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Re: Mis-features of let


From: Thien-Thi Nguyen
Subject: Re: Mis-features of let
Date: Wed, 20 Apr 2005 16:41:18 +0200
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux)

"rgb" <address@hidden> writes:

> I was under the impression that let must be creating a symbol with
> the name I specified if one didn't already exist.  Many tests seemed
> to confirm this view but some did not, triggering this dialog.

`read' creates symbols (at read time).
`let' binds symbols to values (at evaluation time).

by the time `let' enters the picture, all the symbols that comprise the
form being evaluated have already been created.  they populate, along w/
other atoms like numbers and strings, the leaves of the nested lists in
memory (the form aka tree).

after `let' is done, the tree may or may not remain in memory.  like
anything else (in an emacs session), if nothing points to it, it will be
forgotten at some point.  however, the symbols are not forgotten unless
you explicitly evict them w/ `unintern'.

> Hopefully there are no more such flaws in my understanding.

there is hope indeed (but only by giving up this particular hope :-).
it's a good sign, in any case, when you question your assumptions and
broaden the inquiry.

probably a break from the symbols part in the elisp manual, while you
peruse the `let' or `read' parts, will help you formulate a better bug
report.

thi


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