people provide to you. See http://www.psg.com/~dlamkins/sl/contents.html, especially lessons 5 and 6.

Do it! Do it now! Take some time to read and understand these things.
There are over 30 chapters in that book. You don't want to post that
much as you do on every single topic, right?

Pascal


 
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