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From: Daniel Cerqueira <dan.list@lispclub.com>
Newsgroups: comp.lang.lisp
Subject: McCarthy's eval correction?
Date: Thu, 17 Apr 2025 11:37:09 +0100
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In trying to understand McCarthy's eval, I have one question left
unresolved.  Let me give a code snippet of eval, which is written in
Common Lisp, taken from Paul Graham's draft.

```
(defun eval. (e a)
  (cond
    ...
    ((eq (caar e) 'label)
     (eval. (cons (caddar e) (cdr e))
            (cons (list (cadar e) (car e)) a)))
    ...
    ))
```

I wonder what practical difference does it make to, instead, write eval
like this:

```
(defun eval. (e a)
  (cond
    ...
    ((eq (caar e) 'label)
     (eval. (cons (caddar e) (cdr e))
            (cons (list (cadar e) (caddar e)) a)))
    ...
    ))
```

Anyone?

In my opinion, it makes no practical difference, and this correction
avoids unnecessary double processing.

=2D-=20
The pioneers of a warless world are the youth that
refuse military service. ~ Albert Einstein

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